Investigation of false positive results with an oral fluid rapid HIV-1/2 antibody test.
BACKGROUND
In March 2004, the OraQuick rapid HIV antibody test became the first rapid HIV test approved by the US Food and Drug Administration for use on oral fluid specimens. Test results are available in 20 minutes, and the oral fluid test is non-invasive. From August 2004-June 2005, we investigated a sudden increase in false-positive results occurring in a performance study of OraQuick oral-fluid rapid HIV tests in Minnesota.


RESULTS
In a field investigation, we reviewed performance study data on oral-fluid and whole-blood OraQuick rapid HIV test device lots and expiration dates and assessed test performance and interpretation with oral-fluid and whole-blood specimens by operators who reported false-positive results. We used multivariate logistic regression to evaluate client demographic and risk characteristics associated with false-positive results. Next, we conducted an incidence study of false-positive OraQuick rapid HIV tests in nine US cities and tested both oral-fluid and finger-stick whole-blood specimens from clients; reactive tests were confirmed with Western blot. Sixteen (4.1%) false-positive oral-fluid results occurred in the performance study from April 15, 2004 through August 31, 2004 with unexpired devices from six test lots among 388 HIV-uninfected clients (specificity, 95.9%; 95% CI: 93.4-97.6). Three test operators who had reported false-positive results performed and interpreted the test according to package-insert instructions. In multivariate analysis, only older age was significantly associated with false-positive results (adjusted odds ratio = 4.5, 95% CI: 1.2-25.7). In the incidence study, all valid oral-fluid and whole-blood results from 2,268 clients were concordant and no false-positive results occurred (100% specificity).


CONCLUSIONS
The field investigation did not identify a cause for the increase in false-positive oral-fluid results, and the incidence study detected no false-positive results. The findings suggest this was an isolated cluster; the test's overall performance was as specified by the manufacturer.
Jafa
Krishna
K
Division of HIV/AIDS Prevention, National Center for HIV, STD and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America. kjafa@cdc.gov
Patel
Pragna
P
Mackellar
Duncan A
DA
Sullivan
Patrick S
PS
Delaney
Kevin P
KP
Sides
Tracy L
TL
Newman
Alexandra P
AP
Paul
Sindy M
SM
Cadoff
Evan M
EM
Martin
Eugene G
EG
Keenan
Patrick A
PA
Branson
Bernard M
BM
D015492:AIDS Serodiagnosis / Q000379:methods*; D000328:Adult; D005189:False Positive Reactions; D005260:Female; D015658:HIV Infections / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology; D006679:HIV Seropositivity / Q000175:diagnosis*; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D008297:Male; D011358:Product Surveillance, Postmarketing / Q000379:methods; D011933:Reagent Kits, Diagnostic / Q000592:standards*; D012307:Risk Factors
D011933:Reagent Kits, Diagnostic