Eligibility Criteria
Age ≥65 yReceiving hydrochlorothiazide at 25 or 50 mg daily (within 25% from the targeted values)Systolic blood pressure ≥120 mm Hg (most recent record within 2 y of data extraction date)In the past 90 d, no record of systolic blood pressure <120 mm HgIn the past 90 d, no record of potassium <3.1 or <3.5 mEq/L (if receiving digoxin medication)In the past 90 d, no record of sodium level <130 mEq/L
To convert potassium to millimoles per liter, multiply by 1.0; sodium to millimoles per liter, multiply by 1.0.PCC approval was required before patient randomization. An electronic order was sent to request a PCC’s assent for a particular patient to undergo study randomization. The PCC provided an electronic signature (using the physician order entry feature) to confirm approval. The corresponding electronic approval was detected from a patient’s EHR. Medical record review was performed by study nurses to verify patient eligibility. Once confirmed, electronic randomization was performed.For patients who were randomized to continue with hydrochlorothiazide, no further action was needed from their PCC. However, de facto PCC approvals were needed if the patients were randomized to switch from hydrochlorothiazide to chlorthalidone (ie, changing medication from usual care practice). An EHR alert notification was sent by the study nurse, requesting the PCC to discontinue hydrochlorothiazide and prescribe chlorthalidone. PCC approval was provided as an electronic signature, which was detected directly from CDW. The release of chlorthalidone medication was subsequently confirmed by EHR data generated from the VA outpatient pharmacy services. Notification letters were sent to patients by the central mailing center when a PCC declined study randomization, study nurses determined patients were ineligible based on EHR review, or a PCC approved study randomization and signed the corresponding prescription orders.A web-based software application (ProjectFlow) was applied to support custom research data collection,Electronic operations were standardized across the VA primary care networks (