A-267 How Does Rapid HIV Antibody Testing Fit Into the Current Testing Algorithm?
Authors: Bui-Bullock T , Farnsworth C W , Anderson N W 
Published: October 2024

Abstract

Background
Many emergency departments (ED) currently use rapid HIV antibody tests as screening tools, despite limited sensitivity for detecting acute HIV infections. We performed an analysis of standard of care rapid and in-lab fourth generation HIV testing, to 1) assess the performance of rapid HIV testing in our patient population and 2) identify key symptoms of acute HIV infections.

Methods
A four-year retrospective analysis from 1/1/2018-12/31/2021 was conducted at Barnes Jewish Hospital and St. Louis Children’s Hospital in St. Louis, Missouri. During the study period, both rapid HIV testing (SURE CHECK HIV 1/2, Chembio) and in-lab fourth generation HIV testing (ARCHITECT HIV Ag/Ab Combo Assay, Abbott) were available to providers. Comparative performance of rapid testing and in-lab fourth generation testing was assessed using complete Fourth Generation HIV algorithmic testing as the gold standard. Symptomatology was recorded for a subset of patients that presented to the ED to determine associations with different testing patterns.

Results
A total of 28,240 rapid HIV antibody tests were administered throughout inpatient, outpatient, and emergency departments at both hospitals, revealing an average yearly positivity rate of 0.6%. In a subset of 1192 patients who underwent both rapid HIV antibody and fourth generation in-lab testing, the rapid HIV antibody test exhibited a positive percent agreement of 92.5% (95% CI: 84.6-96.5) and negative percent agreement of 98.1% (95% CI: 97.1-98.8). Rapid testing demonstrated a negative predictive value (NPV) of 99.5% (95% CI: 98.8-99.8) and a positive predictive value of 77.9% (95% CI: 68.6-85.1). Notably, the rapid test failed to detect 3/3 (100%) acute HIV infections defined as rapid HIV antibody test negative, Ag/Ab assay and nucleic acid amplification assay positive. The rapid test demonstrated comparable performance in patients with known HIV infections, regardless of antiretroviral therapy (ART) status. The positivity rate was 23/24 (95.8%) in known HIV patients with ART compared to 25/27 (92.6%) in those without (P&gt;0.9999). Among patients on ART, the mean ± SD log10 viral load was 3.15±1.52, whereas those without ART exhibited a viral load of 4.87±0.99 (P=0.0140). In the ED, symptoms such as fever, nausea/vomiting, malaise, headache, and photophobia were significantly correlated with acute HIV infection. Acute HIV patients were more likely to display fever in conjunction with three other symptoms (P&lt;0.0001).

Conclusions
The rapid HIV antibody test demonstrated high sensitivity, specificity, and NPV in our study population, reaffirming its effectiveness as a valuable screening tool. ART did not seem to affect the rapid test performance. However, the low PPV and 100% failure in detecting acute HIV infections underscore the importance of confirmatory in-lab testing. Insights into symptomatology of patients with acute HIV inform ED providers when confirmatory testing is essential for a timely and accurate HIV diagnosis.