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Disparities in Clinical Laboratory Performance for Blood Lead Analysis

Disparities in Clinical Laboratory Performance for Blood Lead Analysis Abstract Objective: To evaluate the validity of blood lead analysis for clinical specimens. Design: We submitted blood lead samples with a known lead concentration, in a blinded fashion, as clinical specimens to 18 laboratories. These laboratories were surveyed for the following characteristics that were hypothesized to be related to assay validity: laboratory ownership (state vs private), participation in the Centers for Disease Control Blood Lead Proficiency Program, assay method, and price. Each laboratory received 6 specimens with an actual blood lead (ABPb) concentration of 0.43 μmol/L (9 μg/dL) and 3 additional specimens—each with an ABPb concentration of 0.33, 0.89, and 1.59 μmol/L (6.9, 18.4, and 32.9 μg/dL, respectively). Outcome Measures: Misclassification error rates for reporting an elevation (≥0.48 μmol/L [≥10 μg/dL]) in the blood lead concentration, the within-laboratory mean and coefficient of variation (CV) (for multiple specimens with an ABPb concentration of 0.43 μmol/L [9 μg/dL]), and the adjusted odds of a reported blood lead concentration differing from those of an ABPb concentration by more than 0.14 μmol/L (3 μg/dL). Results: Blood lead results were obtained for 157 of 162 submissions. One laboratory reported all blood lead specimens as "below 0.48 μmol/L (10 μg/dL)." Two (11%) of 18 specimens with an ABPb concentration of 0.89 μmol/L (18.4 μg/dL) and 1 (6%) of 17 with an ABPb concentration of 1.59 μmol/L (32.9 μg/dL) were classified as below 0.48 μmol/L (10 μg/dL); 2 (11%) of 18 with an ABPb concentration of 0.33 μmol/L (6.9 μg/dL) and 44 (42%) of 104 with an ABPb concentration of 0.43 μmol/L (9 μg/dL) were classified as 0.48 μmol/L or greater (≥ 10 μg/dL). For specimens with an ABPb concentration of 0.43 μmol/L (9 μg/dL), the within-laboratory mean ranged from 0.23 to 0.52 μmol/L (4.8-10.7 μg/dL); the CV ranged from 3% to 37%. Laboratories that used anodic stripping voltammetry were 6.3 (95% confidence interval, 1.4-28.6) times more likely to report a specimen that differed from the ABPb concentration by more than 0.14 μmol/L (3 μg/dL) than those that used atomic absorption methods. No other laboratory characteristic predicted discordance between the reported blood lead and ABPb concentrations. Conclusions: This study documents wide variation in the validity of the blood lead measurement among clinical laboratories. While the performance of some laboratories far exceeded the criteria of the Centers for Disease Control Blood Lead Proficiency Program, others made large errors that could have resulted in the false-negative misclassification of children with significant lead exposure. Given these differences, the purchasers of laboratory services may require access to laboratory proficiency data to make rational choices among clinical laboratories. Further study of laboratory performance on clinical specimens is required to determine if order-of-magnitude errors occur with sufficient frequency to warrant routine submission of blinded quality control specimens by proficiency programs and to determine the cause of the poor performance of laboratories that used the anodic stripping voltammetry methodology.(Arch Pediatr Adolesc Med. 1996;150:609-614) References 1. Bellinger D. Prenatal/early postnatal exposure to lead and risk of developmental impairment . Birth Defects . 1989;25:73-97. 2. Bellinger D, Leviton A, Needleman HL, Waternaux C, Rabinowitz M. Low-level lead exposure and infant development in the first year . Neurobehav Toxicol Teratol . 1986;8:151-161. 3. Bellinger D, Sloman J, Leviton A, Rabinowitz M, Needleman HL, Waternaux C. Low-level lead exposure and children's cognitive function in the preschool years . Pediatrics . 1991;87:219-227. 4. Centers for Disease Control and Prevention. Blood Lead Proficiency Testing . Atlanta, Ga: US Dept of Health and Human Services, Public Health Service; 1994. 5. Sargent JD, Dalton M, Stukel TA, Roda S, Klein RZ. Evaluation of capillary collection methods for blood lead screening in children . Ambulatory Child Health . 1995;1:112-122. 6. Schlenker TL, Johnson C, Mark D, et al. Screening for pediatric lead poisoning: comparability of simultaneously drawn capillary and venous samples . JAMA . 1994;271:1346-1348.Crossref 7. Schonfeld DJ, Cullen MR, Rainey PM, et al. Screening for lead poisoning in an urban pediatric clinic using samples obtained by fingerstick . Pediatrics . 1994; 94:174-179. 8. Parsons PJ. Monitoring human exposure to lead: an assessment of current laboratory performance for the determination of blood lead . Environ Res . 1992; 57:149-162.Crossref 9. Subramanian KS. Determination of lead in blood—an interlaboratory study . Sci Total Environ . 1988;71:125-130.Crossref 10. Morisi G, Patriarca M, Taggi F. The interlaboratorial quality assurance program for blood lead determination: an evaluation of methods and results . Ann Ist Super Sanita . 1989;25:405-416. 11. Bullock DG, Smith NJ, Whitehead TP. External quality assessment of assays of lead in blood . Clin Chem . 1986;32:1884-1889. 12. Boone J, Hearn T, Lewis S. Comparison of interlaboratory results for blood lead with results from a definitive method . Clin Chem . 1979;25:389-393. 13. Centers for Disease Control. Preventing Lead Poisoning in Young Children: a Statement by the Centers for Disease Control . Atlanta, Ga: Centers for Disease Control; 1991. 14. Agency for Health Care Policy and Research. Clinical practice guidelines and cost analysis . In: Grady ML, Weis KA, eds. Cost Analysis Methodology for Clinical Practice Guidelines. Baltimore, Md: Agency for Health Care Policy and Research; 1995. No. 95-0001. 15. Johannesson M. The concept of cost in the economic evaluation of health care: a theoretical inquiry . Int J Technol Assess Health Care . 1994;10:675-682.Crossref 16. Robinson R. Costs and cost-minimisation analysis . BMJ . 1993;307:726-728.Crossref http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Pediatrics & Adolescent Medicine American Medical Association

Disparities in Clinical Laboratory Performance for Blood Lead Analysis

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References (16)

Publisher
American Medical Association
Copyright
Copyright © 1996 American Medical Association. All Rights Reserved.
ISSN
1072-4710
eISSN
1538-3628
DOI
10.1001/archpedi.1996.02170310043008
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Abstract

Abstract Objective: To evaluate the validity of blood lead analysis for clinical specimens. Design: We submitted blood lead samples with a known lead concentration, in a blinded fashion, as clinical specimens to 18 laboratories. These laboratories were surveyed for the following characteristics that were hypothesized to be related to assay validity: laboratory ownership (state vs private), participation in the Centers for Disease Control Blood Lead Proficiency Program, assay method, and price. Each laboratory received 6 specimens with an actual blood lead (ABPb) concentration of 0.43 μmol/L (9 μg/dL) and 3 additional specimens—each with an ABPb concentration of 0.33, 0.89, and 1.59 μmol/L (6.9, 18.4, and 32.9 μg/dL, respectively). Outcome Measures: Misclassification error rates for reporting an elevation (≥0.48 μmol/L [≥10 μg/dL]) in the blood lead concentration, the within-laboratory mean and coefficient of variation (CV) (for multiple specimens with an ABPb concentration of 0.43 μmol/L [9 μg/dL]), and the adjusted odds of a reported blood lead concentration differing from those of an ABPb concentration by more than 0.14 μmol/L (3 μg/dL). Results: Blood lead results were obtained for 157 of 162 submissions. One laboratory reported all blood lead specimens as "below 0.48 μmol/L (10 μg/dL)." Two (11%) of 18 specimens with an ABPb concentration of 0.89 μmol/L (18.4 μg/dL) and 1 (6%) of 17 with an ABPb concentration of 1.59 μmol/L (32.9 μg/dL) were classified as below 0.48 μmol/L (10 μg/dL); 2 (11%) of 18 with an ABPb concentration of 0.33 μmol/L (6.9 μg/dL) and 44 (42%) of 104 with an ABPb concentration of 0.43 μmol/L (9 μg/dL) were classified as 0.48 μmol/L or greater (≥ 10 μg/dL). For specimens with an ABPb concentration of 0.43 μmol/L (9 μg/dL), the within-laboratory mean ranged from 0.23 to 0.52 μmol/L (4.8-10.7 μg/dL); the CV ranged from 3% to 37%. Laboratories that used anodic stripping voltammetry were 6.3 (95% confidence interval, 1.4-28.6) times more likely to report a specimen that differed from the ABPb concentration by more than 0.14 μmol/L (3 μg/dL) than those that used atomic absorption methods. No other laboratory characteristic predicted discordance between the reported blood lead and ABPb concentrations. Conclusions: This study documents wide variation in the validity of the blood lead measurement among clinical laboratories. While the performance of some laboratories far exceeded the criteria of the Centers for Disease Control Blood Lead Proficiency Program, others made large errors that could have resulted in the false-negative misclassification of children with significant lead exposure. Given these differences, the purchasers of laboratory services may require access to laboratory proficiency data to make rational choices among clinical laboratories. Further study of laboratory performance on clinical specimens is required to determine if order-of-magnitude errors occur with sufficient frequency to warrant routine submission of blinded quality control specimens by proficiency programs and to determine the cause of the poor performance of laboratories that used the anodic stripping voltammetry methodology.(Arch Pediatr Adolesc Med. 1996;150:609-614) References 1. Bellinger D. Prenatal/early postnatal exposure to lead and risk of developmental impairment . Birth Defects . 1989;25:73-97. 2. Bellinger D, Leviton A, Needleman HL, Waternaux C, Rabinowitz M. Low-level lead exposure and infant development in the first year . Neurobehav Toxicol Teratol . 1986;8:151-161. 3. Bellinger D, Sloman J, Leviton A, Rabinowitz M, Needleman HL, Waternaux C. Low-level lead exposure and children's cognitive function in the preschool years . Pediatrics . 1991;87:219-227. 4. Centers for Disease Control and Prevention. Blood Lead Proficiency Testing . Atlanta, Ga: US Dept of Health and Human Services, Public Health Service; 1994. 5. Sargent JD, Dalton M, Stukel TA, Roda S, Klein RZ. Evaluation of capillary collection methods for blood lead screening in children . Ambulatory Child Health . 1995;1:112-122. 6. Schlenker TL, Johnson C, Mark D, et al. Screening for pediatric lead poisoning: comparability of simultaneously drawn capillary and venous samples . JAMA . 1994;271:1346-1348.Crossref 7. Schonfeld DJ, Cullen MR, Rainey PM, et al. Screening for lead poisoning in an urban pediatric clinic using samples obtained by fingerstick . Pediatrics . 1994; 94:174-179. 8. Parsons PJ. Monitoring human exposure to lead: an assessment of current laboratory performance for the determination of blood lead . Environ Res . 1992; 57:149-162.Crossref 9. Subramanian KS. Determination of lead in blood—an interlaboratory study . Sci Total Environ . 1988;71:125-130.Crossref 10. Morisi G, Patriarca M, Taggi F. The interlaboratorial quality assurance program for blood lead determination: an evaluation of methods and results . Ann Ist Super Sanita . 1989;25:405-416. 11. Bullock DG, Smith NJ, Whitehead TP. External quality assessment of assays of lead in blood . Clin Chem . 1986;32:1884-1889. 12. Boone J, Hearn T, Lewis S. Comparison of interlaboratory results for blood lead with results from a definitive method . Clin Chem . 1979;25:389-393. 13. Centers for Disease Control. Preventing Lead Poisoning in Young Children: a Statement by the Centers for Disease Control . Atlanta, Ga: Centers for Disease Control; 1991. 14. Agency for Health Care Policy and Research. Clinical practice guidelines and cost analysis . In: Grady ML, Weis KA, eds. Cost Analysis Methodology for Clinical Practice Guidelines. Baltimore, Md: Agency for Health Care Policy and Research; 1995. No. 95-0001. 15. Johannesson M. The concept of cost in the economic evaluation of health care: a theoretical inquiry . Int J Technol Assess Health Care . 1994;10:675-682.Crossref 16. Robinson R. Costs and cost-minimisation analysis . BMJ . 1993;307:726-728.Crossref

Journal

Archives of Pediatrics & Adolescent Medicine – American Medical Association

Published: Jun 1, 1996

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