Susceptibility to tipranavir. a. Distribution of tipranavir mutation score: The distribution of tipranavir mutation score in subjects with virological failure to antiretroviral regimens containing ritonavir-boosted lopinavir (LPV/r, n = 20) or atazanavir (ATV, n = 21). P = 0.037 (by Chi-square test). b. Estimated virological responses to tipranavir: Assessment of the estimated virological responses to TPV/r in patients experiencing virological failure to regimens containing LPV/r or ATV. The maximal response is estimated by TPV score <2, reduced response by TPV score of 3-7, and minimal response by TPV score ≥ 8.