Mid America Heart Institute at St Lukes Hospital, Kansas City, MO, USA
University of Missouri, Kansas City, MO, USA
Abstract
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.
Background
Social support is broadly defined as the existence or availability of people on whom one can rely; people who let one know that they are cared about, valued, and loved
The ESSI has demonstrated acceptable internal consistency and has shown to correlate positively with other social support instruments and negatively with measures of depression
Methods
Subjects and procedures
Participants in this study were from a consecutive cohort of PCI patients participating in the Post-revascularization REcovery StudieS (PRESS) at the Mid-America Heart Institute. The process of patient recruitment, mechanism, success and potential selection biases of baseline health status data collection have been previously described
Instruments
ENRICHD Social Support Instrument (ESSI)
As noted previously, the ESSI is a seven-item, self-report measure used in the ENRICHD trial
SF-36 Mental Health Index and Social Functioning subscale
The SF-36 is a well-known and widely used generic measure of health status. The 36 items cover eight domains including: physical functioning, social functioning, role-physical, role-emotional, mental health, vitality, bodily pain, and general health
Seattle Angina Questionnaire (SAQ) – Angina Frequency and disease-specific Quality of Life
The SAQ is a valid, reliable and responsive disease-specific measure of health status for patients with coronary disease
Statistical analysis
Determining reliability
The internal consistency of the ESSI was calculated using Cronbach's α, which measures the dispersion of different items within a single domain
Determining validity
In the absence of a "gold standard" measure of social support, several constructs were examined to support the validity of the ESSI. We expected that ESSI scores among depressed patients would be lower than non-depressed patients. To define depression, we used the SF-36 MHI score where those patients with scores less than 44 were classified as depressed. To quantitatively assess construct validity, independent sample t-tests of baseline mean ESSI scores were compared among depressed versus non-depressed patients.
Concurrent and predictive validity were examined by calculating the correlation coefficient between the ESSI total score and the SF-36 Social Functioning subscale, the SF-36 Physical and Mental Component Scores, and the SAQ-QOL scale at baseline and 6-months post-revascularization. We anticipated positive associations between social support and social functioning, general, and disease-specific QOL at both time points.
Results
Patient demographics
The study population consisted of 271 patients ranging in age from 37 to 87 years old who underwent PCI to treat ischemic coronary artery disease. The mean patient age was 64.1 years old (SD = 11.2). The population consisted of 32.5% women and 5.9% minorities. Seventy-four percent (74 %) of the patients reported being married. The mean level of education was 12.4 years (SD = 2.0) with 72% of the cohort reported attending some college or vocational school. On average, patients were able to complete the ESSI in 2–3 minutes. Furthermore, the data collectors reported no complaints from patients about completing the instrument.
Reliability
Internal consistency for the ESSI, using Cronbach's α, was 0.88. The inter-item correlations were examined, with significant associations being found between all items and item-total score (p < 0.001). However, question 7 (patient's marital status) consistently had the lowest correlation with the other ESSI items and total score. These results are presented in Table
ESSI inter-item correlations
ESSI Q1
ESSI Q2
ESSI Q3
ESSI Q4
ESSI Q5
ESSI Q6
ESSI Q7
ESSI Total
ESSI Q1
1.0
0.78
0.63
0.47
0.70
0.65
0.26
0.84
ESSI Q2
1.0
0.56
0.41
0.70
0.57
0.18*
0.80
ESSI Q3
1.0
0.46
0.65
0.65
0.37
0.79
ESSI Q4
1.0
0.49
0.48
0.42
0.74
ESSI Q5
1.0
0.76
0.28
0.87
ESSI Q6
1.0
0.25
0.83
ESSI Q7
1.0
0.38
ESSI Total
1.0
All ESSI inter-item correlations p < 0.001, except * p = 0.004.
Test-retest analysis was used to compare mean scores of ESSIs administered at months 5 and 6 after PCI. These time points were selected because they were thought to represent post-procedural periods of relative medical stability. The mean score at month 5 was 28.5 ± 5.6 (M ± SD) and month 6 was 28.5 ± 5.8 (p = 0.98), indicating no significant differences in ESSI scores. The intra-class correlation coefficient was 0.94, reflecting excellent reproducibility.
Concurrent and predictive validity
At baseline, the mean ESSI score among depressed patients was 22.8 ± 4.6 while the non-depressed group mean score was 26 ± 4.3 (p < 0.001). Similarly, patients living alone had significantly lower scores (16 ± 5.1) vs. patients living with someone (20 ± 3.8; p < 0.001). The SF-36 Social Functioning subscale showed a statistically significant albeit modest correlation with the ESSI (r = 0.19, p = 0.002).
Concurrent and predictive validity also was assessed by examining the correlations between the ESSI total score and the SF-36 Social Functioning, Mental Health Index, Mental Component, and Physical Component scales and the SAQ-QOL scale at both baseline and 6-months post-PCI. As can be seen in Table
ESSI correlations with the SF-36 scales and the SAQ-QOL
Correlations at Baseline
SF-36 Social Functioning
SF-36 MHI
SF-36 PCS
SF-36 MCS
SAQ-AF
SAQ-QOL
ESSI Total
0.20
(p = .001)
0.36
(p < .001)
0.13
(p = .040)
0.31
(p < .001)
0.14
(p = .029)
0.22
(p = .001)
Correlations 6-Months Post-Revascularization
SF-36 Social Functioning
SF-36 MHI
SF-36 PCS
SF-36 MCS
SAQ-AF
SAQ-QOL
ESSI Total
0.33
(p < .001)
0.29
(p < .001)
0.20
(p = .004)
0.29
(p < .001)
0.18
(p = .008)
0.22
(p = .002)
Discussion
The present study confirms the concurrent and predictive validity and utility of the ESSI as an index of social support for use with PCI patients. The internal and test-retest reliability exceeds the recommended level of 0.70 for group assessments
The results also provide conceptual insight into the nature of social support. The majority of questions on the ESSI consider general feelings about being loved and valued rather than instrumental types of support. This supports the theory that social support is not a tally of actual supportive "services" rendered, but rather a patient's belief that others care about them and are available if needed
This study has several design limitations that should be noted. First, baseline social support was measured using a self-report questionnaire at the time of PCI and patient responses were not substantiated with family members, as would have ideally been the case. Secondly, the size and diversity of the patient sample was limited. With 271 patients and only 6% minorities, drawn from a single region of the United States, the population number and make-up limits the ability to generalize these results to the general population.
Despite these limitations, the results confirm the reliability and validity of the ESSI for gathering social support data among PCI patients. This study supports it's use in outcomes research that may help define the role of social support in affecting health outcomes. With psychometrically validated instruments in hand, future researchers should further elucidate the effects of social support on health and recovery in cardiac patients.
ENRICHD Social Support Instrument
Item 1
Is there someone avaliable to whom you can count on to listen to you when you need to talk?
None of
the time
□
A little of
the time
□
Some of
the time
□
Most of
the time
□
All of
the time
□
Item 2
Is there someone avaliable to you to give you good advice about a problem?
Item 3
Is there someone avaliable to you who shows you love and affection?
Item 4
Is there someone avaliable to help with daily chores?
Item 5
Can you count on anyone to provide you with emotional support (talking over problems or helping you make a difficult decision)?
Item 6
Do you have as much contact as you would like with someone you feel close to, someone in whom you can trust and confide in?
Item 7
Are you currently married or living with a partner?
Yes
□
No
□
Authors' contributions
JV conceived the study and drafted the manuscript. MC participated in coordination of the study and statistical analyses. CP participated in design and coordination of this project. JO & KH contributed to the conception of the study. JH performed the statistical analysis. JS oversaw the execution of this project and edited the manuscript. All authors have read and approved the final manuscript.
Acknowledgements
This project was supported, in part, by an unrestricted grant from Searle Pharmaceuticals and, in part, by R-01 HS11282-01 from the Agency for Healthcare Research and Quality.