Dear Editor,
We wish to provide five corrections and clarifications regarding our Canadian guideline on HIV pre-exposure prophylaxis and nonoccupational post-exposure prophylaxis (PrEP and nPEP), published in CMAJ in November 2017.1
Definition of undetectable viral load: HIV-positive persons with undetectable viral load and no sexually transmitted infections are classified as having negligible/no risk of transmissible HIV. The Panel used the definition of <40 copies/mL for undetectable viral load because this is the most commonly used definition in clinical care in Canada. However, the Panel recognizes that studies on this topic have used different definitions for "undetectable", most often <200 copies/mL (reviewed on page 6 of Appendix 1).
Indications for PrEP in heterosexual individuals: In the accompanying full guideline (online Appendix 1), the part of recommendation #2 (page 9) indicating that “PrEP may be considered for the HIV-negative partner in heterosexual serodiscordant relationships reporting condomless vaginal or anal sex, where the HIV-positive partner has a non-negligible risk of having transmissible HIV” should be Grade 2B (weak recommendation, moderate quality of evidence), as correctly labelled in the published article, rather than Grade 1B.
Exposures involving compromised skin: Blood or other potentially infectious body fluids contacting compromised skin is classified as a low risk exposure type. Although Table 4 indicates that nPEP is usually not required for low-risk exposures, the Panel wishes to clarify that nPEP may be considered on a case-by-case basis if the likelihood that the source person has transmissible HIV is substantial or low.
Timing of repeat HIV testing when acute HIV is suspected: In the context of nPEP, when initial HIV testing is negative but acute HIV infection is clinically suspected in either the source or exposed person, the suggested timing for repeat 4th generation HIV testing listed in Box 5 (article), Box 5.1 (Appendix 1) and Supplementary Table 3 (Appendix 1), is 7-21 days later, as described elsewhere in the documents when acute HIV infection is discussed, rather than 7-14 days later. The Panel emphasizes that the optimal timing for repeat testing must take into consideration the timing of exposure and the window period of the relevant test.