This study is among the largest cohort studies on HIV nPEP. It includes a population of subjects potentially exposed to HIV through various routes, both sexual and nonsexual. Our results demonstrate the

feasibility and efficiency of a strategy based on active tracing of the source of exposure as a means to reduce unnecessary antiretroviral prophylaxis. Current CDC guidelines recommend the prescription of nPEP in cases of exposure to a known HIV-infected source [7]. A study by Pinkerton et al. [23] concluded that nPEP was only cost-effective in cases where men reported receptive anal intercourse with an infected partner. ZD1839 However, HIV transmission by partners of unknown HIV status has already been reported in this context [24]. In cases of nonoccupational exposures, especially for anonymous sexual contacts, the HIV status of the source is often unknown, as was the case in our study for 77% of events. CDC guidelines do not recommend for or against the use of nPEP in these situations but favour a case-by-case approach in which risks and benefits are weighed [7]. Swiss national guidelines recommend prophylaxis in situations where the source person belongs to a high-risk group for HIV infection (MSM, IDU, individuals from high HIV prevalence areas and sexual assaulters)

[15]. For this reason, in most nPEP studies published to date, antiretroviral prophylaxis has been provided for both documented and high-risk selleck chemical potential exposures to HIV [12,13,16–20]. The only way to overcome this problem and avoid unnecessary prescription of antiviral prophylaxis is to test the source subject whenever possible, as stressed by some guidelines [7,25]. Tracing and testing the source person has already proved feasible and cost-saving [20,26]. In a previous report based on a smaller sample of the same cohort, this strategy was found to reduce the number

of nPEP prescriptions by 28% [26]. In our study, source persons of unknown HIV status could be tested in 42% of events, a proportion significantly higher than previously reported (7–16%) [16,20]. The reason why we obtained such a high rate of source persons presenting for testing was probably related to the proactive way in which we explained to the exposed patients the benefits of avoiding Cell press or interrupting nPEP if the source was tested negative for HIV. These included not having to be exposed to antiretroviral drugs with known side effects for 28 days and the financial benefit of not paying for the entire course of nPEP (in Switzerland, the cost of nPEP is charged directly to the patient and then partially reimbursed through medical insurance). This approach allowed us to avoid or interrupt unnecessary nPEP in 31% of eligible events, contributing to reduced healthcare costs, potential drug toxicity and anxiety for the exposed person.