TY - JOUR T1 - Error in the calculation of person-time in the before-PrEP period by Beymer <em>et al</em> JF - Sexually Transmitted Infections JO - Sex Transm Infect SP - 514 LP - 514 DO - 10.1136/sextrans-2018-053795 VL - 94 IS - 7 AU - Sebastiaan H Hulstein AU - Elske Hoornenborg AU - Maarten F Schim van der Loeff Y1 - 2018/11/01 UR - http://sti.bmj.com/content/94/7/514.abstract N2 - Studies on STI incidence and pre-exposure prophylaxis (PrEP) use are often hampered by the absence of STI incidence data in the period before PrEP; Beymer et al 1 set out to improve on this. They report on the STI incidence before and after initiation of PrEP in a cohort of men who have sex with men at the Los Angeles LGBT Center, California, USA. We fear … ER -