PrEP Nonadherence, White Coat Dosing, and HIV Risk Among a Cohort of MSM

Urine tenofovir testing for real-time PrEP adherence feedback: a qualitative study involving transgender women in Uganda

INTRODUCTION

Adherence counselling with point-of-care (POC) drug-level feedback using a novel tenofovir assay may support pre-exposure prophylaxis (PrEP) adherence; however, perceptions of urine testing and its impact on adherence are not well studied. We qualitatively examined how POC tenofovir testing was experienced by transgender women (TGW) in Uganda.

METHODS

Within a cluster randomized trial of peer-delivered HIV self-testing, self-sampling for sexually transmitted infections and PrEP among HIV-negative TGW showing overall low PrEP prevention-effective adherence (NCT04328025), we conducted a nested qualitative sub-study of the urine POC assay among a random sample of 30 TGW (August 2021-February 2022). TGW interviews explored: (1) experiences with POC urine tenofovir testing and (2) perceptions of PrEP adherence counselling with drug-level feedback. We used an inductive content analytic approach for analysis.

RESULTS

Median age was 21 years (interquartile range 20-24), and 70% engaged in sex work. Four content categories describe how TGW experienced POC urine tenofovir testing: (1) Urine tenofovir testing was initially met with scepticism: Testing urine to detect PrEP initially induced anxiety, with some perceptions of being intrusive and unwarranted. With counselling, however, participants found POC testing acceptable and beneficial. (2) Alignment of urine test results and adherence behaviours: Drug-level feedback aligned with what TGW knew about their adherence. Concurrence between pill taking and tenofovir detection in urine reinforced confidence in test accuracy. (3) Interpretation of urine tenofovir results: TGW familiar with the interpretation of oral-fluid HIV self-tests knew that two lines on the test device signified positivity (presence of HIV). However, two lines on the urine test strip indicated a positive result for non-adherence (absence of tenofovir), causing confusion. Research nurses explained the difference in test interpretation to participants' satisfaction. (4) White coat dosing: Some TGW deliberately chose not to attend scheduled clinic appointments to avoid detecting their PrEP non-adherence during urine testing. They restarted PrEP before returning to clinic, a behaviour called "white coat dosing."

CONCLUSIONS

Incorporating POC urine testing into routine PrEP adherence counselling was acceptable and potentially beneficial for TGW but required attention to context. Additional research is needed to identify effective strategies for optimizing adherence monitoring and counselling for this population.

Point-of-care urine tenofovir monitoring of adherence to drive interventions for HIV treatment and prevention

INTRODUCTION

Although effective antiretroviral and pre-exposure prophylaxis/PrEP regimens are available globally, adherence challenges persist. Objective measures of adherence can both measure adherence accurately and can be used to drive interventions. The first point-of-care pharmacologic adherence measure, urine tenofovir testing using a lateral flow assay, is now available.

AREAS COVERED

This review examines the ability of pharmacologic metrics of adherence to predict HIV and PrEP clinical outcomes and the past use of pharmacologic metrics of adherence as tools to drive adherence interventions. The success of preliminary studies using point-of-care adherence metrics to guide interventions is then discussed.

EXPERT OPINION

Large randomized clinical trials are now needed to test the impact of point-of-care adherence interventions on HIV and PrEP clinical outcomes, given promising results of the pilot studies summarized here. Hybrid implementation-effectiveness studies will be needed to examine optimal approaches to incorporating point-of-care testing into routine clinical care delivery, including in guiding resistance testing, adherence counseling, and delivery of other evidence-based adherence interventions. Given the ability of point-of-care tenofovir testing to be implemented in settings where viral load testing is not available, and at more frequent intervals due to its low cost, urine-based tenofovir assays have the potential to be highly scalable in diverse clinical settings.

Randomized controlled trials of biomarker targets

INTRODUCTION

Randomized controlled trials are used to estimate the causal effect of a treatment on a health outcome of interest in a patient population. Often the specified treatment in a randomized controlled trial is a medical intervention-such as a drug or procedure-experienced directly by the patient. Sometimes the "treatment" in a randomized controlled trial is a target-such as a goal biomarker measurement-that the patient's physician attempts to reach using available medications or procedures. Large randomized controlled trials of biomarker targets are common in clinical research, and trials have been conducted to compare targets in the management of hypertension, diabetes, anemia, and acute respiratory distress syndrome. However, different randomized controlled trials intended to evaluate the same biomarker targets have produced conflicting recommendations, and meta-analyses that aggregate results of trials of biomarker targets have been inconclusive.

METHODS

We use causal reasoning to explain why randomized controlled trials of biomarker targets can arrive at conflicting or misleading conclusions. We describe four key threats to the validity of trials of targets: (1) intention-to-treat analysis can be misleading when a direct effect of target assignment on the outcome exists due to lack of blinding; (2) incomparability in results across trials of targets; (3) time-varying adaptive treatment strategies; and (4) Goodhart's law, "when a measure becomes a target, it ceases to be a good measure."

RESULTS

We illustrate these findings using evidence from 15 randomized controlled trials of blood pressure targets for management of hypertension. Randomized trials of blood pressure targets exhibit substantial variation in the trial patient populations and antihypertensives used to achieve the blood pressure targets assigned in the trials. The trials did not compare or account for time-varying treatment strategies used to reach the randomized targets. Possible "off-target" effects of antihypertensive medications needed to reach lower blood pressure targets may explain the absence of a clear benefit from intensive blood pressure control.

DISCUSSION

Researchers should critically assess meta-analyses of trials of targets for variation in the types, distributions, and off-target effects of therapies studied. Trial investigators should release detailed information about the biomarker targets compared in new randomized trials, as well as confounders, treatments delivered, and outcomes. New randomized controlled trials should experimentally compare treatment algorithms incorporating biomarkers, rather than targets alone. Causal inference methodology that adjusts for time-varying confounding should be used to compare time-varying treatment strategies in observational settings.

Whitecoat Adherence in Patients With Primary Open-Angle Glaucoma

Purpose

Whitecoat adherence refers to improved medication adherence in the days surrounding clinic visits. This may lead to clinical measures that are not representative of those outside of clinical encounters. In glaucoma, whitecoat adherence to prescribed hypotensive therapy may lead to intraocular pressure readings within the target range, which may impact clinical decision-making. We aimed to quantify and identify factors associated with whitecoat adherence.

Methods

In this cohort study, patients with primary open-angle glaucoma were selected from an ongoing longitudinal NIH-funded study if they used hypotensive eyedrops, had a clinic visit during the parent study, and had adherence data during the 28 days evenly bracketing the clinic visit. Adherence within the implementation phase was measured using Medication Event Monitoring System (MEMS) caps. Wilcoxon tests were used to compare mean adherence between the following periods: Pre14-4 (days 14 to 4 preceding the clinic visit) and Pre3-1 (days 3 to 1 preceding the visit); Post1-3 (days 1 to 3 following the clinic visit) and Post4-14 (days 4 to 14 following the visit). Analyses were performed in the full sample and in patients with optimal (≥80%, n = 49) and suboptimal adherence (<80%, n = 17).

Results

Sixty-six patients were included, of which 51.5% were female. Mean age was 70.8 ± 8.1 years. In the 6 months evenly bracketing the clinic visit, mean and median adherence were 86.3% (standard deviation = 17.7) and 95.6% (interquartile range = 21.2), respectively. Overall, mean adherence increased from Pre14-4 to Pre3-1 (85.5% ± 21.2 to 88.5% ± 23.2, p = 0.01) and decreased from Post1-3 to Post4-14 (87.0 ± 23.9 to 84.9 ± 23.3, p = 0.02). In patients with optimal adherence, adherence increased from Pre14-4 to Pre3-1 (94.0 ± 11.7 to 97.7 ± 7.4, p = 0.001) and from Post1-3 to Post4-14 (95.2 ± 12.0 to 95.4 ± 5.7, p = 0.007). Whitecoat adherence was not observed in patients with suboptimal adherence.

Conclusion

We documented the presence of whitecoat adherence in this cohort. Due to its potential impact on clinical outcomes and decisions, providers should remain vigilant for this phenomenon and prioritize it during patient-provider discussions.