Evaluation of a sensitive/less-sensitive testing algorithm using the 3A11-LS assay for detecting recent HIV seroconversion among individuals with HIV-1 subtype B or E infection in Thailand.
The development of a serologic algorithm to determine recent HIV seroconversion, using sensitive/less-sensitive testing strategies, has generated widespread interest in applying this approach to estimate HIV-1 incidence in various populations around the world. To evaluate this approach in non-B subtypes, longitudinal specimens (n = 522) collected from 90 incident infections among injecting drug users in Bangkok (subtype B infection, n = 18; subtype E infection, n = 72) were tested by the 3A11-LS assay. Standardized optical density (SOD) was calculated, using median values, and the window period between seroconversion as determined by sensitive and less sensitive tests was estimated by a maximum-likelihood model described previously. Our results show that the mean window period of the 3A11-LS assay was 155 days (95% CI, 128-189 days) for subtype B but was 270 days (95% CI, 187-349 days) for subtype E specimens from Thailand. About 4% of individuals with incident subtype E infections remained below the threshold (SOD of 0.75), even 2 years after seroconversion. Among the patients with clinical AIDS and declining antibodies, none of the 7 individuals with subtype B, but 10 (8.7%) of 115 with subtype E infections, were misclassified as recent infections. Lowering the cutoff to an SOD of 0.45 for subtype E specimens resulted in a mean window period of 185 days (95% CI, 154-211 days), with all individuals seroconverting, and reduced the number of subtype E-infected patients with AIDS who were misclassified as having recent infection to 2.6%. Our results demonstrate that the 3A11-LS assay has different performance characteristics in detecting recent infections among individuals infected with subtypes B or E. Determining appropriate cutoffs and mean window periods for other HIV-1 subtypes will be necessary before this approach can be reliably implemented in settings where non-B subtypes are common.
Parekh
B S
BS
Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. bprekh@cdc.gov
Hu
D J
DJ
Vanichseni
S
S
Satten
G A
GA
Candal
D
D
Young
N L
NL
Kitayaporn
D
D
Srisuwanvilai
L O
LO
Rakhtam
S
S
Janssen
R
R
Choopanya
K
K
Mastro
T D
TD
D000328:Adult; D000465:Algorithms; D015658:HIV Infections / Q000276:immunology*; D006679:HIV Seropositivity / Q000175:diagnosis*; D015497:HIV-1 / Q000145:classification* / Q000276:immunology; D006801:Humans; D007118:Immunoassay; D016130:Immunophenotyping; D008137:Longitudinal Studies; D008297:Male; D012680:Sensitivity and Specificity; D015819:Substance Abuse, Intravenous / Q000150:complications; D013785:Thailand; D013997:Time Factors