2019 HSR&D/QUERI National Conference

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

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.

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.

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.

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

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.