Variability in Interpretation of Pulmonary Function Tests* leffrey Cary, M.D.;O ° Ion Huseby, Al.D.;t Bruce CulV81', M.D.;t
and CarlKosanke, Ir.*
We asked 26 pulmonary physicians to interpret results of ten consecutive pulmonary function tests from one laboratory. There was frequent disagreement in tIIeir assessment of respiratory impairment. This is likely due to the variety of criteria for gradiDg the severity of ob-
structive and restrictive defedL Since the .......ve interpretatioD of pulIDo.., faactlon data may bdlueace patient care, playsIeIaDs should eooslder the ......CIII magnitude of tile d.....ementl, 88 weD • the deserlptive terms appHed.
The descriptive terms used in the interpretation of pulmonary function test results can be important since the conclusions drawn from the studies not only may influence decisions about a patient's em-
The responses were analyzed by comparing the interpretation from each physician to every other interpretation for the same patient. Each comparison was graded as either agreeing with another comparison or as differing by one (mild to moderate) or two categories (mild to severe). All ten patients under consideration had spirometric tests, and since there were 13 pulmonary physicians from each group who returned their questionnaires, there were 78 possible comparisons for each patient or 780 total comparisons for obstructive disease. For restrictive lung disease, only the five patients who had tests of total lung capacity measured were considered, so that there were 390 total comparisons available for restrictive disease in each physician-group.
For editorial comment, see page 377
ployability and insurability, but also color the attitude of the referring physician toward his patient. We recognized that there was a good deal of disagreement present in the narrative interpretation of similar data from pulmonary function tests by the physicians in our division, so we designed a study to assess the variability in interpretation of pulmonary function test results by respiratory disease physicians using their personal criteria for test interpretation. METHODS
We asked the members of the respiratory disease staff and fellows from the University of Washington (UW) and practicing chest physicians in the state of Washington to interpret ten consecutive pulmonary function tests (PFT ) from one laboratory. The tests were sequential and not selected to demonstrate specific points or to include diJlicult problems. Only the age, height, weight, predicted flow rates and lung volumes and the physiologic data from each patient were given to the interpreting physicians. The physicians were not biased by more detailed clinical information, physical examinations, or presumptive diagnosis. The interpretations were standardized by asking the physicians to identify and grade the severity of any obsbuctive or restrictive lung disease by checking the appropriate boxes titled: none present, mild, moderate or severe disease. ·From the Division of Respiratory Diseases US Public Health Service Hospital, ana the Division 01 Respiratory Diseases, University of Washington, Seattle. Presented at the 43rd Annual Scientific Assembly, American College of Chest Physicians, Las Vegas, October 30November 3, 1977. oOSenior FeJlow. t Assistant Professor. tPulmonary Technician. Manuscript received November 6; revision accepted December 19. Reprint requests: Dr. Huseby, USPHS Hospital, Seattle 98114
CHEST, 76: 4, OCTOBER, 1979
RESULTS
Table 1 summarizes the results of the study. There was a striking frequency of disagreement in the interpretation of the pulmonary function tests. The magnitude of the disagreements was no different whether the physicians had considerable interaction as in the university group, or practiced independently, as in the statewide group. DISCUSSION
A review of the published oriteria'" for the interpretation of obstructive and restrictive lung disease
Obstructive Disease Total Compared Agree Differ X 1 Differ X 2
Restrictive Disease Total Compared Agree
Differ X 1 Differ X 2
University of Washington
State of Washington
780 57% 41%
780 60% 37%
2%
390 63% 32% 5%
3% 300
65% 32%
3%
INTERPRETATION OF PULMONARY FUNCTION TESTS 389
Gaensler 1966
ACCP 1967
Ellis· 1975
Table 3-R.'ricIiH Di.ea.e Ca'e«orie. U.in. To'al Lan. Capaci',.
Utah 1975
80
o
70 FEV,/VC
NORMAL
•
MILO
~
MODERATE
B SEVERE
60
* FOR A PREO F[V,/VC .80~
50
40 FIGURE 1. Variation in obstmctive disease categories using FEV1/VC ratios. 1 - 4
provides insight into the results of the study. Figure 1 summarizes the suggested categories of obstructive disease from four sources. l-4 The criteria of Ellis and colleagues' were presented as percentages of the predicted FEVlIve ratio and for the purposes of this comparison we selected a predicted FEV 1/ VC ratio of 80 percent. In the range of FEVI/VC ratios from 80 percent to 40 percent there is complete agreement only for two narrow bands (67-69 percent, 52-59 percent). Thus, it is not surprising that a large number of the responses in our survey differed by one category. The available criteria for grading restrictive lung disease show similar disagreements. Table 2 shows the suggested levels for describing resbictive disease based on vital capacity and Table 3 gives similar infonnation when total lung capacity is known. In reviewing the responses to this study as well as our own experience, three problems were noted to cause disagreements: 1.- FEVI/VC vs FEVI. We have reviewed four criteria for obstruction based on FEVI/VC which are useful for excluding the effect of variation in VC, but with advanced disease, the functional impairment may correlate better with FEVI than the ratio (eg FEVI/VC of 1.012.0 = 50 percent vs 1.2/3.6 = 33 percent). 2. Combined abnormalities. It is quite possible, Table
2-R~'ricd"e
DiNaae Cale«orie. U.in .. J'i'a' Capaci',. Gaensler and Wright t
Ellis and Colleagues,
Normal
>79%
>79%
Mild
60%-79%
640/0-79 %
Moderate
500/0-59%
440/0-63%
Severe
Pred
390 CARY ET AL
Kanner and Morris,
Ellis and Colleagues, Normal
TLC>79%
TLC>81%
Mild
TLC 640/0-79% + VC >63%
TLC 66%-81 %
Moderate TLC 44%-79%+VC >44%-63% TLC 51%-65% Severe
TLC
and CarlKosanke, Ir.*
We asked 26 pulmonary physicians to interpret results of ten consecutive pulmonary function tests from one laboratory. There was frequent disagreement in tIIeir assessment of respiratory impairment. This is likely due to the variety of criteria for gradiDg the severity of ob-
structive and restrictive defedL Since the .......ve interpretatioD of pulIDo.., faactlon data may bdlueace patient care, playsIeIaDs should eooslder the ......CIII magnitude of tile d.....ementl, 88 weD • the deserlptive terms appHed.
The descriptive terms used in the interpretation of pulmonary function test results can be important since the conclusions drawn from the studies not only may influence decisions about a patient's em-
The responses were analyzed by comparing the interpretation from each physician to every other interpretation for the same patient. Each comparison was graded as either agreeing with another comparison or as differing by one (mild to moderate) or two categories (mild to severe). All ten patients under consideration had spirometric tests, and since there were 13 pulmonary physicians from each group who returned their questionnaires, there were 78 possible comparisons for each patient or 780 total comparisons for obstructive disease. For restrictive lung disease, only the five patients who had tests of total lung capacity measured were considered, so that there were 390 total comparisons available for restrictive disease in each physician-group.
For editorial comment, see page 377
ployability and insurability, but also color the attitude of the referring physician toward his patient. We recognized that there was a good deal of disagreement present in the narrative interpretation of similar data from pulmonary function tests by the physicians in our division, so we designed a study to assess the variability in interpretation of pulmonary function test results by respiratory disease physicians using their personal criteria for test interpretation. METHODS
We asked the members of the respiratory disease staff and fellows from the University of Washington (UW) and practicing chest physicians in the state of Washington to interpret ten consecutive pulmonary function tests (PFT ) from one laboratory. The tests were sequential and not selected to demonstrate specific points or to include diJlicult problems. Only the age, height, weight, predicted flow rates and lung volumes and the physiologic data from each patient were given to the interpreting physicians. The physicians were not biased by more detailed clinical information, physical examinations, or presumptive diagnosis. The interpretations were standardized by asking the physicians to identify and grade the severity of any obsbuctive or restrictive lung disease by checking the appropriate boxes titled: none present, mild, moderate or severe disease. ·From the Division of Respiratory Diseases US Public Health Service Hospital, ana the Division 01 Respiratory Diseases, University of Washington, Seattle. Presented at the 43rd Annual Scientific Assembly, American College of Chest Physicians, Las Vegas, October 30November 3, 1977. oOSenior FeJlow. t Assistant Professor. tPulmonary Technician. Manuscript received November 6; revision accepted December 19. Reprint requests: Dr. Huseby, USPHS Hospital, Seattle 98114
CHEST, 76: 4, OCTOBER, 1979
RESULTS
Table 1 summarizes the results of the study. There was a striking frequency of disagreement in the interpretation of the pulmonary function tests. The magnitude of the disagreements was no different whether the physicians had considerable interaction as in the university group, or practiced independently, as in the statewide group. DISCUSSION
A review of the published oriteria'" for the interpretation of obstructive and restrictive lung disease
Obstructive Disease Total Compared Agree Differ X 1 Differ X 2
Restrictive Disease Total Compared Agree
Differ X 1 Differ X 2
University of Washington
State of Washington
780 57% 41%
780 60% 37%
2%
390 63% 32% 5%
3% 300
65% 32%
3%
INTERPRETATION OF PULMONARY FUNCTION TESTS 389
Gaensler 1966
ACCP 1967
Ellis· 1975
Table 3-R.'ricIiH Di.ea.e Ca'e«orie. U.in. To'al Lan. Capaci',.
Utah 1975
80
o
70 FEV,/VC
NORMAL
•
MILO
~
MODERATE
B SEVERE
60
* FOR A PREO F[V,/VC .80~
50
40 FIGURE 1. Variation in obstmctive disease categories using FEV1/VC ratios. 1 - 4
provides insight into the results of the study. Figure 1 summarizes the suggested categories of obstructive disease from four sources. l-4 The criteria of Ellis and colleagues' were presented as percentages of the predicted FEVlIve ratio and for the purposes of this comparison we selected a predicted FEV 1/ VC ratio of 80 percent. In the range of FEVI/VC ratios from 80 percent to 40 percent there is complete agreement only for two narrow bands (67-69 percent, 52-59 percent). Thus, it is not surprising that a large number of the responses in our survey differed by one category. The available criteria for grading restrictive lung disease show similar disagreements. Table 2 shows the suggested levels for describing resbictive disease based on vital capacity and Table 3 gives similar infonnation when total lung capacity is known. In reviewing the responses to this study as well as our own experience, three problems were noted to cause disagreements: 1.- FEVI/VC vs FEVI. We have reviewed four criteria for obstruction based on FEVI/VC which are useful for excluding the effect of variation in VC, but with advanced disease, the functional impairment may correlate better with FEVI than the ratio (eg FEVI/VC of 1.012.0 = 50 percent vs 1.2/3.6 = 33 percent). 2. Combined abnormalities. It is quite possible, Table
2-R~'ricd"e
DiNaae Cale«orie. U.in .. J'i'a' Capaci',. Gaensler and Wright t
Ellis and Colleagues,
Normal
>79%
>79%
Mild
60%-79%
640/0-79 %
Moderate
500/0-59%
440/0-63%
Severe
Pred
390 CARY ET AL
Kanner and Morris,
Ellis and Colleagues, Normal
TLC>79%
TLC>81%
Mild
TLC 640/0-79% + VC >63%
TLC 66%-81 %
Moderate TLC 44%-79%+VC >44%-63% TLC 51%-65% Severe
TLC
