Declining HIV Drug Resistance in Europe

One of the greatest concerns about ever-expanding access to antiretroviral therapy (ART) is an increase in drug resistance. To assess trends in — and determinants of — such resistance in Western Europe, researchers examined HIV genotype data on samples obtained from ART-experienced patients in the U.K., Italy, Portugal, Germany, Sweden, Spain, and Belgium between 1997 and 2008.

Records for 20,323 samples were included in the analysis. Overall, 16,278 samples (80%) showed at least one resistance mutation. Resistance to nucleoside reverse transcriptase inhibitors (NRTIs) was most common (67%), followed by nonnucleoside reverse transcriptase inhibitors (NNRTIs; 51%) and protease inhibitors (PIs; 33%). Resistance to one, two, and three of these drug classes was seen in 26%, 38%, and 16% of the samples, respectively. For NRTIs, the most common resistance mutations were M184V/I and thymidine analogue mutations; for NNRTIs, K103N, Y181C/I, and G190A; and for PIs, L90M, M46I/L, V82A/F/L/S/T, and I84V. The proportion of samples with at least one resistance mutation declined over time, from 81% in 1997 to 71% in 2008; NRTI and PI mutations showed notable decreases. The proportion of sampled patients who exhausted available drug options dropped dramatically, from 32% in 2000 to 1% in 2008.

During the sampling period, NRTI use decreased (from 98% of the patients in 1997 to 94% in 2008), NNRTI use increased (from 6% in 1997 to 41% in 2000, leveling off at 32% in 2008), unboosted PI use decreased (from 55% in 1997 to 7% in 2008), and boosted PI use increased (from 1% in 1997 to 48% in 2008).

In multivariable analysis, factors associated with detection of resistance included being a man who has sex with men, non-B subtype virus, history of suboptimal therapy, failure of higher-line regimens, and longer duration of ART exposure.