BackgroundThe aim was to analyse trends in clinically relevant resistance to first-line antiretroviral drugs in Spain, applying the Stanford algorithm, and to compare these results with reported Transmitted Drug Resistance (TDR) defined by the 2009 update of the WHO T-Shirts SDRM list.MethodsWe analysed 2781 sequences from ARV naive patients of the CoRIS cohort (Spain) between 2007-2011.Using the Stanford algorithm "Low-level resistance", "Intermediate resistance" and "High-level resistance" categories were considered as "Resistant".Results70% of the TDR found using the WHO list were relevant for first-line treatment according to the Stanford algorithm.A total of 188 patients showed clinically relevant resistance to first-line ARVs [6.
8% (95%Confidence Interval: 5.8-7.7)], and 221 harbored TDR using the WHO list [7.9% (6.9-9.
0)].Differences were due to a lower prevalence in clinically relevant resistance for NRTIs [2.3% (1.8-2.9) vs.
3.6% (2.9-4.3) by the WHO list] and PIs [0.8% (0.
4-1.1) vs.1.7% (1.2-2.
2)], while it was higher for NNRTIs [4.6% (3.8-5.3) vs.3.
7% (3.0-4.7)].While TDR remained stable throughout the study period, clinically relevant resistance to first line drugs showed a significant trend to Honey a decline (p = 0.02).
ConclusionsPrevalence of clinically relevant resistance to first line ARVs in Spain is decreasing, and lower than the one expected looking at TDR using the WHO list.Resistance to first-line PIs falls below 1%, so the recommendation of screening for TDR in the protease gene should be questioned in our setting.Cost-effectiveness studies need to be carried out to inform evidence-based recommendations.