A quasi-experimental test of an intervention to increase the use of thiazide-based treatment regimens for people with hypertension

BACKGROUND: Despite recent high-quality evidence for their cost-effectiveness, thiazides are underused for controlling hypertension. The goal of this study was to design and test a practice-based intervention aimed at increasing the use of thiazide-based antihypertensive regimens. METHODS: This quasi-experimental study was carried out in general medicine ambulatory practices of a large, academically-affiliated Veterans Affairs hospital. The intervention group consisted of the practitioners (13 staff and 215 trainees), nurses, and patients (3,502) of the teaching practice; non-randomized concurrent controls were the practitioners (31 providers) and patients (18,292) of the non-teaching practices. Design of the implementation intervention was based on Rogers' Diffusion of Innovations model. Over 10.5 months, intervention teams met weekly or biweekly and developed and disseminated informational materials among themselves and to trainees, patients, and administrators. These teams also reviewed summary electronic-medical-record data on thiazide use and blood pressure (BP) goal attainment. Outcome measures were the proportion of hypertensive patients prescribed a thiazide-based regimen, and the proportion of hypertensive patients attaining BP goals regardless of regimen. Thirty-three months of time-series data were available; statistical process control charts, change point analyses, and before-after analyses were used to estimate the intervention's effects. RESULTS: Baseline use of thiazides and rates of BP control were higher in the intervention group than controls. During the intervention, thiazide use and BP control increased in both groups, but changes occurred earlier in the intervention group, and primary change points were observed only in the intervention group. Overall, the pre-post intervention difference in proportion of patients prescribed thiazides was greater in intervention patients (0.091 vs. 0.058; p = 0.0092), as was the proportion achieving BP goals (0.092 vs. 0.044; p = 0.0005). At the end of the implementation period, 41.4% of intervention patients were prescribed thiazides vs. 30.6% of controls (p < 0.001); 51.6% of intervention patients had achieved BP goals vs. 44.3% of controls (p < 0.001). CONCLUSION: This multi-faceted intervention appears to have resulted in modest improvements in thiazide prescribing and BP control. The study also demonstrates the value of electronic medical records for implementation research, how Rogers' model can be used to design and launch an implementation strategy, and how all members of a clinical microsystem can be involved in an implementation effort.