Background: Previous investigations suggest an important role of social support in the outcomes of patients treated for ischemic heart disease. The ENRICHD Social Support Instrument (ESSI) is a 7-item self-report survey that assesses social support. Validity and reliability of the ESSI, however, has not been formally tested in patients undergoing percutaneous coronary intervention (PCI).
Methods: The ESSI, along with the Short Form-36 (SF-36), was sequentially administered to a cohort of 271 patients undergoing PCI. The test-retest reliability was examined with an intra-class correlation coefficient by comparing scores among 174 patients who completed both instruments 5 and 6 months after their procedure. Internal reliability was assessed using Cronbach's alpha at the time of patients' baseline procedure. The concurrent validity of the ESSI was assessed by comparing scores between depressed (MHI-5 score < 44) vs. non-depressed patients. The correlation between the ESSI and the SF-36 Social Functioning sub-scale, an accepted measure of social functioning, was also examined.
Results: Test-retest reliability showed no significant differences in mean scores among ESSI questionnaires administered 1 month apart (27.8+/-1.4 vs 27.8+/-1.5, p = 0.98). The intra-class correlation coefficient was 0.94 and Cronbach's alpha was 0.88. Mean ESSI scores were significantly lower among depressed vs. non-depressed patients (24.6+/-1.7 vs 27+/-1.4, p < 0.018) and a positive albeit modest correlation with social functioning was seen (r = 0.19, p = 0.002).
Conclusion: The ESSI appears to be a valid and reliable measure of social support in patients undergoing treatment for coronary artery disease. It may prove to be a valuable method of controlling for patient variability in outcomes studies where the outcomes are related to patients' social support.