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Accuracy and Reproducibility of Blood Lead Testing in Commercial Laboratories
Nishith K. Jobanputra, MPH;
Robert Jones, PhD;
Gail Buckler, RN, COHN, MPH;
Ronald P. Cody, EdD;
Michael Gochfeld, MD, PhD;
Thomas M. Matte, MD, MPH;
David Q. Rich, BS;
George G. Rhoads, MD, MPH
Arch Pediatr Adolesc Med. 1998;152:548-553.
Objective To assess the proficiency of commercial laboratories in analyzing lead in clinical blood samples from subjects without overt lead exposure.
Design We submitted masked duplicate blood lead specimens to 8 masked laboratories. Each laboratory received blood aliquots immediately following drawing (time 1) and 2 weeks later (time 2) from 7 human subjects and 3 bovine blood samples with known lead levels of 0.26, 0.57, and 0.79 µmol/L (5.4, 11.8, and 16.4 µg/dL). Of the 8 laboratories, 5 were commercial laboratories, 1 was a state laboratory, 1 was a research laboratory, and 1 was the Centers for Disease Control and Prevention reference laboratory.
Outcome Measures Correlation coefficients were calculated, and differences within and between laboratories were assessed by analysis of variance.
Results Results were obtained for all specimens, with all the human subjects' overall mean lead levels being less than 0.48 µmol/L (<10 µg/dL). Each laboratory reported all human blood specimens appropriately, as having lead levels less than 0.48 µmol/L (<10 µg/dL) and within 0.14 µmol/L (3 µg/dL) of the overall mean for that subject. All internal reproducibilities were very high (range, 0.92-1.00) except for one (0.60), possibly lower because of 1 pair of specimens. Mean differences between blood samples analyzed at time 1 and time 2 ranged from -1.4 to 1.2, with only 2 laboratories having significant differences (P<.01).
Conclusions Overall, there was strong reproducibility within and among laboratories, with no overall time trend or interlaboratory or intralaboratory variance. The storage conditions did not seem to affect the aggregate results. The data suggest that through implementation of the Centers for Disease Control and Prevention/Wisconsin Blood Lead Proficiency Testing Program, the Centers for Disease Control and Prevention's Blood Lead Laboratory Reference System, and mandated federal and state proficiency programs, laboratories in this geographic region have improved their performance as compared with previous published studies and an unpublished study.
From the New Jersey Graduate Program in Public Health (Mr Jobanputra) and the Environmental and Occupational Health Sciences Institute (Ms Buckler, Drs Cody, Gochfeld, and Rhoads, and Mr Rich), University of Medicine and Dentistry of New Jersey–Robert Wood Johnson Medical School, and Rutgers University, Piscataway, NJ; and Divisions of Environmental Health Laboratory Sciences (Dr Jones) and Environmental Hazards and Health Effects (Dr Matte), Centers for Disease Control and Prevention, National Center for Environmental Health, Atlanta, Ga.
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