Clinical and sociodemographic correlates of emergent or evolving HIV drug resistance in low viral load specimens in British Columbia, Canada.

BACKGROUND/

METHODS

Treatment guidelines recommend genotypic HIV drug resistance testing (DRT) at virologic failure, typically for plasma viral loads (pVL) > 1000 HIV RNA c/mL. In some settings, DRT can be performed on low viral load (LVL) samples (pVL of 50-250 c/mL); however, such testing is resource-intensive and its clinical benefit is unclear. Therefore, we investigated the frequency and factors associated with emergent resistance in LVL samples using a comprehensive, provincial database of HIV Protease-Reverse Transcriptase and Integrase sequences.

RESULTS

A total of 43,979 Protease-RT DRTs were performed in British Columbia between 1999 and 2022, of which 2970 (6.8 %) were on LVL samples. Testing was successful for 1575 (53.0 %) LVL samples compared to 81.4 % and 94.4 % of samples with pVL 250-999 and pVL ≥ 1000 c/mL, respectively (p < 0.001). Compared to prior genotypes collected from samples with pVL > 250 c/mL, a total of 104 (7.3 %) cases of new or evolving drug resistance were identified from 1423 LVL DRTs. Of these, 49.5 %, 42.9 % and 22.9 % exhibited new Nucleoside Reverse Transcriptase, Non-Nucleoside Reverse Transcriptase and Protease resistance, respectively. Of 9309 Integrase DRTs performed between 2008 and 2022, only 4 (1.2 %) cases of new or evolving integrase resistance were observed. Multivariable analyses identified clinical/sociodemographic factors significantly associated with emergent resistance, including time elapsed between DRTs, historic cumulative resistance and NNRTI-based antiretroviral therapy.

CONCLUSIONS

Emergent or evolving resistance is identified infrequently in low viral load specimens. Given its resource-intensive nature, resistance testing of low viral load specimens may not be generally warranted.