In sub-Saharan Africa (SSA), home to >70% of the global HIV disease burden,1 as many as 1 in 3 patients develop virologic failure within 2 years of initiating antiretroviral therapy (ART).2 The World Health Organization (WHO) definition of virologic failure requires 2 consecutive HIV-1 RNA levels >1000 copies/mL measured 3 months apart after a minimum 6 months of ART, with adherence support in the interim.3 Individuals with HIV RNA <1000 copies/mL do not enter the WHO algorithm for treatment failure, and therefore do not meet criteria for potentially switching to second-line therapy. Guidelines also do not include recommendations for the use of resistance testing to guide therapy. Using data from a large cohort of individuals on ART in rural Uganda, we evaluated 2 key aspects of the WHO guidelines for managing virologic failure: (1) the threshold for defining virologic failure and (2) the relationship between level of adherence after detectable viremia and odds of resuppression.
We analyzed data from the Uganda AIDS Rural Treatment Outcomes (UARTO) study (NCT01596322), a prospective cohort study in southwestern Uganda from 2005 to 2015, extensively described previously.4,5 The UARTO study enrolled participants at the time of ART initiation at the Mbarara Regional Referral Hospital (MRRH) Immune Suppression Syndrome (ISS) Clinic, a government-run facility that provides ART at no cost to patients. Eligible participants for inclusion in the cohort were older than 18 and lived within 60 kilometers of the clinic.
Study Design and Study Population
For this analysis, we included study participants who were (1) ART-naive, (2) had detectable HIV RNA >400 copies/mL after a minimum of 4 months of ART or after a previously undetectable HIV RNA, and (3) did not change regimens before their next HIV RNA measurement. HIV RNA was measured quarterly as part of study protocol, but results were not available to providers in real time. Participants were excluded from the analysis if adherence data were unavailable or if the time between viral load measurements was less than 30 days.
Adherence to ART was objectively monitored using electronic pillbox systems. MEMSCap (WestRock, Switzerland), used from 2005 to 2011, recorded pill bottle openings electronically, and data were downloaded at each study visit.6,7 Wisepill (Wisepill Technologies, South Africa), used from 2010 to 2015, transmitted pill bottle opening events over cellular networks to provide real-time adherence data.8
Our primary outcome of interest was virologic resuppression (<400 copies/mL) at the next measurement after an initially detectable HIV RNA. HIV RNA was measured using Roche Amplicor HIV-1 Monitor Test [lower limit of detection 400 copies/mL] from 2005 to 2012 and Cobas Taqman Test (lower limit of detection 20 copies/mL) from 2012 to 2015. We used a threshold of 400 copies/mL to consistently define the outcome throughout the study period, during which the limits of detection changed. Primary predictors of interest were (1) magnitude of initial detectable HIV RNA, categorized as detectable <500; 500–1000; 1000–10,000; 10,000 to 100,000; and >100,000 copies/mL and (2) average adherence, categorized as <70%, 70%–90%, and >90%, based on previous work relating those categories with risk of subsequent viremia.9
We used χ2 tests to evaluate crude relationships between (1) level of HIV viremia and viral resuppression and (2) average ART adherence and viral resuppression, stratified by level of HIV viremia. We then fit logistic regression models with robust standard errors to account for repeated episodes of detectable viremia within participants. We estimated the significance of an interaction term to test associations between adherence, level of initial HIV viremia, and odds of resuppression. We also performed a secondary analysis in which viral resuppression was redefined as a second viral load <1000 copies/mL, in fitting with the current WHO guidelines. Finally, we performed sensitivity analyses, in which we excluded repeat episodes of detectable viremia that occurred for any single individual. Statistical analysis was conducted with Stata 14 (Stata Corp., College Station, TX).
This study was approved by Institutional Review Boards at Partners Healthcare, University of California San Francisco, Mbarara University of Science and Technology, and Uganda National Council for Science and Technology. All participants provided signed written consent.
We evaluated data from 107 participants (14% of total cohort) who met the inclusion criteria for this analysis and contributed 139 unique treatment failure events from 2006 to 2013. Of these, 64% were women. At the time of first detectable viremia, median age was 36, median duration of ART was 0.9 years (interquartile range 0.7–2.1 years), and most participants were taking lamivudine/zidovudine/nevirapine (53%), lamivudine/stavudine/nevirapine (25%), or lamivudine/zidovudine/efavirenz (13%) (Table 1).
Participants with HIV RNA <1000 copies/mL were significantly more likely to resuppress at next measurement as compared to participants with HIV RNA >1000 copies/mL (88% versus 42%, P < 0.001, Fig. 1A). There was no significant difference in odds of resuppression between those with HIV RNA 500–1000 copies/mL compared with HIV RNA <500 copies/mL (odds ratio 0.5; 95% confidence interval: 0.10 to 2.60; P = 0.410).
For events with initial HIV RNA <1000 copies/mL, average adherence was a significant predictor of resuppression (P = 0.011, Fig. 1B). By contrast, for participants with HIV RNA >1000 copies/mL, average adherence was not associated with resuppression (P = 0.894, Fig. 1B; interaction term P = 0.077). In the secondary analysis in which viral resuppression was redefined as HIV RNA <1000 copies/mL, rather than <400 copies/mL, only 10 events were reclassified, and results remained unchanged. Results were also unchanged in sensitivity analyses when we restricted models to only first episodes of detectable viremia for each participant.
In this analysis, we used data from a longitudinal cohort in rural Uganda including objective adherence monitoring to evaluate the relationships between the level of HIV viremia, ART adherence, and viral resuppression, which are key aspects of the current WHO guidelines. We found that most of those with an HIV RNA <1000 copies/mL (88%) resuppressed at their next HIV RNA measurement, and that adherence after the first episode of failure was a reliable predictor of resuppression. Although low-level viremia is not currently mentioned in most international guidelines, these findings suggest that such individuals should also be considered as candidates for intensified adherence support interventions. By contrast, only 42% of those with HIV RNA >1000 copies/mL resuppressed, and higher levels of adherence did not predict resuppression in this group. Notably, resuppression rates were low even in participants with >90% average adherence, suggesting that adherence support in this group might not be sufficient to optimize rates of virologic suppression. Instead, for those with higher levels of viremia at failure, resistance testing, where feasible, may improve selection of participants for second-line therapy versus adherence support interventions.
Although low-level viremia has been associated with future virologic failure10–12 and resistance has been detected in those with HIV RNA <1000 copies/mL,13,14 our data support the current WHO recommended threshold of 1000 copies/mL to define treatment failure. The great majority of patients below this threshold resuppressed at the next measurement. Moreover, a threshold of 1000 copies/mL has important advantages for risk of HIV transmission15–17 and accuracy of dried blood spot testing, a commonly used testing modality in the region.18–21 However, our study was relatively short in observation, and it will be important for future studies to consider long-term outcomes and rates of drug resistance for patients with low-level viremia in SSA to ensure that they can achieve durable suppression on first-line regimens.
Importantly, we found low rates of resuppression (42%) for those with higher HIV RNA at the time of failure and no association between level of adherence and resuppression. These findings are in contrast to pooled estimates in a systematic review by Bonner et al,22 which is cited by WHO as evidence to support current requirements for 2 consecutive HIV RNA results >1000 copies/mL to define virologic failure, with adherence support in the interim.3 That review reported that 70% of patients with elevated HIV RNA resuppress after an adherence intervention.22 However, the review included diverse populations from multiple settings, both adults and children, varying ART regimens (including protease inhibitors), and most notably, robust adherence interventions such as educational programs, support groups, dosing diaries, and home visits, which may be feasible in some settings in SSA but are not widely available. Moreover, even where these strategies are available, they remain largely unproven in practice.23,24
By contrast, several other studies from SSA have demonstrated that most (60%–90%) patients with virologic failure on first-line regimens have clinically significant drug resistance mutations at the time of failure.25–28 Our results would support these studies, as we found most patients do not resuppress after an HIV RNA >1000 copies/mL, including those with >90% average adherence (Fig. 1B). Similarly, a recent study in Swaziland failed to find improved rates of resuppression with augmented adherence support.24 Taken together, this body of evidence suggests that resistance might be a primary driver of treatment failure for an important majority of patients with high-level viremia in the region. A clinical trial is currently underway to evaluate the feasibility, efficacy, and cost-effectiveness of resistance testing after a detectable HIV RNA with high-level viremia (NIH AI124718; NCT02787499).
Our results should be interpreted with consideration of our single-site study design and sample size. Furthermore, we acknowledge that our study does not provide an exact evaluation of the WHO algorithm, given that participants were included after 4 months of ART and that viral suppression in our study was defined as 400 copies/mL, as opposed to 1000 copies/mL in the guidelines. We are also unable to fully evaluate the efficacy of WHO guidelines in this study, given that HIV RNA testing was not performed as part of routine clinical care and was not available to guide care plans or changes in therapy. We do not have paired resistance data available to assess its impact on our findings, although this is planned for future analyses. Our estimates could be biased by misestimation of ART adherence. However, we have previously demonstrated very strong associations between electronically captured adherence, drug levels, and virologic failure in our study.29,30 Moreover, the only way in which misestimation of adherence would meaningfully affect our estimates would be if there was a differential practice in use (or misuse) of adherence monitors between those with high and low viral loads, which we believe to be unlikely. Approximately 75% of evaluated events in this analysis were observed on nevirapine-based regimens, which remain in wide use but are no longer a recommended first-line option in SSA. Similarly, 25% of participants were on stavudine, which was no longer recommended as part of first-line ART at the time the 2013 WHO guidelines were published. Because we were not powered to detect differences by regimen, future studies should attempt to do so.
In conclusion, our data support the recommended WHO HIV RNA threshold of 1000 copies/mL to determine virologic failure. However, although patients with low-level viremia are not discussed in WHO guidelines for management of virologic failure, we offer evidence that adherence support might particularly benefit this group. In addition, because most patients do not resuppress after failure with HIV RNA viremia above 1000 copies/mL and because adherence does not predict their resuppression, HIV drug resistance should be considered as an etiology for treatment failure so as to optimize the selection of immediate second-line therapy versus adherence support in this population. To achieve global targets to maintain viral suppression in 90% of those on ART, feasibility of resistance testing in SSA should be further evaluated.
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