1155 — Can this patient follow the treatment plan? Validity and Reliability of a Self-Efficacy Instrument for Hypertension Treatment Adherence in Veterans

Lead/Presenter: Sundar Natarajan, 
All Authors: Natarajan S (VA New York Harbor Healthcare System), Maria A Rodriguez, PhD, VA New York Harbor Healthcare System Jennifer P Friedberg, PhD, VA New York Harbor Healthcare System John P. Allegrante, PhD, Teachers College-Columbia University

Objectives:
Self-efficacy strongly influences ability to achieve treatment goals. Our goal was to assess the validity and reliability of a self-efficacy instrument designed to assess confidence to follow diet, exercise, and medication to treat hypertension among Veterans.

Methods:
This study was embedded within a 6-month randomized clinical trial (RCT) which demonstrated that a tailored, stage-matched intervention was more effective at improving hypertension control than usual care among veterans (n = 533) with uncontrolled hypertension. We modified questions self-efficacy short assessment scales to directly address hypertension. The final 17-item instrument comprised three subscales that assessed diet self-efficacy (DSE), exercise self-efficacy (ESE), and medication self-efficacy (MSE). To determine validity and reliability, we assessed internal consistency using Cronbach's alpha coefficients, evaluated convergent and discriminant validity using Spearman's rho coefficients, test-retest reliability using correlation coefficients and conducted exploratory factor analysis.

Results:
The instrument demonstrated strong internal consistency with high Cronbach's ? values for DSE (.81), ESE (.82), and MSE (.74). The instrument possessed good convergent validity: DSE was compared to baseline DASH score (from Willett food frequency questionnaires) for a Spearman coefficient of 0.17 (p-value = 0.0004); ESE was compared to baseline aerobic exercise in hours per week (from the Sallis 7-day physical activity recall) for a Spearman coefficient of 0.27 (p-value < 0.0001). MSE was compared to baseline medication adherence as determined from the 4-item Morisky Scale for a Spearman coefficient of 0.24 (p-value < 0.0001). The instrument had good discriminant validity; serum sodium was compared to DSE, ESE, and MSE for Spearman coefficients of -0.001 (p-value = 0.99), 0.008 (p-value = 0.86), and 0.016 (p-value = 0.90) respectively. Test-retest reliability was 0.58 (p-value < 0.0001) for DSE, 0.57 (p-value < 0.0001) for ESE and 0.49 (p-value < 0.0001) for MSE. Factor analysis and the scree plot demonstrated three distinct factors, corresponding to the three subscales in the self-efficacy instrument.

Implications:
A self-efficacy instrument containing diet, exercise, and medication adherence subscales was valid and reliable in Veterans with uncontrolled hypertension.

Impacts:
Future clinical and research programs among Veterans with hypertension can incorporate this instrument to measure self-efficacy for making behavioral changes to follow treatment and can intervene accordingly for those with low self-efficacy.