BackgroundIn China, although tremendous efforts has been made, the HIV/AIDS is still not controlled.ObjectivesThe study was carried out to determine the epidemic of HIV infection in Xi’an, analyse false positives (FP) risk factors and potential utility of sample-to-cutoff index to identify true positives using Architect HIV Ag/Ab Combo.MethodsA retrospective review for HIV screening by Architect HIV Ag/Ab Combo was performed in a teaching hospital in Xi’an between 2015 and 2016. The prevalence of HIV, positive predictive value (PPV) at different cut-off indexices (COI) were calculated. The epidemic of infections and risk factors for FP results were investigated.ResultsIn the study, the HIV prevalence and FP rate of Architect HIV Ag/Ab Combo were 0.076 and 46.08%, respectively. The Han Chinese, males and people aged < 40 years accounted for the majority of infections (98.29, 76.07 and 73.5%, respectively). 85.47% of the infections were transmitted through sexual contact (35.04% of male homosexual and 50.43% of heterosexual). COI at 1–10, 10–30 and ≥ 30, the PPVs were 0, 50 and 100%, respectively. The independent risk factors for FP, i.e., pregnancy and malignancy had a statistically significant association with FP (p < 0.05), and age had a very strong statistically significant association with FP (p < 0.001).ConclusionsIn Xi’an, sexual contact was the most important transmission mode for HIV, and the infections were predominantly identified in Han Chinese, males, young and middle-aged people. For Architect HIV Ag/Ab Combo, it can achieve 100% of PPV with COI ≥30, and the age was strongly statistically associated with FP.

BackgroundThe Architect HIV Ag/Ab Combo has excellent performance for HIV screening; however, the false‐positive rate (FPR) was high in low HIV prevalence setting.ObjectivesThe purpose of this study was to analyze the influence of sample‐to‐cutoff (s/co) ratios by Architect HIV Ag/Ab Combo with the results of confirmatory test and explore the potential utility of s/co to predict HIV infection.MethodsA retrospective review on Architect HIV Ag/Ab Combo reactive results was performed at a teaching hospital in Xi'an. The s/co values in different groups, that is, true positives (TP) and false positives (FP), different Western blotting (WB) bands among WB‐positive cases, were compared. The receiver operating characteristic curve (ROC) analysis was used to determine the optimal cutoff value for predicting HIV infection.ResultsDuring the study period, 219 out of 84 702 patients were reactive by ARCHITECT with a 0.0992% of HIV prevalence and a 56.25% of FPR. The mean s/co ratios in TP were significantly higher than that in FP (458.15 vs 3.11, P < 0.0001). Among the WB‐positive cases, the s/co ratios increased significantly with the increase in the number of bands, P = 0.0065. The optimal cutoff (24.44) by ROC analysis can provide the highest sum of sensitivity (100%) and specificity (100%) with no FP results.ConclusionsFor Architect HIV Ag/Ab Combo, the FPR is reduced when s/co ratios increase, and the s/co ≥24.44 may be reliable to predict HIV infection.

Objectives: In the study, firstly, the epidemic characteristics of new HIV/AIDS were investigated in order to provide evidence for the targeted interventions; Secondly, the major factors of false positives (FP) for HIV testing were also determined. Methods: A retrospective review was performed in a teaching hospital in Xi’an between 2013 and 2018. The overall characteristics and epidemiological trends of new HIV/AIDS were described. Moreover, the distributions of FP cases in the gender, age and department were analysed, and the major factors of FP were determined by the Pareto analysis. Results: During the study, a total of 469 new HIV/AIDS were diagnosed, with an increasing prevalence from 0.0626% in 2013 to 0.0827% in 2018. Of them, the majority occurred in the Hans (99.57%), males (88.50%), people aged 21-50 years (76.97%), migrants (60.98%) and sexual contact route (88.70%). A rapid increase in the annual number of new HIV/AIDS and multiple routes of HIV transmission were found. The epidemic showed increasing trends in groups of young individuals, students and homosexual mode, however, a downward trend in the percentage of injecting drug use was also observed. 67.81% of FP cases were over 50 years old. The departments of oncology, obstetrics, hepatobiliary surgery, nephrology, cardiology and infectious disease were major factors of FP by Pareto analysis. Conclusions: The HIV/AIDS epidemic in Xi’an is still evolving, therefore, effective strategies, appropriate education and scaling up HIV testing should be developed to control the spread of the epidemic. In addition, old adults and specific departments were associated with FP.