Reports on HIV/AIDS: 1990

JUNE 8, 1990, MMWR, Vol. 39, No. 22, pp.380-383
Update: Serologic Testing for HIV-1 Antibody -
United States, 1988 and 1989
In 1985, the first enzyme immunoassay (EIA) for detection of human immunodeficiency virus type 1 (HIV-1) antibody was licensed by the Food and Drug
Administration; since then, the number of HIV-1 tests performed and the number of
laboratories performing HIV-1 tests has increased steadily. Because of the need to
assess the quality of existing laboratory technology and to ensure the quality of
testing, the Model Performance Evaluation Program (MPEP) was implemented by
CDC in 1986 to evaluate the performance of laboratories testing for HIV-1 infection
(1 ). Approximately 1400 U.S. and international laboratories participated in the MPEP
during 1988 and 1989. The total number of laboratories performing HIV-1 testing is
unknown.
Laboratories in the MPEP voluntarily report results from coded plasma samples for
which HIV-1-antibody reactivity has been determined through composite testing at
CDC and verified at candidate reference laboratories (Table 1). Participants also
complete survey forms describing laboratory characteristics and testing practices.
This report summarizes data for the 752 U.S. MPEP laboratories that returned
complete results in both May 1988 and August 1989*. Performance is described in
terms of analytic sensitivity, analytic specificity, and overall analytic performance.t
Performance was calculated based on a laboratory's test results for samples that were
typical of most samples routinely tested for HIV-1 antibody.
Enzyme Immunoassays
The analytic sensitivity of EIAs for HIV-1 antibody performed for MPEP in 1988 was
99.7% (6545 reactive test results out of 6566 positive samples) (Table 2); analytic
specificity was 98.5% (3004 nonreactive test results out of 3051 negative samples).
The overall analytic performance of EIAs was 99.3% (9549 correct results out of 9617
tests).
Laboratories performing HIV-1-antibody tests were classified into 15 laboratory
types. Five types of laboratories accounted for 709 (94.7%) of the 749 MPEP
laboratories performing EIAs: non-blood-bank hospital (241 [32.2%]), laboratories
identifying themselves as independent (140 [18.7%]), hospital blood bank (124
[16.6%]), nonhospital blood bank (122 [16.3%]), and health department (82 [10.9%]).
For EIAs performed in 1988, laboratory type-specific analytic sensitivity among the
major laboratory types ranged from 99.3% to 100.0%; analytic specificity, from 98.1%
to 99.5%; and overall analytic performance, from 98.9% to 99.8%.
*Provisional data for 1989.
'Analytic sensitivity is the proportion of reactive test results in positive specimens. To calculate analytic sensitivity, Western blot (WB) "indeterminate" test results are combined with
nonreactive test results. Analytic specificity is the proportion of nonreactive test results in
negative specimens. To calculate analytic specificity, WB "indeterminate" test results are
combined with reactive test results. Overall analytic performance is the proportion of "correct"
test results in all specimens tested. Because seroreactivity of included samples was defined
as positive or negative, WB "indeterminate" test results are not considered "correct" for
calculating overall analytic performance.

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