Review Finds POC VL Testing Has High Specificity for HIV Viral Load

A recent review in Cochrane Database of Systemic Reviews shows that point-of-care viral load (POC VL) tests can detect or exclude high viral loads for people with HIV vs central laboratory-based assays.

The review included 14 studies in the meta-analyses. Cochrane Central Register of Controlled Trials, MEDLINE Ovid, Embase Ovid, World Health Organization (WHO) International Clinical Trials Registry Platform, and WHO Global Index Medicus were searched.

Data on study characteristics, study design, demographic and participant characteristics, methods of collecting and preparing blood specimens, time point of VL testing after antiretroviral therapy (ART) initiation, index test and reference standard characteristics, test cut-off and performance, and main outcome data or results were extracted and collected.

For the 14 studies, there included 20 evaluations and 8659 participants. Participants in 9 evaluations were receiving ART and the other 11 evaluations had partial or unclear ART treatment. There were 13 evaluations that included only adults, 5 with adults and children, and 2 that did not state participant age. Further, the 20 evaluations reported a threshold of ≥1000 copies/mL, which is the current WHO-recommended clinical threshold for treatment failure. Median prevalence for high viral load was 33.4%.

Sensitivity estimates ranged from 89% to 100% in the 20 evaluations, and specificity from 19% to 100%. POC VL pooled sensitivity and specificity against laboratory-based assays at a threshold ≥1000 copies/mL were 96.6% (95% CI, 94.8%-97.8%) and 95.7% (95% CI, 90.8%-98.0%), respectively.

A subgroup analysis was conducted for location, test type, and threshold covariates. In POC tests conducted near the patient, pooled sensitivity was 96.7% (95% CI, 94.1%-98.2%) and specificity was 95.6% (95% CI, 90.8%-98.0%). For POC tests conducted in a central laboratory, these totals came in at 96.5% (95% CI, 93.7%-98.1%) and 95.8% (95% CI, 84.0%-99.0%), respectively.

The pooled sensitivity of the Xpert HIV-1 Viral Load test was 96.9% (95% CI, 94.0%-98.4%) and specificity was 95.6% (95% CI, 89.4%-98.2%). For the SAMBA HIV-1 Semi-Q Test, there 94.8% (95% CI, 91.6%-96.9%) sensitivity and 97.2% (95% CI, 95.3%-98.4%) specificity.

Pooled sensitivity and specificity against laboratory tests were 96.5% (95% CI, 92.6%-98.4%) and 90.1% (95% CI, 71.6%-97.0%) in studies with clearly reported ART-exclusive populations. A sensitivity of 96.1% (95% CI, 94.2%-97.4) and a specificity of 97.0% (95% CI, 95.2%-98.1%) were reported when restricting to commercial assays, as were 96.0% (95% CI, 94.0%-97.3%) sensitivity and 97.0% (95% CI, 96.1%-97.8%) specificity when restricting to plasma samples.

There were some limitations to this review. Data were insufficient to pool results of other reported thresholds, and some evaluations used 2 reference tests to handle discrepant results, which forced the researchers to use the result of the first reference test.

The researchers concluded that the POC VL tests have a high sensitivity and high specificity to detect or exclude high viral loads at ≥1000 copies/mL threshold for patients with HIV.

“These tests may complement or replace traditional central laboratory-based viral assays. Also, in resource-poor settings where patients have limited access to health facilities and would otherwise exceed the recommended time for a POC VL, field or near POC VL testing may be useful as an initial screening test,” the authors concluded.

Reference

Ochodo EA, Olwanda EE, Deeks JJ, Mallett S. Point-of-care viral load tests to detect high HIV viral load in patients living with HIV/AIDS attending health facilities. Cochrane Database Syst Rev. Published online March 10, 2022. doi:10.1002/14651858.CD013208.pub2