Symposium
Field Issues for the Plan and Operation of the Laboratory Component of the Third National Health and | Nutrition Examination Survey12 GERALDINE M. McQÅ’LLAN,*
ELAINE W. GUNTERï AND LINDA LANNOMï
*Diuision of Health Examination Statistics, National Center for Health Statistics, Centers for Disease Control, Hyattsuille, MD 20782, tD/w's/on of Enuironmental Health Laboratory Sciences, Center for Enuironmental Health and Injury Control, Centers for Disease Control, Atlanta, GA 30333, and Westat, Inc. of surveys and will be conducted between 1988 and 1994(1). The design of the NHANES III field laboratory and the laboratory protocol are based on several criteria that will be addressed in this paper: scientific merit, public health importance, practical utility, and feasi bility. Before we address these issues, a general description of the laboratory component of NHANES will be useful.
ABSTRACT The design of the laboratory component of a mobile examination survey such as the National Health and Nutrition Examination Survey requires that the physical limitation of the mobile examination center be balanced against the requirements of the laboratory analyses needed to fulfill the goals of the survey. In order to include an analysis in the survey, the scientific merit of the laboratory test must be established and a consensus must be reached on the appropriateness of the technology for the six years of the survey. The public health importance of the analysis and the sub sequent results are also evaluated before inclusion into the laboratory protocol. Finally, the feasibility of in corporating the analysis into the protocol is reviewed. The laboratory component of NHANES HIis discussed, addressing these points with descriptions of the reasons for inclusion and exclusion of key analytes. J. Hutr. 120:1446-1450, 1990.
CONTENT OF THE LABORATORY COMPONENT In each successive HANES survey, the number of laboratory analyses performed has increased steadily. Table 1 lists the analytes measured in NHANES I
INDEXING KEY WORDS:
•mobile examination survey •key analytes • method selection •sample handling •quality control
1 Presented as part of a conference, "Nutrition Monitoring and Nutrition Status Assessment", at the first fall meeting of the Amer ican Institute of Nutrition, Charleston, South Carolina, December 8-10, 1989. The conference was supported in part by cooperative agreement HPU880004-02-1 with the DHHS Office of Disease Pre vention and Health Promotion, the USDA Human Nutrition In formation Service, the DHHS National Center for Health Statistics, and the International Life Sciences Institute-Nutrition Foundation. 2 The Planning Committee for the meeting consisted of Drs.
Since 1960, the National Center for Health Statistics (NCHS) has been responsible for producing vital and health statistics for the United States. One of the major programs of the NCHS is the Third National Health and Nutrition Examination Survey (NHANES III). In the NHANES, individuals are randomly selected from households, interviewed, and invited to participate in medical examinations in the NCHS mobile examina tion centers (MEC). The most recent of the national surveys was conducted between 1976 and 1980 (NHANES II), and a special survey of the Hispanic population was conducted between 1982 and 1984 (HHANES). The NHANES III is the latest in this series 0022-3166/90
S3.00 ©1990 American Institute of Nutrition.
Helen A. Guthrie, Roy J. Martin, Linda D. Meyers, James A. Olson, Catherine E. Woteki, and Richard G. Allison (ex officio). The sym posium papers were edited by a committee consisting of Dr. James Allen Olson (coordinator), Dept. of Biochemistry & Biophysics, Iowa State University, Ames, IA; Dr. Cathy C. Campbell, Division of Nutritional Sciences, Cornell University, Ithaca, NY; Dr. Roy J. Martin, Dept. of Foods &. Nutrition, University of Georgia, Athens, GA¡and Dr. Catherine E. Woteki, Food & Nutrition Board, National Academy of Sciences, Washington, DC. Use of trade names is for identification only and does not con stitute endorsement by the Public Health Service or the U. S. De partment of Health and Human Services.
Received 10 December 1989. Accepted 11 July 1990.
1446 Downloaded from https://academic.oup.com/jn/article-abstract/120/suppl_11/1446/4738613 by Queen Mary University of London user on 24 August 2018
FIELD LABORATORY
OPERATION
(1971-1975), NHANES II (1976-1980), Hispanic HANES (1982-1984), and NHANES III (1988-1994). The ever-increasing number of analytes has placed an increasing burden on the MEC laboratory for pro cessing the blood and urine specimens. The increased number of outside laboratories performing analyses also has had an impact on the time it takes to ship the specimens. The MEC is designed to handle 10 sample persons (SPs) per half-day session. There are two sessions per day, either in the morning, running between 0830 and 1200; afternoon, between 1330 and 1700; or evening, between 1830 and 2200. Two mobile examination teams are in the field at one time. Each laboratory on the MEC is staffed by four certified medical technicians who are experienced in venipuncture, hematology, and serology. The med ical technicians rotate among four work stations in the MEC. Each work station has specific tasks asso ciated with it, which can be briefly listed as follows: 1. Venipuncture and Glucose Tolerance Test (GTT) 2. Specimen centrifugation, blood specimen pro cessing 3. Hematology, urine processing, and pregnancy testing 4. Processing, shipping, labeling blood and urine vials, and assisting other technicians as needed. Venipuncture (which includes administering a brief automated screening questionnaire about safety issues such as hemophilia and recent chemotherapy and fast ing questions) takes an average of 10 minutes per SP. Approximately 96 mL of blood are obtained from each adult sample person, with an additional 20 mL from volunteers for a Priority Toxicants Reference Range Study. A two-hour GTT is given to individuals who are not insulin-dependent diabetics and are 40-74 years of age. The technician who centrifuges and processes the blood must separate whole blood, serum, or plasma into 32 separate vials. Twenty-two of these specimens are sent to the central NHANES Laboratory at the Center for Environmental Health and Injury Control (CEHIC), Centers for Disease Control, in Atlanta. The rest of the specimens are shipped to contract labora tories. The technician who is responsible for the hematol ogy profile uses a Coulter Model S-Plus Jr. This model of the Coulter Counter provides 18 hématologiepa rameters. The calibration of the machine is verified each morning using Coulter's "S-Cal" Calibrator. The purposes of this calibration are to monitor the accuracy of the Coulter S-Plus Jr. and to correct for the variation in the results produced by the different instruments in each of the MECs over a six-year period. Results of the daily calibration with "S-Cal" are transmitted via phone lines from the instruments to Coulter head quarters and are compared to results obtained by Coulter Electronics. The results from each Coulter Downloaded from https://academic.oup.com/jn/article-abstract/120/suppl_11/1446/4738613 by Queen Mary University of London user on 24 August 2018
IN NHANES
1447
III
S-Plus Jr. must be within specified limits before the laboratory may run the day's specimens. A manual hematocrit is run once during each session as a verifi cation of the hematocrit results obtained with the SPlus Jr. The same technician also performs a pregnancy test on all females ages 20 to 59 years. This test is done prior to the X-rays and bone density testing to ensure that only women with a negative test result undergo these procedures. One 40-mL urine specimen is collected from every individual over the age of 6 yr. An additional urine specimen of 30 mL may be collected from adults aged 40-74 who volunteer to participate in the Priority Toxicant Study. The urine is aliquoted into five, 15mL polystyrene tubes for subsequent shipment and analysis by either CDC or a contract laboratory. The fourth laboratory technician labels all the vials and shippers, prepares the shipping transmitÃ-ais,packs the shippers, and assists the other technicians as needed (2).
SCIENTIFIC
MERIT
The primary consideration when deciding whether to include an assay into the laboratory component is the impact that data will have on the overall goals of the NHANES III survey. The NHANES III survey's overall purpose and goals are to estimate national prevalence of selected diseases, to provide national population reference distributions, to document and investigate secular trends, to con tribute to an understanding of disease etiology, and to investigate the natural history of selected diseases. The laboratory analyses that are performed in the MEC, CEHIC, and the contract laboratories are de signed to provide data that address the survey's goals and supplement the information obtained from the other components of the survey. A major emphasis of NHANES III is the collection of information related to the 13 diseases and condi tions listed in Table 2. The laboratory protocol is de signed to address research questions related to these topics. The Survey Planning and Development Branch of NCHS designed the laboratory and other compo nents of the survey after evaluating project proposals submitted by other government agencies, outside in terest groups, academicians, and other similar groups. Topic areas that were felt to have scientific merit were tested during three pilot studies before inclusion in NHANES III. Inclusion of an assay in the laboratory component underwent the same testing to which all components were subject. An assay must be accepted by the scientific community as "state-of-the-art" to be included in the protocol. Reference laboratories and experts in the relevant disciplines are polled to deter-
MCQUILLAN ETAL.
1448
TABLE 1 Laboratory
I. Hematological assessments a. Sedimentation rate b. Differential smears c. Hematocrit d. Hemoglobin e. Cell counts f. Neutrophil hypersegmentation g. Mean cell volume h. Red cell distribution width II. Serum biochemical assessments a. Folie acid b. Iron and total iron-binding capacity c. Vitamin C d. Vitamin D (25-hydroxy D) e. Zinc and copper f. Vitamin A g. Vitamin B-12 h. Plasma glucose (Gil) i. Selenium j. Cholesterol, total k. HDL and LDL cholesterol 1. Triglycérides m. Apolipoproteins Al and B n. Total and ionized calcium o. Ferritin p. Biochemistry profile: 1. Total carbon dioxide 2. Blood urea nitrogen 3. Total bilirubin 5. Alkaline phosphatase 6. Cholesterol 7. SCOT, AST 8. SGPT, ALT 9. LDH 10. Total protein 11. Albumin 12. Creatinine 13. Glucose 14. Calcium 15. Chloride 16. Uric acid 17. Phosphorus 18. Sodium 19. Potassium
analyses in NHANESI, U, m, and HHANES
I
II
H
III
x x x x x
x x x x
x x x x
x
x
x
x x x x x x x
x x
x x x
x x
x x x x
x
x
x
x
x
x x x x x
x x x
x x x x x x x
x x x
x
x
x x x x x x x x
x x x x x x x x x x x x x x x x x x
x x x x x x x x x x x x x x x x x x
x x x
x x
x x x x
mine which assay is acceptable or currently considered controversial. We strive to use the most recent tech nology in our laboratory assays since the assay must be performed unchanged for six years; however, de veloping methodology that is too new to be accepted by scientific experts is of little use in fulfilling the sur vey's goals. This often poses a dilemma for the NCHS staff, since laboratory methodologies are evolving rapidly. PUBLIC HEALTH IMPORTANCE Besides the scientific merit of each analysis, the public health importance of the data is also considered Downloaded from https://academic.oup.com/jn/article-abstract/120/suppl_11/1446/4738613 by Queen Mary University of London user on 24 August 2018
I q. Carotene profile r. Cotinine s. Bile salts t. Pesticides u. Syphilis serology v. Hepatitis A and B serology w. Tetanus x. Diphtheria, rubella, polio y. Herpes simplex I and II z. IgE aa. Human immunodeficiency virus bb. C-reactive protein cc. Rheumatoid factor dd. Follicle stimulating hormone ee. Luteinizing hormone ff. Thyroxine (T4) gg. Thyroid stimulating hormone (TSH) hh. Antithyroglobulin antibodies ii. Antimicrosomal antibodies jj. Insulin kk. C-peptide 11. Plasma fibrinogen III. Whole blood biochemistry assessments a. Protoporphyrin b. Lead c. Folate d. Carboxyhemoglobin e. Glycosylated hemoglobin f. Priority toxicant volatiles IV. Urinary assessments a. Urinalysis b. Pesticides c. Riboflavin
II
H
III x x
x
x x x x
x x
x x x x
x
x x x x x x x x x K E i E E
x
x x x x
x
x x
x x
x x x x x
x x x x x
x x
x
d. Thiamin e. Cadmium
x Ã
f. Creatinine g. Microalbumin h. Urinary iodine i. Pregnancy test j. Priority toxicant phenols V. Excess and reserve vials a. Serum b. White blood cells for DNA banking
x
x
x
x
x
x
x
x x
before an analysis is added to the laboratory compo nent. Besides supporting the research questions per taining to the target diseases, each analysis must also have an impact on current health questions that are TABLE 2 Target diseases and conditions Cardiovascular disease Chronic obstructive pulmonary Diabetes Gallbladder disease Osteoporosis Arthritis Kidney disease
disease
Infectious disease Dental disease Allergy Cancer Mental illness Hearing impairment
FIELD LABORATORY
OPERATION
being addressed by the Public Health Service. The public health importance of an analysis is assessed by NCHS staff and their consultants. When an analysis is accepted for its scientific merit and public health importance, two additional criteria must be satisfied to include the assay into the labo ratory: practical utility and feasibility.
PRACTICAL UTILITY AND FEASIBILITY Many worthwhile projects were proposed and tested during the pilot phase of NHANES III. The field test ing is the final test before the design of the survey is finalized. Several analyses were initially included in the testing phase of the survey and were excluded be cause of practicality issues. A Kodak model DT-60 dry chemical analyzer, which requires only 10 uL of sample per test, was initially included in the survey as part of the MEC laboratory protocol, primarily to provide lipid analysis for chil dren under the age of four years (the large volume of serum needed for the lipid analysis at our reference laboratory precludes doing this test on children from 1 to 3 years). Difficulties with the two-slide creatinine method, along with space and storage problems, were serious enough to warrant dropping the analysis from the survey. Urinalysis has always been included in the MEC laboratory procedure. Though not a complicated pro cedure, this test must be done in a timely fashion, and the equipment and reagents required valuable space in the laboratory. The data from this analysis have never been used, because a single analysis from a ran dom urine is considered too variable to address re search questions; therefore, this procedure was dropped. Zeta Sedimentation Ratios (ZSR) were included in the Washington, DC, pilot study using the Coulter Zetafuge. ZSR is a modification for the determination of the erythrocyte sedimentation rate (ESR) (3). Al though the ZSR theoretically has several advantages over the ESR, such as decreased performance time, amount of specimen used, and resistance to vibration error, we found the equipment problems to be severe. We could not get the Zetafuge to perform reliably in our mobile laboratory. It also required too much tech nician time; therefore, it was dropped from the survey. Originally, a multielement trace metal analysis was proposed for the survey. The blood tube and our col lection apparatus were not sufficiently free of back ground trace metal contamination to provide adequate detection for certain metals such as chromium and nickel in the blood of our SPs. The National Institute of Standards and Technology suggested that we obtain a blood specimen by having blood drip into a teflonlined vial from an open cannula. Obviously, this tech Downloaded from https://academic.oup.com/jn/article-abstract/120/suppl_11/1446/4738613 by Queen Mary University of London user on 24 August 2018
IN NHANES
III
1449
nique was considered impractical for a field survey. One of the interests of the survey is the banking of serum specimens for future uses. We were especially interested in collecting white blood cells for a DNA bank. When this proposal was initially introduced, the technology that existed required that the white cells be separated in the MEC and immediately be frozen at -70°C.This procedure would have required a liquid nitrogen tank in the MEC. The mobile nature of the trailers and the space limitations did not allow us to incorporate this procedure into the survey. After the pilot and pretest, the Genetics Branch of CEHIC in formed us that with the development of polymerase chain reaction (PCR) and new culturing techniques, blood could now be collected and shipped refrigerated before the separation of white blood cells. Because of the public health importance of such a DNA bank and the increase in feasibility with the new scientific tech niques, this assay was incorporated into the survey.
CONCLUSION In summary, the inclusion of any procedure into the NHANES III laboratory is a complicated process that must undergo not only rigorous scientific discus sion but must also fit into the practical day-to-day, high-volume schedule of a mobile field laboratory. In spite of these limitations, criteria can be designed to help determine whether an assay will fit into the survey. The first criterion that must be met in order for an assay to be included in the survey is scientific merit. As described previously, the assay must represent "state-of-the-art" technology that is accepted by the scientific community. If an assay meets this criterion, its public health importance is assessed in the context of the goals of the survey. If an assay is thought to contribute to the goals of the survey and the data pro duced will contribute significantly to public health, the feasibility within the context of the MEC will then be addressed. If an analytic instrument is being con sidered for inclusion into the MEC equipment, the machine must provide accurate and precise results and at the same time be rugged enough for constant travel and performance under less-than-ideal conditions. Constant recalibration of instruments requires tech nician time and also reduces the validity of the results. The machine should also provide some mechanism for between-site comparability. Any instrument included in the survey must be state-of-the-art and at the same time provide some assurance of longevity. Any pro cedure conducted in the MEC must have adequate throughput. This means that although an assay may be acceptable by all other criteria, it cannot require too much of either the technician's or the SP's time, therefore jeopardizing the other components of the
1450
MCQUILLAN ETAL.
survey. For assays that are performed in the CDC or contract laboratories, the ability of a machine to with stand travel is not a factor, but the other criteria do hold. The procedure must be followed for six years; therefore, the procedures must be state-of-the-art at the beginning of the survey through the sixth year. If the throughput is too slow, the expense of the assay will outweigh the value of the results. LITERATURE CITED 1. NATIONAL CENTER FOR HEALTH STATISTICS.(1988) Final Clearance Package for Approval by the Office of Management
Downloaded from https://academic.oup.com/jn/article-abstract/120/suppl_11/1446/4738613 by Queen Mary University of London user on 24 August 2018
and Budget for the Third National Health and Nutrition Ex amination Survey (NHANES III). National Center for Health Statistics, Centers for Disease Control, Public Health Service, U. S. Department of Health and Human Services, Hyattsville, MD. 2. NATIONALHEALTHANDNUTRITIONEXAMINATION SURVEY III: Manual for Medical Technicians. (1988) Westat, Inc. Rockville, MD. 3. MORRISM. W., FINALS,R. S. & NELSON,D. A. (1977) The zeta sedimentation ratio (ZSR)and activity of disease in rheumatoid arthritis. Am. /. Clin. Pathol. 68: 760-762.
Field Issues for the Plan and Operation of the Laboratory Component of the Third National Health and | Nutrition Examination Survey12 GERALDINE M. McQÅ’LLAN,*
ELAINE W. GUNTERï AND LINDA LANNOMï
*Diuision of Health Examination Statistics, National Center for Health Statistics, Centers for Disease Control, Hyattsuille, MD 20782, tD/w's/on of Enuironmental Health Laboratory Sciences, Center for Enuironmental Health and Injury Control, Centers for Disease Control, Atlanta, GA 30333, and Westat, Inc. of surveys and will be conducted between 1988 and 1994(1). The design of the NHANES III field laboratory and the laboratory protocol are based on several criteria that will be addressed in this paper: scientific merit, public health importance, practical utility, and feasi bility. Before we address these issues, a general description of the laboratory component of NHANES will be useful.
ABSTRACT The design of the laboratory component of a mobile examination survey such as the National Health and Nutrition Examination Survey requires that the physical limitation of the mobile examination center be balanced against the requirements of the laboratory analyses needed to fulfill the goals of the survey. In order to include an analysis in the survey, the scientific merit of the laboratory test must be established and a consensus must be reached on the appropriateness of the technology for the six years of the survey. The public health importance of the analysis and the sub sequent results are also evaluated before inclusion into the laboratory protocol. Finally, the feasibility of in corporating the analysis into the protocol is reviewed. The laboratory component of NHANES HIis discussed, addressing these points with descriptions of the reasons for inclusion and exclusion of key analytes. J. Hutr. 120:1446-1450, 1990.
CONTENT OF THE LABORATORY COMPONENT In each successive HANES survey, the number of laboratory analyses performed has increased steadily. Table 1 lists the analytes measured in NHANES I
INDEXING KEY WORDS:
•mobile examination survey •key analytes • method selection •sample handling •quality control
1 Presented as part of a conference, "Nutrition Monitoring and Nutrition Status Assessment", at the first fall meeting of the Amer ican Institute of Nutrition, Charleston, South Carolina, December 8-10, 1989. The conference was supported in part by cooperative agreement HPU880004-02-1 with the DHHS Office of Disease Pre vention and Health Promotion, the USDA Human Nutrition In formation Service, the DHHS National Center for Health Statistics, and the International Life Sciences Institute-Nutrition Foundation. 2 The Planning Committee for the meeting consisted of Drs.
Since 1960, the National Center for Health Statistics (NCHS) has been responsible for producing vital and health statistics for the United States. One of the major programs of the NCHS is the Third National Health and Nutrition Examination Survey (NHANES III). In the NHANES, individuals are randomly selected from households, interviewed, and invited to participate in medical examinations in the NCHS mobile examina tion centers (MEC). The most recent of the national surveys was conducted between 1976 and 1980 (NHANES II), and a special survey of the Hispanic population was conducted between 1982 and 1984 (HHANES). The NHANES III is the latest in this series 0022-3166/90
S3.00 ©1990 American Institute of Nutrition.
Helen A. Guthrie, Roy J. Martin, Linda D. Meyers, James A. Olson, Catherine E. Woteki, and Richard G. Allison (ex officio). The sym posium papers were edited by a committee consisting of Dr. James Allen Olson (coordinator), Dept. of Biochemistry & Biophysics, Iowa State University, Ames, IA; Dr. Cathy C. Campbell, Division of Nutritional Sciences, Cornell University, Ithaca, NY; Dr. Roy J. Martin, Dept. of Foods &. Nutrition, University of Georgia, Athens, GA¡and Dr. Catherine E. Woteki, Food & Nutrition Board, National Academy of Sciences, Washington, DC. Use of trade names is for identification only and does not con stitute endorsement by the Public Health Service or the U. S. De partment of Health and Human Services.
Received 10 December 1989. Accepted 11 July 1990.
1446 Downloaded from https://academic.oup.com/jn/article-abstract/120/suppl_11/1446/4738613 by Queen Mary University of London user on 24 August 2018
FIELD LABORATORY
OPERATION
(1971-1975), NHANES II (1976-1980), Hispanic HANES (1982-1984), and NHANES III (1988-1994). The ever-increasing number of analytes has placed an increasing burden on the MEC laboratory for pro cessing the blood and urine specimens. The increased number of outside laboratories performing analyses also has had an impact on the time it takes to ship the specimens. The MEC is designed to handle 10 sample persons (SPs) per half-day session. There are two sessions per day, either in the morning, running between 0830 and 1200; afternoon, between 1330 and 1700; or evening, between 1830 and 2200. Two mobile examination teams are in the field at one time. Each laboratory on the MEC is staffed by four certified medical technicians who are experienced in venipuncture, hematology, and serology. The med ical technicians rotate among four work stations in the MEC. Each work station has specific tasks asso ciated with it, which can be briefly listed as follows: 1. Venipuncture and Glucose Tolerance Test (GTT) 2. Specimen centrifugation, blood specimen pro cessing 3. Hematology, urine processing, and pregnancy testing 4. Processing, shipping, labeling blood and urine vials, and assisting other technicians as needed. Venipuncture (which includes administering a brief automated screening questionnaire about safety issues such as hemophilia and recent chemotherapy and fast ing questions) takes an average of 10 minutes per SP. Approximately 96 mL of blood are obtained from each adult sample person, with an additional 20 mL from volunteers for a Priority Toxicants Reference Range Study. A two-hour GTT is given to individuals who are not insulin-dependent diabetics and are 40-74 years of age. The technician who centrifuges and processes the blood must separate whole blood, serum, or plasma into 32 separate vials. Twenty-two of these specimens are sent to the central NHANES Laboratory at the Center for Environmental Health and Injury Control (CEHIC), Centers for Disease Control, in Atlanta. The rest of the specimens are shipped to contract labora tories. The technician who is responsible for the hematol ogy profile uses a Coulter Model S-Plus Jr. This model of the Coulter Counter provides 18 hématologiepa rameters. The calibration of the machine is verified each morning using Coulter's "S-Cal" Calibrator. The purposes of this calibration are to monitor the accuracy of the Coulter S-Plus Jr. and to correct for the variation in the results produced by the different instruments in each of the MECs over a six-year period. Results of the daily calibration with "S-Cal" are transmitted via phone lines from the instruments to Coulter head quarters and are compared to results obtained by Coulter Electronics. The results from each Coulter Downloaded from https://academic.oup.com/jn/article-abstract/120/suppl_11/1446/4738613 by Queen Mary University of London user on 24 August 2018
IN NHANES
1447
III
S-Plus Jr. must be within specified limits before the laboratory may run the day's specimens. A manual hematocrit is run once during each session as a verifi cation of the hematocrit results obtained with the SPlus Jr. The same technician also performs a pregnancy test on all females ages 20 to 59 years. This test is done prior to the X-rays and bone density testing to ensure that only women with a negative test result undergo these procedures. One 40-mL urine specimen is collected from every individual over the age of 6 yr. An additional urine specimen of 30 mL may be collected from adults aged 40-74 who volunteer to participate in the Priority Toxicant Study. The urine is aliquoted into five, 15mL polystyrene tubes for subsequent shipment and analysis by either CDC or a contract laboratory. The fourth laboratory technician labels all the vials and shippers, prepares the shipping transmitÃ-ais,packs the shippers, and assists the other technicians as needed (2).
SCIENTIFIC
MERIT
The primary consideration when deciding whether to include an assay into the laboratory component is the impact that data will have on the overall goals of the NHANES III survey. The NHANES III survey's overall purpose and goals are to estimate national prevalence of selected diseases, to provide national population reference distributions, to document and investigate secular trends, to con tribute to an understanding of disease etiology, and to investigate the natural history of selected diseases. The laboratory analyses that are performed in the MEC, CEHIC, and the contract laboratories are de signed to provide data that address the survey's goals and supplement the information obtained from the other components of the survey. A major emphasis of NHANES III is the collection of information related to the 13 diseases and condi tions listed in Table 2. The laboratory protocol is de signed to address research questions related to these topics. The Survey Planning and Development Branch of NCHS designed the laboratory and other compo nents of the survey after evaluating project proposals submitted by other government agencies, outside in terest groups, academicians, and other similar groups. Topic areas that were felt to have scientific merit were tested during three pilot studies before inclusion in NHANES III. Inclusion of an assay in the laboratory component underwent the same testing to which all components were subject. An assay must be accepted by the scientific community as "state-of-the-art" to be included in the protocol. Reference laboratories and experts in the relevant disciplines are polled to deter-
MCQUILLAN ETAL.
1448
TABLE 1 Laboratory
I. Hematological assessments a. Sedimentation rate b. Differential smears c. Hematocrit d. Hemoglobin e. Cell counts f. Neutrophil hypersegmentation g. Mean cell volume h. Red cell distribution width II. Serum biochemical assessments a. Folie acid b. Iron and total iron-binding capacity c. Vitamin C d. Vitamin D (25-hydroxy D) e. Zinc and copper f. Vitamin A g. Vitamin B-12 h. Plasma glucose (Gil) i. Selenium j. Cholesterol, total k. HDL and LDL cholesterol 1. Triglycérides m. Apolipoproteins Al and B n. Total and ionized calcium o. Ferritin p. Biochemistry profile: 1. Total carbon dioxide 2. Blood urea nitrogen 3. Total bilirubin 5. Alkaline phosphatase 6. Cholesterol 7. SCOT, AST 8. SGPT, ALT 9. LDH 10. Total protein 11. Albumin 12. Creatinine 13. Glucose 14. Calcium 15. Chloride 16. Uric acid 17. Phosphorus 18. Sodium 19. Potassium
analyses in NHANESI, U, m, and HHANES
I
II
H
III
x x x x x
x x x x
x x x x
x
x
x
x x x x x x x
x x
x x x
x x
x x x x
x
x
x
x
x
x x x x x
x x x
x x x x x x x
x x x
x
x
x x x x x x x x
x x x x x x x x x x x x x x x x x x
x x x x x x x x x x x x x x x x x x
x x x
x x
x x x x
mine which assay is acceptable or currently considered controversial. We strive to use the most recent tech nology in our laboratory assays since the assay must be performed unchanged for six years; however, de veloping methodology that is too new to be accepted by scientific experts is of little use in fulfilling the sur vey's goals. This often poses a dilemma for the NCHS staff, since laboratory methodologies are evolving rapidly. PUBLIC HEALTH IMPORTANCE Besides the scientific merit of each analysis, the public health importance of the data is also considered Downloaded from https://academic.oup.com/jn/article-abstract/120/suppl_11/1446/4738613 by Queen Mary University of London user on 24 August 2018
I q. Carotene profile r. Cotinine s. Bile salts t. Pesticides u. Syphilis serology v. Hepatitis A and B serology w. Tetanus x. Diphtheria, rubella, polio y. Herpes simplex I and II z. IgE aa. Human immunodeficiency virus bb. C-reactive protein cc. Rheumatoid factor dd. Follicle stimulating hormone ee. Luteinizing hormone ff. Thyroxine (T4) gg. Thyroid stimulating hormone (TSH) hh. Antithyroglobulin antibodies ii. Antimicrosomal antibodies jj. Insulin kk. C-peptide 11. Plasma fibrinogen III. Whole blood biochemistry assessments a. Protoporphyrin b. Lead c. Folate d. Carboxyhemoglobin e. Glycosylated hemoglobin f. Priority toxicant volatiles IV. Urinary assessments a. Urinalysis b. Pesticides c. Riboflavin
II
H
III x x
x
x x x x
x x
x x x x
x
x x x x x x x x x K E i E E
x
x x x x
x
x x
x x
x x x x x
x x x x x
x x
x
d. Thiamin e. Cadmium
x Ã
f. Creatinine g. Microalbumin h. Urinary iodine i. Pregnancy test j. Priority toxicant phenols V. Excess and reserve vials a. Serum b. White blood cells for DNA banking
x
x
x
x
x
x
x
x x
before an analysis is added to the laboratory compo nent. Besides supporting the research questions per taining to the target diseases, each analysis must also have an impact on current health questions that are TABLE 2 Target diseases and conditions Cardiovascular disease Chronic obstructive pulmonary Diabetes Gallbladder disease Osteoporosis Arthritis Kidney disease
disease
Infectious disease Dental disease Allergy Cancer Mental illness Hearing impairment
FIELD LABORATORY
OPERATION
being addressed by the Public Health Service. The public health importance of an analysis is assessed by NCHS staff and their consultants. When an analysis is accepted for its scientific merit and public health importance, two additional criteria must be satisfied to include the assay into the labo ratory: practical utility and feasibility.
PRACTICAL UTILITY AND FEASIBILITY Many worthwhile projects were proposed and tested during the pilot phase of NHANES III. The field test ing is the final test before the design of the survey is finalized. Several analyses were initially included in the testing phase of the survey and were excluded be cause of practicality issues. A Kodak model DT-60 dry chemical analyzer, which requires only 10 uL of sample per test, was initially included in the survey as part of the MEC laboratory protocol, primarily to provide lipid analysis for chil dren under the age of four years (the large volume of serum needed for the lipid analysis at our reference laboratory precludes doing this test on children from 1 to 3 years). Difficulties with the two-slide creatinine method, along with space and storage problems, were serious enough to warrant dropping the analysis from the survey. Urinalysis has always been included in the MEC laboratory procedure. Though not a complicated pro cedure, this test must be done in a timely fashion, and the equipment and reagents required valuable space in the laboratory. The data from this analysis have never been used, because a single analysis from a ran dom urine is considered too variable to address re search questions; therefore, this procedure was dropped. Zeta Sedimentation Ratios (ZSR) were included in the Washington, DC, pilot study using the Coulter Zetafuge. ZSR is a modification for the determination of the erythrocyte sedimentation rate (ESR) (3). Al though the ZSR theoretically has several advantages over the ESR, such as decreased performance time, amount of specimen used, and resistance to vibration error, we found the equipment problems to be severe. We could not get the Zetafuge to perform reliably in our mobile laboratory. It also required too much tech nician time; therefore, it was dropped from the survey. Originally, a multielement trace metal analysis was proposed for the survey. The blood tube and our col lection apparatus were not sufficiently free of back ground trace metal contamination to provide adequate detection for certain metals such as chromium and nickel in the blood of our SPs. The National Institute of Standards and Technology suggested that we obtain a blood specimen by having blood drip into a teflonlined vial from an open cannula. Obviously, this tech Downloaded from https://academic.oup.com/jn/article-abstract/120/suppl_11/1446/4738613 by Queen Mary University of London user on 24 August 2018
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nique was considered impractical for a field survey. One of the interests of the survey is the banking of serum specimens for future uses. We were especially interested in collecting white blood cells for a DNA bank. When this proposal was initially introduced, the technology that existed required that the white cells be separated in the MEC and immediately be frozen at -70°C.This procedure would have required a liquid nitrogen tank in the MEC. The mobile nature of the trailers and the space limitations did not allow us to incorporate this procedure into the survey. After the pilot and pretest, the Genetics Branch of CEHIC in formed us that with the development of polymerase chain reaction (PCR) and new culturing techniques, blood could now be collected and shipped refrigerated before the separation of white blood cells. Because of the public health importance of such a DNA bank and the increase in feasibility with the new scientific tech niques, this assay was incorporated into the survey.
CONCLUSION In summary, the inclusion of any procedure into the NHANES III laboratory is a complicated process that must undergo not only rigorous scientific discus sion but must also fit into the practical day-to-day, high-volume schedule of a mobile field laboratory. In spite of these limitations, criteria can be designed to help determine whether an assay will fit into the survey. The first criterion that must be met in order for an assay to be included in the survey is scientific merit. As described previously, the assay must represent "state-of-the-art" technology that is accepted by the scientific community. If an assay meets this criterion, its public health importance is assessed in the context of the goals of the survey. If an assay is thought to contribute to the goals of the survey and the data pro duced will contribute significantly to public health, the feasibility within the context of the MEC will then be addressed. If an analytic instrument is being con sidered for inclusion into the MEC equipment, the machine must provide accurate and precise results and at the same time be rugged enough for constant travel and performance under less-than-ideal conditions. Constant recalibration of instruments requires tech nician time and also reduces the validity of the results. The machine should also provide some mechanism for between-site comparability. Any instrument included in the survey must be state-of-the-art and at the same time provide some assurance of longevity. Any pro cedure conducted in the MEC must have adequate throughput. This means that although an assay may be acceptable by all other criteria, it cannot require too much of either the technician's or the SP's time, therefore jeopardizing the other components of the
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survey. For assays that are performed in the CDC or contract laboratories, the ability of a machine to with stand travel is not a factor, but the other criteria do hold. The procedure must be followed for six years; therefore, the procedures must be state-of-the-art at the beginning of the survey through the sixth year. If the throughput is too slow, the expense of the assay will outweigh the value of the results. LITERATURE CITED 1. NATIONAL CENTER FOR HEALTH STATISTICS.(1988) Final Clearance Package for Approval by the Office of Management
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and Budget for the Third National Health and Nutrition Ex amination Survey (NHANES III). National Center for Health Statistics, Centers for Disease Control, Public Health Service, U. S. Department of Health and Human Services, Hyattsville, MD. 2. NATIONALHEALTHANDNUTRITIONEXAMINATION SURVEY III: Manual for Medical Technicians. (1988) Westat, Inc. Rockville, MD. 3. MORRISM. W., FINALS,R. S. & NELSON,D. A. (1977) The zeta sedimentation ratio (ZSR)and activity of disease in rheumatoid arthritis. Am. /. Clin. Pathol. 68: 760-762.
