Effect of a physician uncertainty reduction intervention on blood pressure in uncontrolled hypertensives--a cluster randomized trial

Abstract

Background: Clinical inertia, provider failure to appropriately intensify treatment, is a major contributor to uncontrolled blood pressure (BP). Some clinical inertia may result from physician uncertainty over the patient's usual BP, adherence, or value of continuing efforts to control BP through lifestyle changes.

Objective: To test the hypothesis that providing physicians with uncertainty reduction tools, including 24-h ambulatory BP monitoring, electronic bottle cap monitoring, and lifestyle assessment and counseling, will lead to improved BP control.

Design: Cluster randomized trial with five intervention clinics (IC) and five usual care clinics (UCC).

Setting: Six public and 4 private primary care clinics.

Participants: A total of 665 patients (63 percent African American) with uncontrolled hypertension (BP ≥140 mmHg/90 mmHg or ≥130/80 mmHg if diabetic).

Interventions: An order form for uncertainty reduction tools was placed in the IC participants' charts before each visit and results fed back to the provider.

Outcome measures: Percent with controlled BP at last visit. Secondary outcome was BP changes from baseline.

Results: Median follow-up time was 24 months. IC physicians intensified treatment in 81% of IC patients compared to 67% in UCC (p < 0.001); 35.0% of IC patients and 31.9% of UCC patients achieved control at the last recorded visit (p > 0.05). Multi-level mixed effects longitudinal regression modeling of SBP and DBP indicated a significant, non-linear slope difference favoring IC (p (time × group interaction) = 0.048 for SBP and p = 0.001 for DBP). The model-predicted difference attributable to intervention was -2.8 mmHg for both SBP and DBP by month 24, and -6.5 mmHg for both SBP and DBP by month 36.

Conclusions: The uncertainty reduction intervention did not achieve the pre-specified dichotomous outcome, but led to lower measured BP in IC patients.

Figure 1

Consort diagram. Patients were included in the analysis until death or censoring at their last recorded visit. Five deaths occurred in intervention patients (1 at 9 months and 4 after >12 months of follow-up), and 8 death occurred in the control group (all after >12 months of follow-up).

Figure 2

Systolic and diastolic blood pressure trend in intervention compared to control clinics. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) trends in intervention and control clinics predicted from the mixed effects models. The SBP prediction equation was: 141.48 + 070 (age) - 1.738 (sex) + 2.540 (black) - 0.658 (follow-up month) + 2.291(group assignment) + 0.020 (follow-up month squared) - 0.005 (follow-up month squared * group assignment). The DBP prediction equation was: 110.03 - 0.393 (age) - 3.786 (sex) + 3.215 (black) - 2.577 (diabetes) - 0.256 (follow-up month) + 0.1.026 (group assignment) + 0.010 (follow-up month squared) - 0.005 (follow-up month squared * group assignment). Education, smoking, and health system were not significant predictors of SBP or DBP change, and were omitted from final models to preserve degrees of freedom. Diabetes was not associated with SBP change. The p-values for (months squared × group) interaction term were 0.048 and 0.001 for the SBP and DPB models, respectively. The model-predicted difference in SBP in the intervention group compared to the control group is -0.749 mmHg at 12 months, -3.00 mmHg at 24 months, and −6.48 mmHg at 36 months. The model predicted difference in DBP in the intervention group compared to the control group is -0.720 mmHg at 12 months, -2.88 mmHg at 24 months, and -6.48 mmHg at 36 months.

Figure 3

Blood pressure trend in patients referred for any uncertainty reduction intervention compared to patients never referred (intervention clinics only). SBP trend in patients referred for any uncertainty reduction intervention compared to patients never referred in the intervention clinics. The mixed effects linear regression coefficient associated with referral was 5.70 ± 1.70 (p < 0.001), and the coefficient for the interaction of referral by follow-up month was -0.21 ± 0.11 (p = 0.048).