Predictors of having a resistance test following confirmed virological failure of combination antiretroviral therapy: data from EuroSIDA.

BACKGROUND Guidelines suggest that patients on continuous antiretroviral therapy for >4 months with current viral load (VL)>1,000 copies/ml should be tested for resistance. There are limited data showing the frequency of resistance testing in routine clinical practice following these recommendations. METHODS In EuroSIDA, virological failure (VF) was defined as confirmed VL>1,000 copies/ml after ≥ 4 months continuous use of any antiretroviral in a ≥ 3-drug regimen started during or after 2002. We assessed whether a resistance test was performed around VF (from 4 months before to 1 year after VF) and used logistic regression analysis to assess factors associated with having a resistance test. RESULTS A total of 1,090 patients experienced VF a median 8.1 months (range 4 months to 6.3 years) after starting their regimen. There were 395 (36.2%; 95% CI 33.4-39.1) patients with a resistance test around the time of VF. Predictors of having a resistance test following VF include availability of a resistance test earlier than 4 months before VF (OR 2.20, 95% CI 1.77-2.75 for yes versus no; P<0.0001), region (OR 0.29, 95% CI 0.14-0.62 for Eastern Europe versus Northern Europe and OR 0.64, 95% CI 0.48-0.85 for Southern Europe versus Northern Europe; global P=0.0006) and current calendar year (OR 0.45, 95% CI 0.30-0.68 for ≥ 2007 versus 2004; global P=0.003). CONCLUSIONS This analysis suggests a delay in genotypic testing after VF that seems longer than expected given current treatment guidelines. This delay is highly variable across Europe.