1068 METHODS
Hospital
Practice
Four experienced staff radiologists viewed 45 urogram., each with a short clinical history, on three separate occasions 21 normal and 24 abnormal cases were selected from departmental case-material by one us who did not participate in the case review. The selection of abnormal cases (table i, was based on the relative frequencies of particular abnormal diagnoses observed in the department.’’ The diagnoses were verified at surgery, or by pathological data or at clinical follow up. with clinical and radiological consensus. The normal cases were all verified by prolonged clinical follow-up and by clinical and radiological consensus.
SIMPLIFYING RADIOLOGICAL EXAMINATIONS THE UROGRAM AS A MODEL
BRUCE HILLMAN SAMUEL J. HESSEL ROBERT B. BENAZZI
HERBERT L. ABRAMS STEVEN HERBERT DONALD E. GERSON
Films
Department of Radiology, Harvard Medical School; Peter Bent Brigham Hospital; and Sidney Farber Cancer Institute,
All urograms included a preliminary film, followed bv a bolus injection of 60% ’Renografin’ (meglumine diatrizoate (1-1ml/kg body-weight). The complete radiographic sequence after injection was a coned film of the kidneys at 1 min, a s min abdominal film followed by compression to the midureters, a 10 min anteroposterior and two oblique compression radiographs coned to the kidneys, and a compression-release film at 15 min (table II). To eliminate bias, all radiologists reviewed a one-film examination first, a three-film examination second, and the complete six-film study third after intervening periods of at least 2 months. In the first viewing, the only post-contrast film was a 15 min anteroposterior compression-release radiograph. The second (three films) added the 1 min nephrogram and a 10 mm anteroposterior compression film. The third sequence (six films) included the entire examination (table n).
Boston, Massachusetts, U.S.A.
The diagnostic yield of one and three film urograms was compared with that of complete examinations to determine whether a moderately complex examination could be simplified without loss of important diagnostic information. Although sensitivity was high (88-93%) and was not altered by increasing the complexity of the examination, the definitive disease diagnoses were more accurate with the three film rather than the one film studies. Specificity increased from 69% to 77-80% with the more complex examinations. A strategy based on terminating the examination if the single film urogram is normal with a three-film examination in positive cases might effect considerable savings, both economic and in terms of gonadal radiation dose, without serious diagnostic
Summary
Sensitivity, Specificity, Accuracy
loss. INTRODUCTION
ATTENTION has lately been focused on ways of reducing medical-care expenses,’ of which the cost of diagnostic tests is a major component. Radiological examinations (271 million were done in the United States in 1977 at an estimated cost of over$6000 million) are important both economically and "biologically".2·3 The large number of examinations reflects the difficulty of putting a limit on diagnostic tests considered essential by the referring physician.4 In the absence of a strategy to reduce the total number, important financial and radiation dose savings might be effected by altering the complexity of some examinations. The feasibility of such an approach was explored by one of us (H.L.A.) because of concern for the gonadal .
,
-
and marrow dose in children with vesicoureteral reflux. These patients usually have serial X-ray examinations over a period of years. The urogram was shortened to a single film 8 min after the intravenous injection of contrast agent, in the belief that it would provide the essential information required for management. Subsequent experience indicated that additional films were rarely required. (This change in the routine follow-up paediatric urogram was introduced at the Stanford Medical Center, Palo Alto, California in 1963, when H. L. A. was director of diagnostic radiology.) As an outgrowth of this experience, a study was undertaken to investigate the sensitivity, specificity, and diagnostic value of the intravenous urogram in three different formats of varying special attention was paid to the loss of diagnostic information associated with a simplified examination.
The radiologists reported each case as normal or abnormal and recorded their degree of confidence in their decision on a scale of 1-3 (l=definite, 2=probable, 3=possible). In cases considered abnormal, a definitive diagnosis was made, and the confidence level indicated. The forms were collected and tabulated by one of the team who was not involved with film interTABLE I-ÆTIOLOGY OF ABNORMAL CASES
TABLE
II-1, 3,
AND
6
FILM EXAMINATION
complexity;
A. P. =anteroposterior. K. U. B. =Kidney-ureter-bladder.
SEQUENCE
1069 was calculated by including as abnormal all examinations considered definitely, probably, or possibly abnormal, and pooling the data. Sensitivity (true-positive rate) is defined as the number of correct positive diagnoses divided by the number of patients with disease. Specificity was calculated by including as normal all examinations considered definitely, probably, or possibly normal, and pooling the data. Specificity (true-negative rate) is defined as the number of correct normal diagnoses divided by the number of patients without disease. Accuracy is defined as the total number of correct diagnoses divided by the total patient population. To assess differences in performance among readers and
pretation. Sensitivity
receiver-operating-characteristic analysis was una curve plotted depicting the relation between positives and false positives at all confidence levels for
readings,
a
dertaken and true
Proportion of Negative Cases Read
each reader and for the group.
Economic and Biological
(Radiation Exposure) Costs
1, 3,
TABLE III-SENSITIVITY AND SPECIFICITY OF
AND
6
FILM
UROGRAMS
I
I
I
I
I
I
Positive
Receiver-operating-characteristic curves. These
Economic.-In our department intravenous urography costs$111. The total cost incorporates technical factors such as X-ray film, contrast agent, and other supplies, technologist and support staff time, equipment leases and maintenance, provision for overheads, bad debts, free care, and contractual allowance, and the professional cost of interpreting the films. The costs of one and three film urograms were estimated at $51.50 and$78, respectively. These costs were then used to compare the economics of the full (six) film approach with a new strategy based on one and three film examinations. This strategy was based on conclusions arrived at after the analysis
as
are
group
curves
from the four observers for
single-film,
three-film, and complete six-film examinations. The five data points on each curve represent the proportions of truly positive cases (n=24) and truly negative cases (n=21) called positive when successively lessconfidence criteria are used as cut-offs for defining "positive" reports. The curves have been smoothed by a maximum-likelihood procedure that assumes the true curve is a linear function when the true and false detection-rates are transformed into their equivalent deviates of the standard normal distribution. The vertical bars indicate ±1S.E. of the predicted true-detection rate for the fitted single-film curve (heavy line) at selected values of the assumed false-positive rates.
stringent
all readings (see figure). The receiver-operating-characteristic curves for the three readings were statistically indistinguishable with standard deviations which overlapped at all points (see figure). Definitive disease diagnoses were correct in 75% of the single film, 87% of the three film, and 84% of the six film urograms (table Iv). The correctness of explicit diagnoses improved for all four radiologists with the three compared with the one film study. Only one radiologist improved with the full study compared with the three-film urogram. DISCUSSION
performance. The calculations estimated the annual cost saving based on 2320 urograms done during a 12-month period, of which 65% were normal and 35% showed a significant abnormality.5 of reader
Radiation.-Gonadal radiation doses for one, three, and six films were calculated from median doses for the specific films. The estimated dose for the one-film examination was 200 mrad in males and 440 mrad in females; for the three-film study the figures were 301 mrad m males and 740 mrad in females; and for the six-film study doses were 333 mrad in males and 960 mrad in females. Calculations analogous to those on economic cost were performed to determine the annual savings in gonadal radiation. RESULTS
The concept of defining referral criteria for radiological examinations to avoid unnecessary procedures seems logical but has proved difficult to apply.6 Some studies have shown that low-yield indications for particular examinations can be crystallised,’ and that reasonable criteria, when applied systematically, may alter utilisation.7 Other investigations, by contrast, have indicated that examinations such as barium enema and urography are ses
being appropriately requested.5,8,9 Two recent analydiagnostic efficacy of the urogram support the
of the
TABLE
IV-"DEFINITIVENESS"*
OF DISEASE DIAGNOSES AMONG
CASES CORRECTLY CONSIDERED POSITIVE ON
when the number of films increased from one to six and when all confidence levels were included (table m) while sensitivity hardly altered. Accuracy of the one, three, and six-film examinations was 82%, 83‘, and 85%, respectively. No consistent differences in performance were noted among the four readers. When the reviewers were certain that disease was present ("definitely abnormal"), they detected 75-81% of the true-positives, with a false-positive rate of 6 % for
Specificity
rose
slightly
UROGRAMS
1, 3,
AND
6
FILM
(POOLED DATA)
*"Definitiveness" refers, not simply to detecting the abnormal, but rather to indicating the pathological nature of the abnormality with precision-i.e., whether carcinoma, cyst, pyelonephrius, papillary necrosis, and so on.
1070 concept that in most cases it has a major impact on final diagnostic decisions. 10,11 If the number of patients referred for investigation cannot be reduced then perhaps the number of films per examination should be looked at. In this study, a single 15 min compression-release film provided enough information to identify over 90% of the patients with disease (sensitivity), a figure not increased by the three and six film examinations. The one-film study also excluded 69, of the patients who were disease-free with a modest increase in specificity on the three and full film studies. Finally, the three-film examination increased the likelihood of defining the explicit nature of the underlying abnormality for all readers which was not further enhanced by the complete study. These findings suggest an approach to intravenous urography which might reduce cost and radiation without impairing diagnostic efficacy. We would suggest the following strategy (table v):
(1)
A
10 min film should be done in in which prior renal abnormality
single post-compression
all new cases and in all cases has been demonstrated (follow-up urogram). (2) If the 10 min post-compression film is normal in new cases, or if it provides adequate follow-up information on known abnormal cases, the examination should be considered complete and should be discontinued. (3) If the film is considered abnormal, a second injection should be given; a 1 min nephrogram film should be taken and compression applied immediately thereafter, followed by an 8 min compression film. (4) If the urinary tract is adequately demonstrated, the examination should be discontinued. (5) If the findings are uncertain, additional films should be obtained. TABLE V-NEW
STRATEGY
TABLE VI-COST COMPARISON FOR PETER
BENT BRIGHAM
HOSPITAL
TABLE VII-MEAN GONADAL RADIATION
(MRAD) PER PATIENT
I
I
*Assumes 70‘ of all patients require 1-film examination only and remainder 3-film study. tAssumes 51% of all patients (33‘ of new patients) require 1-film examination only.
This strategy
$119 000 (or
might
lead
46% of the
to
cost
saving of of urography) in our an
annual
department (table vi). Projected on a national scale, the savings might well surpass$300 million. (In 1970, out of 129 million X-ray examinations done in the United States, 4 million were urograms (about 3 %).12 In 1977, 271 million X-ray examinations were done,2 of which 3% would represent 8 million urograms. If the total cost were$800 million a 46% saving would amount to$368 million.) A considerable reduction in gonadal radiation exposure (24% in males, 46% in females) would also be achieved (table vn). It may be argued that radiologists - knowing that interpreting a single film as normal would end the study-might shift to more stringent criteria and re-inject all but those considered normal at a high-confidence level (33% of all normals on the onefilm reading). Although the financial and radiation savings are less than when all confidence levels are considered, they are still appreciable (table vn). Despite the potential for financial savings and lower radiation exposure, physician behaviour in the conduct of urographic examinations may not necessarily change. For one thing, verification of our findings may reasonably be asked for before radiologists relinquish methods which have been clinically satisfactory. Furthermore the primary function of the radiologist is to resolve diagnostic uncertainty, and in fulfilling this role he will often require a level of certainty in his own diagnosis which entails the acquisition of redundant information. What may be of greater importance than any immediate impact on the format of the urogram is the potential use of data of this sort to plan strategies when budgets are tight. For example, if funds available for urography are halved, how will they be expended? BB’ill half the patients receive the whole examination?—or will a screening process be developed to permit concentration on clinically indicated urograms while proscribing further films in patients with a normal one-film study? To a major degree, these are social and economic as
well
to
supply
as
medical questions, and the data base needed rational and medically sound answers clear!’,
needs enlargement. *Assumes 70’, of all patients require only 1-film examination and remainder 3-film study. tAssumes 51’f of all patients (33‘‘ of new patients) require only 1-film examination.
Supported m part by U.S. Public Health Service grant, GMIS GM01910, and GM23891. S. J. H. is the recipient of career development ment
award HL00479 from the National Institutes of Health.
Requests for repnnts should be addressed
to
H.
L. A , Department
1071
professionals according to a formula that enabled the clinics to meet their operating expenses.7 Federal regulations issued in 1974 defined "critical health manpower shortage areas" and limited N.H.S.C. placements to them. Other regulations stipulated that a memorandum of agreement signed by the community board would constitute the contract between the Government and the N.H.S.C. area. 20 placements were made in 16 communities in January, 1972, followed by 162 more in the summer of 1972. Most of those appointed (138) were physicians, as has been the case throughout the programme. The N.H.S.C. grew slowly, showing that the recruitment of physicians at modest P.H.S. salaries for service in difficult areas would not produce a large field force. Knowing this, Congress established the P.H.S.-N.H.S.C. scholarship programme,8 by which the P.H.S. would pay for professional school tuition and a stipend in return for which the student would incur a year-for-year service obligation. The first scholarships were awarded in February, 1974, and the first scholarship holders to join the N.H.S.C. did so in 1976. The political climate of the programme’s early years was difficult. Social programmes of all sorts were being closely scrutinised by the Nixon administration, but the Act setting up the N.H.S.C. had been signed by President Nixon, and the N.H.S.C. enjoyed continued congressional support. The N.H.S.C. therefore grew despite the prevailing political climate. The Nixon and Ford administrations, however, had a considerable impact on the style and priorities of the early N.H.S.C. Heavy emphasis was placed on the private-practice potential of the programme. Physicians were urged to go into private practice at the end of their tour of duty. Sites were frequently selected and developed with this in mind. Most placements were small (one or two physician) practices, and 95C,;c of them were in rural areas reflecting the difficulty of applying the fee-for-service model to inner city areas. Urban health, the health of ethnic minorities, or that of labouring groups such as migrant workers were addressed only randomly. There was no formal coordination between the N.H.S.C. and other Federal grant programmes or State, county, or municipal health services.
of Radiology, Harvard Medical School, 25 Shattuck Street, Boston, Massachusetts 02115, U.S.A. REFERENCES 1 Mechanic, D. New Engl J. Med. 1978, 298, 249. 2 Derzon, R A Paper read at international conference
Radiological Technology in
San
on
on the Health Care, Research, and
Impact of New Teaching, held
Francisco, in 1978
Rogers, P. G. Paper read at national conference on Referral Criteria for X-Ray Examinations, held in Washington, D.C., in October, 1978. 4. Bell, R S., Loop, J. W. New Engl. J. Med. 1971, 284, 236. 5 Mellins, H. Z., McNeil, B. J., Abrams, H. L., Van Houten, F. X., Murphy, M. A , Korngold, E. Radiology 1979, 130, 293. 6. Abrams, H. L. Paper read at national conference on Referral Criteria for X-Ray Examinations, held m Washington, D. C., in October, 1978. 7 Phillips, L. A. A Study of the Effect of High Yield Criteria for Emergency Room Skull Radiography. H. E. W. publication (FDA) 73-8069, 1978. 8 MacEwan, D. W, Kavanagh, S., Chow, P., Tishler, J. M. Radiology 1978, 126, 39 9 Gerson, D E , Lewicki, A. M., McNeil, B. J., Abrams, H. L., Korngold, E. ibid. 1979, 130, 297. 10. Thornbury, J R., Fryback, D. G., Edwards, W. ibid. 1975, 114, 561. 11. Lusted, L. A Study of the Efficacy of Diagnostic Radiologic Procedures: final report on diagnostic efficacy. American College of Radiology, 1977. 12. Department of Health, Education and Welfare. Population Exposure to X-rays, U S, 1970; table 25, p. 92. D.H.E.W. publication FDA 73-8047. 3.
Primary Care THE NATIONAL HEALTH SERVICE CORPS FITZHUGH MULLAN Director National Health Service
Corps, Public Health
Service, Health Services Administration, Department of Health, Welfare, and Education, Rockville, Maryland 20857, U.S.A.
THE National Health Service Corps (N.H.S.C.) was established by the Emergency Health Personnel Act of 1970, by which the United States Public Health Service (P.H.S.) could meet the health-care needs of underserved civilian populations. Although the P.H.S. has had a long record of health-service delivery to statutorily designated populations (American Indians, the Merchant Marine, Federal prisoners), this was the first time that federally employed physicians were to provide complete medical services to the general population. ’
HISTORY
1970 evidence had accumulated that the United States had too few physicians and that they were unevenly distributed. 1-3 Not only health planners and politicians but also many medical students and young physicians were aware that many areas had an inadequate medical service.4,5 The Emergency Health Personnel Act, passed on Dec. 31, 1970,6 called for the P.H.S. to recruit physicians and other health professionals for areas that were short of physicians. The programme was a joint community and government project. The P.H.S. would supply the health professionals while the community would provide office space, other personnel, and the necessary overheads. Patients had to pay for services at a rate fixed by the community board, but no one was to be denied service because they were unable to pay. This resulted in slidmg fee schedules and lenient billing policies. The community clinics, in turn, were obliged to reimburse the Federal Treasury for part of the cost of the N.H.S.C.
CURRENT STATUS
By
.
Since 1977, a number of important changes have taken place. The Health Professions Educational Assistance Act,9 passed on Oct. 12, 1976, re-established and augmented the scholarship programme, which became simply the N.H.S.C. Scholarship Program. The new law also broadened the methodology for defining health manpower shortage areas, so that there are now almost 1200 counties, census tracts, trade areas, and neighbourhoods eligible for N.H.S.C. assistance.’° Some 25 000 000 Americans live in these areas. The law redefined a number of aspects of the scholarship programme and, most importantly, increased the authorisation for the programme such that its potential for growth was considerable. Finally, the law mentions facilities such as State mental hospitals and State prisons as appropriate placements for members of the N.H.S.C., suggesting formallv for the first time that the N.H.S.C. become involved in institutional work.
Hospital
Practice
Four experienced staff radiologists viewed 45 urogram., each with a short clinical history, on three separate occasions 21 normal and 24 abnormal cases were selected from departmental case-material by one us who did not participate in the case review. The selection of abnormal cases (table i, was based on the relative frequencies of particular abnormal diagnoses observed in the department.’’ The diagnoses were verified at surgery, or by pathological data or at clinical follow up. with clinical and radiological consensus. The normal cases were all verified by prolonged clinical follow-up and by clinical and radiological consensus.
SIMPLIFYING RADIOLOGICAL EXAMINATIONS THE UROGRAM AS A MODEL
BRUCE HILLMAN SAMUEL J. HESSEL ROBERT B. BENAZZI
HERBERT L. ABRAMS STEVEN HERBERT DONALD E. GERSON
Films
Department of Radiology, Harvard Medical School; Peter Bent Brigham Hospital; and Sidney Farber Cancer Institute,
All urograms included a preliminary film, followed bv a bolus injection of 60% ’Renografin’ (meglumine diatrizoate (1-1ml/kg body-weight). The complete radiographic sequence after injection was a coned film of the kidneys at 1 min, a s min abdominal film followed by compression to the midureters, a 10 min anteroposterior and two oblique compression radiographs coned to the kidneys, and a compression-release film at 15 min (table II). To eliminate bias, all radiologists reviewed a one-film examination first, a three-film examination second, and the complete six-film study third after intervening periods of at least 2 months. In the first viewing, the only post-contrast film was a 15 min anteroposterior compression-release radiograph. The second (three films) added the 1 min nephrogram and a 10 mm anteroposterior compression film. The third sequence (six films) included the entire examination (table n).
Boston, Massachusetts, U.S.A.
The diagnostic yield of one and three film urograms was compared with that of complete examinations to determine whether a moderately complex examination could be simplified without loss of important diagnostic information. Although sensitivity was high (88-93%) and was not altered by increasing the complexity of the examination, the definitive disease diagnoses were more accurate with the three film rather than the one film studies. Specificity increased from 69% to 77-80% with the more complex examinations. A strategy based on terminating the examination if the single film urogram is normal with a three-film examination in positive cases might effect considerable savings, both economic and in terms of gonadal radiation dose, without serious diagnostic
Summary
Sensitivity, Specificity, Accuracy
loss. INTRODUCTION
ATTENTION has lately been focused on ways of reducing medical-care expenses,’ of which the cost of diagnostic tests is a major component. Radiological examinations (271 million were done in the United States in 1977 at an estimated cost of over$6000 million) are important both economically and "biologically".2·3 The large number of examinations reflects the difficulty of putting a limit on diagnostic tests considered essential by the referring physician.4 In the absence of a strategy to reduce the total number, important financial and radiation dose savings might be effected by altering the complexity of some examinations. The feasibility of such an approach was explored by one of us (H.L.A.) because of concern for the gonadal .
,
-
and marrow dose in children with vesicoureteral reflux. These patients usually have serial X-ray examinations over a period of years. The urogram was shortened to a single film 8 min after the intravenous injection of contrast agent, in the belief that it would provide the essential information required for management. Subsequent experience indicated that additional films were rarely required. (This change in the routine follow-up paediatric urogram was introduced at the Stanford Medical Center, Palo Alto, California in 1963, when H. L. A. was director of diagnostic radiology.) As an outgrowth of this experience, a study was undertaken to investigate the sensitivity, specificity, and diagnostic value of the intravenous urogram in three different formats of varying special attention was paid to the loss of diagnostic information associated with a simplified examination.
The radiologists reported each case as normal or abnormal and recorded their degree of confidence in their decision on a scale of 1-3 (l=definite, 2=probable, 3=possible). In cases considered abnormal, a definitive diagnosis was made, and the confidence level indicated. The forms were collected and tabulated by one of the team who was not involved with film interTABLE I-ÆTIOLOGY OF ABNORMAL CASES
TABLE
II-1, 3,
AND
6
FILM EXAMINATION
complexity;
A. P. =anteroposterior. K. U. B. =Kidney-ureter-bladder.
SEQUENCE
1069 was calculated by including as abnormal all examinations considered definitely, probably, or possibly abnormal, and pooling the data. Sensitivity (true-positive rate) is defined as the number of correct positive diagnoses divided by the number of patients with disease. Specificity was calculated by including as normal all examinations considered definitely, probably, or possibly normal, and pooling the data. Specificity (true-negative rate) is defined as the number of correct normal diagnoses divided by the number of patients without disease. Accuracy is defined as the total number of correct diagnoses divided by the total patient population. To assess differences in performance among readers and
pretation. Sensitivity
receiver-operating-characteristic analysis was una curve plotted depicting the relation between positives and false positives at all confidence levels for
readings,
a
dertaken and true
Proportion of Negative Cases Read
each reader and for the group.
Economic and Biological
(Radiation Exposure) Costs
1, 3,
TABLE III-SENSITIVITY AND SPECIFICITY OF
AND
6
FILM
UROGRAMS
I
I
I
I
I
I
Positive
Receiver-operating-characteristic curves. These
Economic.-In our department intravenous urography costs$111. The total cost incorporates technical factors such as X-ray film, contrast agent, and other supplies, technologist and support staff time, equipment leases and maintenance, provision for overheads, bad debts, free care, and contractual allowance, and the professional cost of interpreting the films. The costs of one and three film urograms were estimated at $51.50 and$78, respectively. These costs were then used to compare the economics of the full (six) film approach with a new strategy based on one and three film examinations. This strategy was based on conclusions arrived at after the analysis
as
are
group
curves
from the four observers for
single-film,
three-film, and complete six-film examinations. The five data points on each curve represent the proportions of truly positive cases (n=24) and truly negative cases (n=21) called positive when successively lessconfidence criteria are used as cut-offs for defining "positive" reports. The curves have been smoothed by a maximum-likelihood procedure that assumes the true curve is a linear function when the true and false detection-rates are transformed into their equivalent deviates of the standard normal distribution. The vertical bars indicate ±1S.E. of the predicted true-detection rate for the fitted single-film curve (heavy line) at selected values of the assumed false-positive rates.
stringent
all readings (see figure). The receiver-operating-characteristic curves for the three readings were statistically indistinguishable with standard deviations which overlapped at all points (see figure). Definitive disease diagnoses were correct in 75% of the single film, 87% of the three film, and 84% of the six film urograms (table Iv). The correctness of explicit diagnoses improved for all four radiologists with the three compared with the one film study. Only one radiologist improved with the full study compared with the three-film urogram. DISCUSSION
performance. The calculations estimated the annual cost saving based on 2320 urograms done during a 12-month period, of which 65% were normal and 35% showed a significant abnormality.5 of reader
Radiation.-Gonadal radiation doses for one, three, and six films were calculated from median doses for the specific films. The estimated dose for the one-film examination was 200 mrad in males and 440 mrad in females; for the three-film study the figures were 301 mrad m males and 740 mrad in females; and for the six-film study doses were 333 mrad in males and 960 mrad in females. Calculations analogous to those on economic cost were performed to determine the annual savings in gonadal radiation. RESULTS
The concept of defining referral criteria for radiological examinations to avoid unnecessary procedures seems logical but has proved difficult to apply.6 Some studies have shown that low-yield indications for particular examinations can be crystallised,’ and that reasonable criteria, when applied systematically, may alter utilisation.7 Other investigations, by contrast, have indicated that examinations such as barium enema and urography are ses
being appropriately requested.5,8,9 Two recent analydiagnostic efficacy of the urogram support the
of the
TABLE
IV-"DEFINITIVENESS"*
OF DISEASE DIAGNOSES AMONG
CASES CORRECTLY CONSIDERED POSITIVE ON
when the number of films increased from one to six and when all confidence levels were included (table m) while sensitivity hardly altered. Accuracy of the one, three, and six-film examinations was 82%, 83‘, and 85%, respectively. No consistent differences in performance were noted among the four readers. When the reviewers were certain that disease was present ("definitely abnormal"), they detected 75-81% of the true-positives, with a false-positive rate of 6 % for
Specificity
rose
slightly
UROGRAMS
1, 3,
AND
6
FILM
(POOLED DATA)
*"Definitiveness" refers, not simply to detecting the abnormal, but rather to indicating the pathological nature of the abnormality with precision-i.e., whether carcinoma, cyst, pyelonephrius, papillary necrosis, and so on.
1070 concept that in most cases it has a major impact on final diagnostic decisions. 10,11 If the number of patients referred for investigation cannot be reduced then perhaps the number of films per examination should be looked at. In this study, a single 15 min compression-release film provided enough information to identify over 90% of the patients with disease (sensitivity), a figure not increased by the three and six film examinations. The one-film study also excluded 69, of the patients who were disease-free with a modest increase in specificity on the three and full film studies. Finally, the three-film examination increased the likelihood of defining the explicit nature of the underlying abnormality for all readers which was not further enhanced by the complete study. These findings suggest an approach to intravenous urography which might reduce cost and radiation without impairing diagnostic efficacy. We would suggest the following strategy (table v):
(1)
A
10 min film should be done in in which prior renal abnormality
single post-compression
all new cases and in all cases has been demonstrated (follow-up urogram). (2) If the 10 min post-compression film is normal in new cases, or if it provides adequate follow-up information on known abnormal cases, the examination should be considered complete and should be discontinued. (3) If the film is considered abnormal, a second injection should be given; a 1 min nephrogram film should be taken and compression applied immediately thereafter, followed by an 8 min compression film. (4) If the urinary tract is adequately demonstrated, the examination should be discontinued. (5) If the findings are uncertain, additional films should be obtained. TABLE V-NEW
STRATEGY
TABLE VI-COST COMPARISON FOR PETER
BENT BRIGHAM
HOSPITAL
TABLE VII-MEAN GONADAL RADIATION
(MRAD) PER PATIENT
I
I
*Assumes 70‘ of all patients require 1-film examination only and remainder 3-film study. tAssumes 51% of all patients (33‘ of new patients) require 1-film examination only.
This strategy
$119 000 (or
might
lead
46% of the
to
cost
saving of of urography) in our an
annual
department (table vi). Projected on a national scale, the savings might well surpass$300 million. (In 1970, out of 129 million X-ray examinations done in the United States, 4 million were urograms (about 3 %).12 In 1977, 271 million X-ray examinations were done,2 of which 3% would represent 8 million urograms. If the total cost were$800 million a 46% saving would amount to$368 million.) A considerable reduction in gonadal radiation exposure (24% in males, 46% in females) would also be achieved (table vn). It may be argued that radiologists - knowing that interpreting a single film as normal would end the study-might shift to more stringent criteria and re-inject all but those considered normal at a high-confidence level (33% of all normals on the onefilm reading). Although the financial and radiation savings are less than when all confidence levels are considered, they are still appreciable (table vn). Despite the potential for financial savings and lower radiation exposure, physician behaviour in the conduct of urographic examinations may not necessarily change. For one thing, verification of our findings may reasonably be asked for before radiologists relinquish methods which have been clinically satisfactory. Furthermore the primary function of the radiologist is to resolve diagnostic uncertainty, and in fulfilling this role he will often require a level of certainty in his own diagnosis which entails the acquisition of redundant information. What may be of greater importance than any immediate impact on the format of the urogram is the potential use of data of this sort to plan strategies when budgets are tight. For example, if funds available for urography are halved, how will they be expended? BB’ill half the patients receive the whole examination?—or will a screening process be developed to permit concentration on clinically indicated urograms while proscribing further films in patients with a normal one-film study? To a major degree, these are social and economic as
well
to
supply
as
medical questions, and the data base needed rational and medically sound answers clear!’,
needs enlargement. *Assumes 70’, of all patients require only 1-film examination and remainder 3-film study. tAssumes 51’f of all patients (33‘‘ of new patients) require only 1-film examination.
Supported m part by U.S. Public Health Service grant, GMIS GM01910, and GM23891. S. J. H. is the recipient of career development ment
award HL00479 from the National Institutes of Health.
Requests for repnnts should be addressed
to
H.
L. A , Department
1071
professionals according to a formula that enabled the clinics to meet their operating expenses.7 Federal regulations issued in 1974 defined "critical health manpower shortage areas" and limited N.H.S.C. placements to them. Other regulations stipulated that a memorandum of agreement signed by the community board would constitute the contract between the Government and the N.H.S.C. area. 20 placements were made in 16 communities in January, 1972, followed by 162 more in the summer of 1972. Most of those appointed (138) were physicians, as has been the case throughout the programme. The N.H.S.C. grew slowly, showing that the recruitment of physicians at modest P.H.S. salaries for service in difficult areas would not produce a large field force. Knowing this, Congress established the P.H.S.-N.H.S.C. scholarship programme,8 by which the P.H.S. would pay for professional school tuition and a stipend in return for which the student would incur a year-for-year service obligation. The first scholarships were awarded in February, 1974, and the first scholarship holders to join the N.H.S.C. did so in 1976. The political climate of the programme’s early years was difficult. Social programmes of all sorts were being closely scrutinised by the Nixon administration, but the Act setting up the N.H.S.C. had been signed by President Nixon, and the N.H.S.C. enjoyed continued congressional support. The N.H.S.C. therefore grew despite the prevailing political climate. The Nixon and Ford administrations, however, had a considerable impact on the style and priorities of the early N.H.S.C. Heavy emphasis was placed on the private-practice potential of the programme. Physicians were urged to go into private practice at the end of their tour of duty. Sites were frequently selected and developed with this in mind. Most placements were small (one or two physician) practices, and 95C,;c of them were in rural areas reflecting the difficulty of applying the fee-for-service model to inner city areas. Urban health, the health of ethnic minorities, or that of labouring groups such as migrant workers were addressed only randomly. There was no formal coordination between the N.H.S.C. and other Federal grant programmes or State, county, or municipal health services.
of Radiology, Harvard Medical School, 25 Shattuck Street, Boston, Massachusetts 02115, U.S.A. REFERENCES 1 Mechanic, D. New Engl J. Med. 1978, 298, 249. 2 Derzon, R A Paper read at international conference
Radiological Technology in
San
on
on the Health Care, Research, and
Impact of New Teaching, held
Francisco, in 1978
Rogers, P. G. Paper read at national conference on Referral Criteria for X-Ray Examinations, held in Washington, D.C., in October, 1978. 4. Bell, R S., Loop, J. W. New Engl. J. Med. 1971, 284, 236. 5 Mellins, H. Z., McNeil, B. J., Abrams, H. L., Van Houten, F. X., Murphy, M. A , Korngold, E. Radiology 1979, 130, 293. 6. Abrams, H. L. Paper read at national conference on Referral Criteria for X-Ray Examinations, held m Washington, D. C., in October, 1978. 7 Phillips, L. A. A Study of the Effect of High Yield Criteria for Emergency Room Skull Radiography. H. E. W. publication (FDA) 73-8069, 1978. 8 MacEwan, D. W, Kavanagh, S., Chow, P., Tishler, J. M. Radiology 1978, 126, 39 9 Gerson, D E , Lewicki, A. M., McNeil, B. J., Abrams, H. L., Korngold, E. ibid. 1979, 130, 297. 10. Thornbury, J R., Fryback, D. G., Edwards, W. ibid. 1975, 114, 561. 11. Lusted, L. A Study of the Efficacy of Diagnostic Radiologic Procedures: final report on diagnostic efficacy. American College of Radiology, 1977. 12. Department of Health, Education and Welfare. Population Exposure to X-rays, U S, 1970; table 25, p. 92. D.H.E.W. publication FDA 73-8047. 3.
Primary Care THE NATIONAL HEALTH SERVICE CORPS FITZHUGH MULLAN Director National Health Service
Corps, Public Health
Service, Health Services Administration, Department of Health, Welfare, and Education, Rockville, Maryland 20857, U.S.A.
THE National Health Service Corps (N.H.S.C.) was established by the Emergency Health Personnel Act of 1970, by which the United States Public Health Service (P.H.S.) could meet the health-care needs of underserved civilian populations. Although the P.H.S. has had a long record of health-service delivery to statutorily designated populations (American Indians, the Merchant Marine, Federal prisoners), this was the first time that federally employed physicians were to provide complete medical services to the general population. ’
HISTORY
1970 evidence had accumulated that the United States had too few physicians and that they were unevenly distributed. 1-3 Not only health planners and politicians but also many medical students and young physicians were aware that many areas had an inadequate medical service.4,5 The Emergency Health Personnel Act, passed on Dec. 31, 1970,6 called for the P.H.S. to recruit physicians and other health professionals for areas that were short of physicians. The programme was a joint community and government project. The P.H.S. would supply the health professionals while the community would provide office space, other personnel, and the necessary overheads. Patients had to pay for services at a rate fixed by the community board, but no one was to be denied service because they were unable to pay. This resulted in slidmg fee schedules and lenient billing policies. The community clinics, in turn, were obliged to reimburse the Federal Treasury for part of the cost of the N.H.S.C.
CURRENT STATUS
By
.
Since 1977, a number of important changes have taken place. The Health Professions Educational Assistance Act,9 passed on Oct. 12, 1976, re-established and augmented the scholarship programme, which became simply the N.H.S.C. Scholarship Program. The new law also broadened the methodology for defining health manpower shortage areas, so that there are now almost 1200 counties, census tracts, trade areas, and neighbourhoods eligible for N.H.S.C. assistance.’° Some 25 000 000 Americans live in these areas. The law redefined a number of aspects of the scholarship programme and, most importantly, increased the authorisation for the programme such that its potential for growth was considerable. Finally, the law mentions facilities such as State mental hospitals and State prisons as appropriate placements for members of the N.H.S.C., suggesting formallv for the first time that the N.H.S.C. become involved in institutional work.
