Utilizing quantitative dried blood spot analysis to objectively assess adherence to cardiovascular pharmacotherapy among patients at Kenyatta National Hospital, Nairobi, Kenya

The burden of cardiovascular disease (CVD) is rising in Kenya and non-adherence to cardiovascular pharmacotherapy is a growing global public health issue that leads to treatment failure, an increased risk of cardiac events and poor clinical outcomes. This study assessed adherence to selected cardiovascular therapy medications among CVD patients attending outpatient clinics at Kenyatta National Hospital, Kenya by determining drug concentration(s) in patient dried blood spot (DBS) samples. Patients who had been taking one or more of the five commonly prescribed CVD medications (amlodipine, atenolol, atorvastatin, losartan, and valsartan) for at least six months were enrolled. Each patient completed a short questionnaire about their medication history and then provided a finger-prick blood spot sample from which drug concentrations were determined by liquid chromatography-high resolution mass spectrometry analysis. Two hundred and thirty-nine patients (62.3% female) participated in the study. The median number of medications used by patients was 2 (IQR 75%-25% is 3–1). Less than half (117; 49.0%) of patients were adherent to their prescribed CVD pharmacotherapy. Binary regression analysis revealed a significant correlation between non-adherence and the number of medications in the treatment regimen (Odds Ratio (OR) 1.583; 95%CI: 0.949–2.639; P-value = 0.039) and that gender was not an independent predictor of medication adherence (OR 1.233; 95%CI: 0.730–2.083; P-value = 0.216). Valuable information about adherence to each medication in the patient’s treatment regimen was obtained using quantitative DBS analysis showing that adherence to CVD medications was not uniform. DBS sampling, due its minimally invasive nature, convenience and ease of transport is a useful alternative matrix to monitor adherence to pharmacotherapies objectively, when combined with hyphenated mass spectrometry analytical techniques. This information can provide physicians with an evidence-based novel approach towards personalization and optimization of CVD pharmacotherapy and implementing interventions in the Kenyan population, thereby improving clinical outcomes.