Immunological characteristics before and after laboratory testing and treatment of HIV "indeterminate-positive" individuals in Pudong New Area, Shanghai, from 2014 to 2019

ObjectiveTo differentiate between "indeterminate" early and late HIV infection samples to ensure timely follow-up. MethodsA retrospective analysis was conducted on all "indeterminate" HIV infection samples from the Pudong New Area confirmatory laboratory between 2014 and 2019. Samples were grouped based on epidemiological data and follow-up results: 58 "early positive-indeterminate"and 31 "late positive-indeterminate"samples. Fourth-generation rapid diagnostic tests (RDTs) and third-generation enzyme-linked immunosorbent assays (ELISAs) were performed on both groups. The characteristics of the screening results and confirmatory bands were analyzed, and the differences in CD4+T cell levels before and after 3 years of treatment were compared between the two groups.ResultsBoth the fourth-generation RDT and third-generation ELISA antibody tests were 100% positive in both the "early positive-indeterminate" and "late positive-indeterminate" groups. However, the S/CO values from the third-generation ELISA showed a statistically significant difference between the two groups (t=31.65, P<0.001). The proportions of different band patterns in the antibody confirmatory test that transitioned to "early positive" and "late positive" were also statistically significant (χ2=65.10, P<0.001). The overall distribution of changes in CD4+T cell counts before and after 3 years of treatment differed significantly between the "early positive-indeterminate" and "late positive-indeterminate"groups (U=415.5, P<0.001). ConclusionsCombining screening results and confirmatory band characteristics can effectively distinguish different stages of infection in "indeterminate" HIV antibody results and provide corresponding follow-up recommendations. Furthermore, changes in CD4+T cell counts before and after treatment can be used to assess immune reconstitution following treatment.