Clinical Utility of the Signal-to-Cutoff Ratio of Reactive HIV Antigen/Antibody Screening Tests in Guiding Emergency Physician Management

Using signal-to-cutoff ratios of HIV screening assay to predict HIV infection

BACKGROUND

The sensitivity of HIV screening assays often leads to a high rate of false-positive results, requiring retests and confirmatory tests. This study aimed to analyze the capability of signal-to-cutoff (S/CO) ratios of HIV screening assay to predict HIV infection.

METHODS

A retrospective study on the HIV screening-positive population was performed at Zhongshan Hospital, Xiamen University, the correlation between HIV screening assay S/CO ratios and HIV infection was assessed, and plotted Receiver Operating Characteristic (ROC) curves were generated to establish the optimal cutoff value for predicting HIV infection.

RESULTS

Out of 396,679 patients, 836 were confirmed to be HIV-infected, with an HIV prevalence of 0.21%. The median S/CO ratios in HIV infection were significantly higher than that in non-HIV infection (296.9 vs. 2.41, P < 0.001). The rate of confirmed HIV infection was increased with higher S/CO ratios in the screening assay. The ROC curve based on the HIV screening assay S/CO ratio achieved a sensitivity of 93.78% and a specificity of 93.12% with an optimal cutoff value of 14.09. The area under the ROC curve was 0.9612. Further analysis of the ROC curve indicated that the S/CO ratio thresholds yielding positive predictive values of 99%, 99.5%, and 100% for HIV infection were 26.25, 285.7, and 354.5, respectively.

CONCLUSION

Using HIV screening assay S/CO ratio to predict HIV infection can largely reduce necessitating retests and confirmatory tests. Incorporating the S/CO ratio into HIV testing algorithms can have significant implications for medical and public health practices.

Trypanosoma cruzi Secreted Cyclophilin TcCyP19 as an Early Marker for Trypanocidal Treatment Efficiency

Cyclophilins (CyPs) are a family of enzymes involved in protein folding. Trypanosoma cruzi, the causative agent of Chagas disease, has a 19-kDa cyclophilin, TcCyP19, that was found to be secreted in parasite stages of the CL Brener clone and recognized by sera from T. cruzi-infected mice and patients. The levels of specific antibodies against TcCyP19 in T. cruzi-infected mice and subjects before and after drug treatment were measured by an in-house enzyme linked immunosorbent assay (ELISA). Mice in the acute and chronic phase of infection, with successful trypanocidal treatments, showed significantly lower anti-TcCyP19 antibody levels than untreated mice. In children and adults chronically infected with T. cruzi, a significant decrease in the anti-TcCyP19 titers was observed after 12 months of etiological treatment. This decrease was maintained in adult chronic patients followed-up 30-38 months post-treatment. These results encourage further studies on TcCyP19 as an early biomarker of trypanocidal treatment efficiency.

Implementing a Rapid Antiretroviral Therapy Program Using Starter Packs for Emergency Department Patients Diagnosed With HIV Infection

Background

Emergency departments (ED) have been identified as essential partners in the national plan to end the HIV epidemic. The initiation of rapid antiretroviral therapy (ART) may be an important strategy to minimize the treatment barriers faced by many ED patients diagnosed with HIV.

Methods

We describe the implementation and outcomes of a protocol to provide rapid ART by using starter packs for eligible ED patients testing HIV antigen/antibody (Ag/Ab) reactive. Eligible patients were not pregnant, were unlikely to have a false-positive Ag/Ab test result, were discharged home, were ART naive, had acceptable liver and renal function, lacked symptoms of an opportunistic infection, and were judged to be a good candidate.

Results

During the 1-year study period, 10 606 HIV tests were performed, and 106 patients were HIV Ag/Ab reactive and assessed for ED rapid ART eligibility. Thirty-one patients (29.2%) were eligible for ED rapid ART; 26 (24.5%) were offered it; and 25 accepted and were provided starter packs for an overall ED rapid ART treatment rate of 23.6%. Two patients receiving ED rapid ART were confirmed to be HIV negative. Patients provided ED rapid ART were more likely to follow up by 30 days (82.6% vs 50.0%, P = .01) than patients not provided ED rapid ART. The 6-month incidence of immune reconstitution inflammatory syndrome was 4.3% among the 23 patients who were HIV positive and receiving ED rapid ART.

Conclusions

The initiation of ED rapid ART for patients testing HIV Ag/Ab reactive is feasible, well accepted, and safe and may be an important facilitator of linkage to care.

A case of a false positive HIV antigen/antibody screen in a pregnant woman at delivery and the clinical importance of reviewing signal-to-cutoff ratio values

We present a unique case not previously touched upon in the literature, and its ensuing management, of a falsely reactive HIV (human immunodeficiency virus) screening test which resulted in a woman during active labor, hours after rupture of membranes. The patient was screened for HIV using the ARCHITECT 4th generation HIV 1 and 2 Antigen/Antibody (Ag/Ab) Combo assay, and the results were repeatedly reactive. A cesarean delivery was recommended, and the patient received intrapartum antiretroviral therapy. Due to rapid progression of labor, the infant was delivered vaginally and received multiple doses of antiretroviral therapy. For confirmation, a viral load PCR test was obtained which resulted undetectable, and it was concluded that the screening results were falsely positive. While the cause of the inaccurate screening result is still unclear, a COVID-19 vaccination in close proximity to the delivery remains suspicious. Four months after delivery, the patient's screening test was no longer reactive.