Gandhi NR, Tate JP, Rodriguez-Barradas MC, Rimland D, Goetz MB, Gibert C, Brown ST, Mattocks K, Justice AC. Validation of an algorithm to identify antiretroviral-na?ve status at time of entry into a large, observational cohort of HIV-infected patients. Pharmacoepidemiol Drug Saf. 2013 Sep; 22(9):1019-25.