We identified 2,019 citations in the PRS database and an additional 30 newly published citations through hand searches in PubMed (Figure 1). We excluded 1448 citations at the title and abstract level and 506 studies at the full-text level. The remaining 95 studies were included in this review (see Supplemental Table 1, Appendix II and Appendix III, Supplemental Digital Content, https://links.lww.com/QAI/B453). Data were collected between 2004 and 2017. Sample sizes of the included studies varied from 12 to 19,587 respondents; this review included a total of 95,854 responses.
Because this review focused on self-reported surveys and none of the included studies validated the participants' PrEP use with medical records, no studies achieved the highest possible score (5 points) for study quality (see Supplemental Table 1, Appendix II, Supplemental Digital Content, https://links.lww.com/QAI/B453). Thirty-three studies scored 4 points, whereas nearly half of the studies (n = 43) scored 3 points. Seventeen studies attained 2 points, and 2 studies garnered only 1 point.
Of the 95 included studies, 89 exclusively focused on one or more key populations. Eighty (84.2%) studies reported the proportion of MSM, whereas 18 (18.9%) studies reported the proportion among non-MSM. This review also included 39 (41.1%) studies which presented data on blacks, 26 (27.4%) studies on Hispanic/Latinos, 19 (20.0%) studies on youth, 19 (20.0%) studies on people in the Southern United States, 9 (9.5%) on transgender women, and 6 (6.3%) studies on PWID. Only 4 studies (4.2%) focused on female members of one of the groups women identified in national HIV goals (n = 2, 2.1%) or on women in general (n = 2, 2.1%).
Proportions of Self-reported PrEP use Overall and by Year
The unstratified overall average proportion of reported PrEP use across all years and populations was 5.4% (95% CI: 4.6 to 6.3, k = 95, I2 = 97%). Because the tau was calculated each year separately, the stratified overall proportion from a random-effects model was 2.9% (95% CI: 1.7 to 5.0, k = 95, I2 = 97%) (Figure 2). Overall proportions reporting PrEP use each year in 2004–2017 were as follows: 3.0%, 0.3%, 2.3%, 2.0%, 1.0%, 2.3%, 0.7%, 0.9%, 3.0%, 2.7%, 3.2%, 9.5%, 11.6%, and 15.8%, respectively; note some estimates are from single studies.
Forest plot of pooled proportions of self-reported PrEP use stratified by year (N = 95). ◊:pooled year estimate, ♦:pooled overall estimate. *Online publication year.
Proportions of Self-reported PrEP use in Recent Years (2015–2017)
In terms of PrEP use in recent years (2015–2017), the overall proportion was 11.3% (95% CI: 9.9 to 12.9, k = 46, I2 = 96%) (Table 1). Within key populations, MSM reported the highest proportion of using PrEP (13.9%, 95% CI: 8.8 to 21.1, k = 39, I2 = 96%) followed by Hispanic/Latinos (11.5%, 95% CI: 7.1 to 18.1, k = 12, I2 = 95%), transgender women (11.2%, 95% CI: 5.8 to 20.6, k = 5, I2 = 73%), blacks (9.9%, 95% CI: 8.3 to 11.8, k = 18, I2 = 96%), people in the Southern United States (9.9%, 95% CI: 4.7 to 19.7, k = 8, I2 = 94%), youth (7.3%, 95% CI: 4.7 to 11.2, k = 8, I2 = 92%), and PWID (3.7%, 95% CI: 0.8 to 16.1, k = 3, I2 = 73%).
Among subgroups of non-MSM (overall proportion: 5.3%, 95% CI: 3.7 to 7.5, k = 11, I2 = 73%), the highest proportion of PrEP use was observed among Hispanic/Latino non-MSM (12.9%, 95% CI: 5.5 to 27.3, k = 2, I2 = 31%), followed by blacks (8.8%, 95% CI: 4.1 to 17.9, k = 2, I2 = 78%), youth (6.4%, 95% CI: 3.7 to 10.8, k = 2, I2 = 31%), non-MSM in the Southern United States (4.8%, 95% CI: 2.4 to 9.2, k = 1, I2 = n/a), and PWID (1.6%, 95% CI: 0.4 to 6.2, k = 2, I2 = 0%).
Nonoverlapping 95% CI was an indication of some significant differences between strata. These included a lower prevalence of PrEP use among non-MSM compared with black MSM; non-MSM living in the Southern United States compared with MSM; and non-MSM PWID compared with MSM, Hispanic/Latino MSM, or black MSM.
Moreover, the odds of reporting ever PrEP use were twice (aOR = 2.07, 95% CI: 1.27 to 3.38) as high among MSM compared with non-MSM after adjusting for the year between 2015 and 2017. Hispanic/Latinos were the only strata where the non-MSM population reported a higher proportion of PrEP use than the combined group including both MSM and non-MSM.
Growth Rates of PrEP use
The overall growth rate significantly increased both within the preguideline era (in/before 2014, OR = 1.11/year, 95% CI: 1.01 to 1.21) and the postguideline era (after 2014 OR = 1.34/year, 95% CI: 1.09 to 1.64); the growth rate in the postguideline era was larger but not statistically significant (Figure 3).
Growth rate of proportion of self-reported PrEP use within both pre-CDC PrEP clinical guideline era (2004–2014) and postguideline era (2015–2017) periods among US study participants.
The proportion of PrEP use grew significantly during the preguideline era among all key populations except among transgender women (OR = 0.29/year, 95% CI: 0.05 to 1.67) and people in the Southern United States (OR = 0.99/year, 95% CI: 0.85 to 1.15). Because of the limited number of studies, we were not able to calculate a growth rate neither among PWID nor among any of the non-MSM subgroups.
In the postguideline era, the largest point estimate for the growth rate was among Hispanic/Latinos (OR = 1.59/year, 95% CI: 0.62 to 4.08); however, this increase was not significant. Among significant increases during the postguideline era, the largest point estimate was among MSM (OR = 1.53/year, 95% CI: 1.21 to 1.93) and then followed by blacks (OR = 1.44/year, 95% CI: 1.13 to 1.83). The proportion was stable among transgender women (OR = 1.02/year, 95% CI: 0.16 to 6.37), whereas the proportion did not demonstrate growth among people in the Southern United States (OR = 0.94/year, 95% CI: 0.29 to 3.18). Youth significantly improved PrEP use over time in the preguideline era (in/before 2014) (OR = 1.48/year, 95% CI: 1.21 to 1.80), but in the postguideline era (after 2014), the proportion of use (OR = 0.82/year, 95% CI: 0.43 to 1.55) did not demonstrate growth.
Overall heterogeneity and heterogeneity among strata were as high as 97%. We were able to reduce some heterogeneity during various subgroup analyses, but the heterogeneity remained high for some strata—particularly for 2015–2017 and people in the Southern United States (see Supplemental Table 2, Appendix II, Supplemental Digital Content, https://links.lww.com/QAI/B453).
The proportion of PrEP use after excluding studies reporting zero proportion (3.3%, 95% CI: 2.0 to 5.5, k = 83, I2 = 97%) did not differ much from a model that included all studies (2.9%, 95% CI: 1.7 to 5.0, k = 95, I2 = 97%). Our estimated proportions were stable with the continuity correction.
Differences among proportions reporting ever, current, and past 6-month PrEP use were similar for overall, MSM, and non-MSM (see Supplemental Table 3, Appendix II, Supplemental Digital Content, https://links.lww.com/QAI/B453). Moreover, logistic regression excluding past 12-month use showed that the difference in proportions between MSM and non-MSM in recent years after accounting for years of study remained significant (aOR = 2.34, 95% CI: 1.63 to 3.50). These analyses suggest our findings were reliable, although the review included proportions of lifetime use and other recall periods.
Finally, we assessed biases caused by overlap between key populations (eg, black MSM and Hispanic/Latinos in the Southern United States). The proportions of PrEP use among MSM subgroup strata (4.7% for black MSM, 4.4% for Hispanic/Latinos MSM, 2.0% for MSM youth, and 4.0% for MSM in the Southern United States) did not differ much from proportions that included both MSM and non-MSM studies (4.4%, 4.5%, 2.3%, 4.1%, respectively) except PWID (6.2% for MSM and 2.1% for MSM and non-MSM). Therefore, our strategy to separate out non-MSM and report proportions for non-MSM subgroups (but not for MSM subgroups) seems acceptable. Because of the limited number of studies, we were not able to compare other key population subgroups (eg, black vs black in the Southern United States) and assess those biases.
J Acquir Immune Defic Syndr. 2020;84(4):379-386. © 2020 Lippincott Williams & Wilkins