To the Editor—Of crucial importance in the success of HIV postexposure prophylaxis (PEP) is adherence to the 28 days course of antiretroviral treatment (ART). ¹ Nevertheless, uptake of HIV PEP is acknowledged to be insufficient, with <60% of the individuals who started PEP treatment finishing the full course.Reference Ford, Irvine and Shubber ² It is important to determine why HIV PEP adherence remains a challenge across different populations, settings, and exposures.Reference Ford, Irvine and Shubber ² Previous studies have reported higher PEP treatment completion rates with a 2-drug regimen compared to a 3-drug regimen.Reference Ford, Irvine and Shubber ^{2 ,} Reference Bassett, Freedberg and Walensky ³ One reason for noncompletion of treatment is the adverse effects of ART used for PEP.Reference Weber, Wang and Panlilio ^{4 ,} Reference Tokars, Marcus and Culver ⁵ In this study, HIV PEP treatment adherence was defined as initiating PEP treatment following occupational exposure to HIV, returning to pick up subsequent doses, and completing the rest of the PEP course as well as follow-up visits. Those that failed to adhere to PEP treatment were classified as defaulters. We examined the predictors of PEP default in a tertiary-care hospital in northwestern Nigeria.

This retrospective cohort study was conducted at a major tertiary-care hospital that is home to the largest antiretroviral treatment (ART) center in northwestern Nigeria. The ethics committee of the hospital approved this study.

We examined details of all reported incidences of occupational exposures to an HIV-positive source that occurred within the hospital from October 2004 to December 2016. In total, 70 healthcare workers exposed to HIV positive sources took PEP during the study period, and 51 patients completed the treatment while 19 defaulted (27%).

As shown in Table 1, our study revealed that those on a non–tenofovir-containing regimen were 2.6 times more likely to default PEP compared to those on a tenofovir-containing regimen (P=.0199). This finding may be related to the better tolerability of the tenofovir-based regimen compared to the zidovudine-based regimen, as reported by previous studies.Reference Ford, Shubber and Calmy ^{6 ,} Reference Tosini, Muller and Prazuck ⁷ We also found that patients prescribed 3 pills for HIV PEP were more likely to default than those prescribed 2 pills. This finding was not statistically significant. Previous studies have reported a higher PEP regimen completion rate with low pill burden.Reference Fisher, Benn and Evans ^{8 ,} Reference Sultan, Benn and Waters ⁹ Another finding, which was also not statistically significant, was that nonphysicians and staff stationed in the medical wards were more likely to default on their PEP treatment. A possible reason for this is that nonphysicians underestimate the need to complete treatment and/or that staff in the medical ward might have underestimated exposure risks compared to those in the surgical ward.

TABLE 1 Examining for Predictors of PEP Default in Bivariate Analysis

NOTE. CI, confidence interval; TDF, tenofovir; ART, antiretroviral treatment.

^a Specifically refer to combination ART that excludes tenofovir but includes a combination of zidovudine, lamivudine, stavudine, efavirenz, and nevirapine.

^b Refers to a nurse, laboratory scientists, health attendants, and students.

This study highlights predictors of PEP default in a tertiary-care hospital in a resource-limited setting. Nontenofovir containing regimen was a statistically significant predictor of PEP default, while 3 pills compared to 2 pills, staff in the medical ward and nonphysician status, though not statistically significant, also predicted default PEP treatment. However, the role of pill burden, category, and station of staff as predictors of PEP default should be further investigated in a multicenter prospective design using a larger sample size. This knowledge will help clinicians understand how to improve PEP uptake to prevent new HIV infections.