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Anti-HIV-1 assay performance: interlot and intralot variability. Australian HIV Testing Laboratories.
Vandenbelt TA; Dax EM; National HIV Reference Laboratory (NRL),
December 30, 1992
Int Conf AIDS. 1992 Jul 19-24;8(3):42 (abstract no. PuA 6186). Unique

OBJECTIVES: To examine the interlot and intralot performance of 12 anti-HIV-1 screening assays used in Australia between 1987-1990 METHODS: Anti-HIV-1 kit lots sold to and used by Australian testing laboratories between 1987 and 1990 were monitored. The repeat reactor rates (RRR) achieved in individual anti-HIV-1 testing laboratories were relayed weekly to the NRL. The NRL separately analysed the data for the Blood Banks (BB) and Public Health Laboratories (PHL). Process control charts were produced for all assays using the RRR as a measure of a lot's performance. The mean from each lot within a particular assay was compared to the assay's overall mean. Lots were classified as unsatisfactory where the mean RRR of lots lay outside 3 SD from the overall assay mean. The Range control chart (R-chart) was used to detect changes within lots. RESULTS: The data consisted of results from 3,789,036 specimens on a total of 626 lots in the BBs and 1,818,860 specimens on a total of 724 lots in the PHLs. The mean RRR from the 10 assays used by BBs during 1987-1990 was 0.1193% with a SD of 0.0915. The mean RRR from the 12 assays used by PHLs during 1987-1990 was 1.067% with a SD of 0.6895. The higher RRR in the PHLs reflects specimens from mixed risk groups and high occurrence of indeterminate specimens. The assays used by the BBs had a total of 19 lots (3.03%) considered to be unsatisfactory. The assays used by the PHLs had a total of 26 lots (3.59%) considered to be unsatisfactory. CONCLUSIONS: The occurrence of unsatisfactory lots was generally random, and could rarely be anticipated by a shift in the assay's overall mean. The in-field monitoring of screening assay interlot and intralot performance may be accomplished using the RRR. The interlot and intralot performance was found to vary considerably in both BBs and PHLs, suggesting the usefulness of in-field monitoring.

Acquired Immunodeficiency Syndrome/*DIAGNOSIS/PREVENTION & CONTROL Australia Blood Banks Human *HIV-1 Laboratories/STANDARDS Mass Screening/STANDARDS Public Health Quality Control Reagent Kits, Diagnostic/*STANDARDS ABSTRACT