Performance of an alternative laboratory-based algorithm for HIV diagnosis in a high-risk population.
BACKGROUND
An immunoassay (IA) followed by Western blot (WB) or immunofluorescence assay has been the primary algorithm used to provide laboratory confirmation of the diagnosis of HIV infection in the US for more than 20 years. Recently, an alternative diagnostic algorithm was proposed to more accurately identify early HIV-1 infection and differentiate between HIV-1 and HIV-2 infection.


OBJECTIVE
Evaluate a sequential alternative algorithm in which reactive IAs are followed by a rapid HIV test and, if negative, a nucleic acid amplification test (NAAT).


METHODS
Specimens from high-risk persons were tested with 4 HIV IAs, 6 rapid HIV tests and NAAT (APTIMA(®)), which are approved by the United States Food and Drug Administration. IAs were repeated in duplicate if specimen volumes were sufficient. The performance of the alternative algorithm was compared to HIV WB and NAAT.


RESULTS
The original study classified 377 specimens as HIV-positive and 3070 as HIV-negative. All 4 IAs correctly identified >99.5% of HIV-positive specimens and, on initial screening, >95.8% of HIV-negative specimens. When repeated, specificity of IAs improved to >99%. Between 6.7% and 12.4% of IA-repeatedly reactive specimens required APTIMA for resolution. The alternative algorithm led to the correct classification of all IA-reactive specimens.


CONCLUSIONS
Regardless of screening IA and rapid test used, the alternative algorithm correctly classified the infection status of all persons with reactive screening IA results. Few specimens required NAAT for resolution, and the proportion requiring NAAT was lower when repeat IA test results were considered.
Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, MS E-46, Atlanta, GA 30333, USA. kdelaney@cdc.gov
Kevin P
KP
Delaney
James D
JD
Heffelfinger
Laura G
LG
Wesolowski
S Michele
SM
Owen
William A
WA
Meyer
Susan
S
Kennedy
Apurva
A
Uniyal
Peter R
PR
Kerndt
Bernard M
BM
Branson
D000465:Algorithms; D000918:Antibody Specificity; D015153:Blotting, Western; D019937:Diagnostic Techniques and Procedures; D015483:HIV Antibodies / Q000276:immunology; D015658:HIV Infections / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology / Q000821:virology; D015497:HIV-1 / Q000276:immunology / Q000472:pathogenicity; D015498:HIV-2 / Q000276:immunology / Q000472:pathogenicity; D006801:Humans; D007118:Immunoassay / Q000379:methods; D008403:Mass Screening / Q000379:methods*; D021141:Nucleic Acid Amplification Techniques; D012367:RNA, Viral / Q000235:genetics*; D012307:Risk Factors; D012680:Sensitivity and Specificity; D014481:United States / Q000453:epidemiology; D014486:United States Food and Drug Administration
D015483:HIV Antibodies; D012367:RNA, Viral