Real-world viral effectiveness of two-drug versus three-drug regimens for HIV in Taiwan: Impact of adherence and treatment selection.

Background: Adherence to antiretroviral therapy (ART) is critical for successful viral suppression in people living with HIV (PLHIV). The comparative effectiveness of two-drug regimens (2DRs) versus three-drug regimens (3DRs)-particularly in Asian populations-is an underexplored topic.

Methods: This retrospective cross-sectional study was conducted at two hospitals in Taiwan between November 2023 and January 2025. Adherence was measured in terms of the proportion of days covered (PDC) over 365 days. Logistic regression analyses were used to evaluate the effectiveness of viral suppression and factors associated with regimen selection.

Results: Of the 628 PLHIV included, most were men, aged between 30 and 50 years, identified as lesbian, gay, bisexual, or transgender, and had received their diagnosis of HIV >5 years prior to this study. Among the participants receiving 3DRs (81.37 %), 3.72 % had viral loads exceeding 200 copies/mL. Regarding those receiving 2DRs (18.63 %), 2.56 % exhibited similar viral loads (p = 0.781). Multivariable analysis indicated that PDC ≥75 % was strongly associated with viral suppression (adjusted odds ratio [aOR] = 45.80, p < 0.0001), with no significant difference in viral suppression rates between regimens. The participants receiving 3DRs were less likely to have >75 % adherence (aOR = 0.18, p = 0.018) and to have a long HIV history (>5 years; aOR = 0.22, p = 0.041).

Conclusion: Adherence, not regimen type, is the key factor affecting viral suppression. Nevertheless, the findings should be cautiously interpreted because of potential bias and small subgroup sizes. Further prospective studies should evaluate the comparative efficacy of these regimens.