Poor adherence to HIV PEP after sexual assault

Michael Carter
Published: 16 March 2012

Adherence to HIV post-exposure prophylaxis (PEP) among victims of sexual assault is poor, according to the results of a meta-analysis and systematic literature review published in Sexually Transmitted Infections.

Approximately 40% of patients did not return for follow-up appointments. The investigators also found that few studies examined the efficacy of adherence support.

“Our review confirms an overall low rate of adherence to PEP among victims of sexual assault with a considerable variation in rates of adherence and defaulting across a broad range of settings,” write the authors. “Low adherence is a concern as it is associated with a risk of reduced efficacy and increased risk of resistance to antiretroviral therapy.”

Treatment with a short course (28 days) of combination antiretroviral viral therapy can reduce the risk of infection with HIV after possible sexual exposure to the virus. In many settings, PEP is offered to the victims of sexual assault. The therapy has the potential to make a significant impact on HIV incidence. In Kenya, which has a generalised HIV epidemic, a quarter of women report being raped and about 4% of HIV infections in adolescents have been attributed to sexual assault.

Adherence to PEP can be challenging, and the results of studies conducted in a variety of settings have suggested that completion rates of the treatment following sexual assault are lower following sexual assault compared with possible exposure after consensual sex. Factors associated with poor adherence could include stigma, trauma following rape and assault, treatment side-effects and lack of support.

However, rates of adherence to PEP following sexual exposure and the factors affecting them are poorly understood. Therefore an international team of investigators conducted a literature review and meta-analysis to establish a better appreciation of these issues.

A total of seven electronic databases were screened by the investigators in June 2011.They identified a total of 24 studies. Most were observational and retrospective. Only three assessed interventions to improve adherence. The overall standard of the studies was poor, and there was no consistency in assessing adherence

Two studies assessed adherence through pill count, seven via patient self-report, and two by pharmacy visit. The other studies did not state how adherence was assessed.

Overall rates of adherence ranged from 12% to 74%, with an overall pooled average of 40%. Adherence appeared to be higher in resource-limited settings than in industrialised countries (53% vs. 33%).

A total of 19 studies reported on the patients who defaulted from PEP (usually defined as failure to return for follow-up appointments). The proportion ranged from 3% to 76%, with an average of 41%.

Refusal rates ranged from 0.09% to 72% (average 29%). The proportion of patients who did not attend for follow-up appointments was between 3% and 65%, with an overall pooled proportion of 33%.

Five studies reported on the impact of side-effects on adherence. Three found a relationship between poorer adherence and the presence of side-effects.

Three studies examined interventions to improve adherence. One found that the introduction of nurse-centred post-rape care increased self-reported rates of adherence compared to the previous model of care. Moreover, the patients’ understanding of therapy was also improved.

“Future research should be directed to assess reasons for poor adherence and therefore potential interventions that could address these issues and improve adherence to PEP,” conclude the authors.


Chacko L et al. Adherence to HIV post-exposure prophylaxis in victims of sexual assault: a systematic review and meta-analysis. Sex Transm Infect, online edition. DOI: 10.1136/sextrans-2011-050371, 2012.

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