Chemical Adherence Testing for Assessing Adherence to Antihypertensive Medications: A Systematic Review and Meta-Analysis of Prevalence of Nonadherence.

Nonadherence to antihypertensive medications is highly prevalent, driving cardiovascular risk. Chemical adherence testing (CAT) can detect the presence of medications or their metabolites in bodily fluid, though it is unclear if its use to date has been equitable. This review aimed to identify the demographics with hypertension in which CAT has been used previously, and to estimate the resulting prevalence of nonadherence. Multiple databases were searched from 2013 to February 2024. We included any published paper that reported CAT data in people with hypertension. Extracted data included: study design and setting, hypertension definition and type, participant sociodemographic factors, and prevalence of nonadherence. Data were synthesized using a random effects meta-analysis with meta-regression, or narrative synthesis. Seventy eligible papers were identified. Many papers did not present key participant sociodemographic data, including ethnicity or socioeconomic, educational or disability status. Most studies were completed in tertiary care settings, and in primarily White patients with apparent treatment-resistant hypertension. The estimated pooled prevalence of complete medication nonadherence was 15.0%, increasing to 33.0% when estimating any kind of nonadherence; heterogeneity was high in both analyses (I of 94.6% and 95.6%, respectively). Nonadherent patients had higher blood pressure and were prescribed more antihypertensive medications, whilst participant age showed an inverse relationship with prevalence of nonadherence. Key relevant sociodemographic factors were often not reported, limiting the understanding of CAT use in diverse populations. In order to support behavior change interventions to address medication nonadherence in underserved groups, future research should recruit diverse populations to inform equitable implementation. International Prospective Register of Systematic Reviews CRD42024505602.