In comparing performance of the SCQ and CCI, we found the CCI did not predict the quality of life EQD5 scores after ACS. The CCI was not significantly associated with the EQ5D scores at three months and at eight months after hospitalization for ACS. The SCQ, however, more significantly predicted the EQD5 scores at three-months, and at eight months follow-up. However, CCI is almost as predictive as the SCQ for ASI functional capacity scores at three and eight months, and performing more significantly in predicting quality of life at eight-month follow-up.
Our findings are particularly important because our follow-up period allowed longer post-discharge assessment of functional capacity and quality of life at intervals longer than 30-day mortality, as is most often the case when administrative data are used [9, 40, 41]. As we reported previously, patients reported more of certain comorbidities using the self-report instrument compared with the medical record .
Our results indicate that having additional co-morbidities, as self-reported by patients are relatively strong predictors of quality of life (EQ5D scores); and functional capacity (ASI scores). On average, our analysis revealed that they decline by -0.02 (p < 0.001); and -2.00 (p< 0.001) for each unit increase in the self reports CCI (Katz scores) for the EQ5D and ASI respectively. Similarly, Motl et al  found statistically significant inverse associations between the number of self-reported cardiovascular comorbidities and objectively measured and self-reported physical activity. Their study revealed that physical activity levels in persons with muscular sclerosis were associated with the number of self-reported cardiovascular comorbidities, independent of disability status, and other possible cofounding influences. In another smaller study, Bayliss et al  found that for certain quality of life assessments, self-reported comorbidity data may provide a more accurate estimate of comorbidity than existing medical record reporting sources. Susser et al  compared the predictive validity of self report and administrative CCI using subsequent health services utilization rates and functional decline as outcomes. In contrast to our finding, they found that agreement between self-report and administrative comorbidity data was only poor to fair but both have comparative levels of predictive validity.
Our study also found that higher depressive symptom levels (CESD scores; -0.011, p < 0.001; -0.411, p < 0.001) were significantly associated with both patients’ quality of life and functional capacity. More depressed patients in our sample consistently had lower levels of quality of life and functional capacity after a hospitalization for ACS.
In our multivariate models, certain factors such as age, gender, family income and CESD were significantly associated with the Charlson CCI and self report SCQ in predicting functional capacity. The self-report comorbidity measure more significantly predicted QOL during the eight-month study window.
Male ACS patients generally demonstrated higher QOL and functional capacity levels after discharge. In addition, patients with higher family incomes (> $40,000) did seem to experience both a higher quality of life and level of functional capacity. For future studies, these patterns suggest that research interventions and analyses will need to be effectively targeted to capture differential influences of these factors on many health outcomes.
Katz and colleagues have continued to develop and validate the SCQ in populations of general surgical patients in hospital settings . In addition, a German version of the SCQ, the SCQ-D has recently been developed . The comorbidity measured by the SCQ-D proved to be a valid predictor of the hospitalization and the treatment outcome .
There are several limitations of this study. First, the majority of these post discharge data came from a sample of hospitalized patients with ACS from specific community hospitals in the Midwest. Second, the use of hospital medical records may have limited our ability to capture all the patients’ documented conditions as this is affected by the quality of documentation. Wording differences between self-report source (i.e. before your hospitalization) and medical record source (designed to capture both current and past conditions) items may account for some of our observed differences.