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1
Wadsworth Center, New York State Department of Health, PO Box 509, Albany, NY 12201-0509.
2
Division of General Pediatrics, North Shore University
Hospital, Great Neck, NY 11021.
3
Division of General Academic Pediatrics, Nemours
Children’s Clinic, Arnold Palmer Hospital for Children and Women,
Orlando, FL 32806.
4
Long Island Poison Control Center, Winthrop University
Hospital, 259 First St., Mineola, NY 11501.
5
Wisconsin State Laboratory of Hygiene, 2601 Agriculture
Dr., PO Box 7996, Madison, WI 53707-7996.
6
Department of Environmental and Community Medicine,
University of Medicine and Dentistry of New Jersey, 675 Hoes Ln.,
Piscataway, NJ 08854-5635.
a Author for correspondence. Fax 518-473-7586; e-mail
patrick.parsons{at}wadsworth.org.
Background: Most proficiency testing (PT) programs operate with an open design in which clearly identified performance samples are distributed directly to participating laboratories on a shipping schedule announced in advance. In this study, we examine the effectiveness of assessing clinical laboratory performance for blood lead with an open PT by comparing its results with a double-blinded testing protocol.
Methods: Aliquots from up to 72 blood lead performance pools from the New York State Department of Health and the Wisconsin State Laboratory of Hygiene were disguised as routine patient specimens and submitted in two phases to up to 42 certified clinical laboratories for blood lead analysis. These 42 laboratories also received aliquots of the same performance samples for blood lead analysis directly from the "open" PT program provider.
Results: Data reported under blind and open strategies were scored against acceptable target ranges using the Clinical Laboratory Improvement Amendments of 1988 (CLIA ’88) criteria established for blood lead, i.e., ± 0.19 µmol/L (± 4 µg/dL) or ± 10%, whichever is greater. Performance differences between the strategies were also assessed. We found that 17.7% of all blind PT results were classified as unacceptable compared with only 4.5% of open PT results (P <0.001). In phase 1, 13 of 22 laboratories (60%) exhibited a statistically significant difference (P <0.05) between their blind and open PT performances, although for 6 laboratories the poorer blind performance may not necessarily have led to unsuccessful PT participation under CLIA ’88 criteria. Seven (32%) laboratories had unsuccessful aggregate performance (<80%) under blind testing while maintaining successful performance in open testing. Of these seven, two had gross discrepancies motivating further investigation.
Conclusions: The data suggest that although 
60% of clinical
laboratories make special efforts to improve analytical performance on
open PT samples relative to performance achieved for routine patient
specimens, in most cases the differences are clinically insignificant
and would not likely affect cumulative PT performance. Occasional use
of blind PT may deter the inclination to treat performance samples more
carefully.
The following articles in journals at HighWire Press have cited this article:
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  S. Shahangian and S. R. Snyder Laboratory Medicine Quality Indicators: A Review of the Literature Am J Clin Pathol, March 1, 2009; 131(3): 418 - 431. [Abstract] [Full Text] [PDF]
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 J. H. Shelton, C. A. Santa Ana, D. R. Thompson, M. Emmett, and J. S. Fordtran Factitious Diarrhea Induced by Stimulant Laxatives: Accuracy of Diagnosis by a Clinical Reference Laboratory Using Thin Layer Chromatography Clin. Chem., January 1, 2007; 53(1): 85 - 90. [Abstract] [Full Text] [PDF]
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