Application of limiting antigen avidity enzyme immunoassay for estimating HIV-1 incidence in men who have sex with men / 中华流行病学杂志

Objective: To estimate the incidence of HIV-1 infection in men who have sex with men (MSM) in key areas of China through HIV-1 limiting antigen avidity enzyme immunoassay (LAg-Avidity EIA), analyze the deviation from the actual results and identify influencing factors, and provided reference for improving the accuracy of estimation results. Methods: Based on the principle of the cohort randomized study design, 20 cities were selected in China based on population size and the number of HIV-positive MSM. The sample size was estimated to be 700 according to the HIV-1 infection rate in MSM. MSM mobile phone app. was used to establish a detection appointment and questionnaire system, and the baseline cross-sectional survey was conducted from April to November 2019. LAg-Avidity EIA was used to identify the recent infected samples. The incidence of HIV-1 infection was calculated and then adjusted based on the estimation formula designed by WHO. The influencing factors were identified by analyzing the sample collection and detection processes. Results: Among the 10 650 blood samples from the participants, 799 were HIV-positive in initial screening, in which 198 samples (24.78%) missed during confirmation test. Only 621 samples were received by the laboratory. After excluding misreported samples, 520 samples were qualified for testing. A total of 155 samples were eventually determined as recent infection through LAg-Avidity EIA; Based on the estimation formula , the incidence of HIV-1 infection in MSM in 20 cities was 4.06% (95%CI:3.27%-4.85%), it increased to 5.53% (95%CI: 4.45%-6.60%)after the adjusting for sample missing rate. When the sample missing rate and misreporting rate were both adjusted, the incidence of HIV-1 infection in the MSM increased to 5.66% (95%CI:4.67%-6.65%). The actual incidence of HIV-1 infection in MSM in the 20 cities might be between 4.06% and 5.66%. Conclusions: Sample missing and misreporting might cause the deviation of the estimation of HIV-1 infection incidence. It is important to ensure the sample source and the quality of sample collection and detection to reduce the deviation in the estimation of HIV-1 infection incidence.

Factors associated with HIV infection among men who have sex with men in Nanjing, Suzhou and Yangzhou: a 1:4 matched case-control study / 中华流行病学杂志

Objective This study assessed the main factors associated with HIV infection among men having sex with men(MSM),in order to provide evidence for future intervention. Methods A case-control study was conducted among HIV cases identified at the MSM survey in Nanjing, Suzhou and Yangzhou cities from May to July in 2008. Each HIV case was matched by 4 HIV negative MSM who participated consecutively right after the HIV case was identified at the same survey, same time and in the same city. A national core MSM survey questionnaire was used with addition of variables of local interest. Fitting conditional logistic regression model was applied for univariate and multivariate analysis. Results During the survey, 62 HIV positive cases were identified and 248 controls were matched. Data from univariate analysis showed that, inconsistent condom use, syphilis infection, self reported sexually transmitted infection (STI) symptoms and/or signs, unprotected anal sex (UAI) were risk factors, with OR values of 5.56(95%CI: 1.82-16.96), 2.19(95%CI: 1.18-4.05), 2.50(95%(CI: 1.13-5.50) and 3.13 (95%CI: 1.64-5.98) respectively. Online cruising and receptive anal sex were protective factors with OR values as 0.47(95%CI: 0.22-0.998) and 0.67(95% CI: 0.23-1.97). Through multivariate analysis, it was found that syphilis, age of having experienced first insertive sexual intercourse and UAI were risk factors to HIV transmission, with OR values of 2.28 (95%CI: 1.05-4.94), 4.16 (95%CI: 1.63-10.66) and 1.11 (95% CI: 1.04-1.18) respectively. Compared with non-anal sex, bisexual (OR=0.41,95%CI: 0.18-0.97) behavior seemed a protected factor. Conclusion Syphilis infection, UAI and self reported STI symptoms and/or signs were risk factors related to HIV transmission while bisexual seemed a protective factor.