One hundred and twelve studies (number of participants not stated) were included in the review: 93 RCTs and 19 non-randomised controlled trials.
Thirty-six studies (32%) scored 3 points on the Jadad scale for quality; none scored more than 3 points. Methodological limitations of the studies included a lack of double-blinding, although the authors acknowledged that this was often difficult in organisational interventions.
Overall results across all chronic conditions.
Fifty-two studies reporting continuous clinical outcomes for diabetes and depression found a significant improvement in the intervention group in comparison with the control group (effect size -0.23, 95% CI: -0.31, -0.15). Similarly, 46 studies reporting dichotomous clinical outcomes for all conditions found a significant effect in favour of the intervention group (RR 0.84, 95% CI: 0.78, 0.90). Quality of life (24 studies, all conditions) was found to be significantly improved in favour of the intervention group (effect size 0.11, 95% CI: 0.02, 0.21), as were process outcomes (32 studies; all conditions; RR 1.19, 95% CI: 1.10, 1.28).
Results according to chronic condition.
Continuous clinical outcomes in studies of depression (27 studies; effect size -0.25, 95% CI: -0.37, -0.13) and diabetes (25 studies; effect size -0.19, 95% CI: -0.29, -0.10) were found to be significantly in favour of the intervention. Dichotomous clinical outcomes in studies of asthma (9 studies; RR 0.82, 95% CI: 0.69, 0.98), CHF (19 studies; RR 0.81, 95% CI: 0.71, 0.92) and depression (14 studies; RR 0.83, 95% CI: 0.74, 0.93) were also found to be significantly in favour of the intervention. Only depression (3 studies; RR 0.18, 95% CI: 0.08, 0.28) and CHF (6 studies; RR 0.28, 95% CI: 0.06, 0.51) studies showed significantly improved quality of life outcomes in favour of the intervention; however, only 3 depression studies were included in the analysis, which may affect the reliability of the result. Process of care outcomes were significantly improved in favour of the intervention group in studies of depression (15 studies; RR 1.28, 95% CI: 1.11, 1.48) and diabetes (9 studies; RR 1.10, 95% CI: 1.01, 1.19).
Results according to CCM element.
Significant effects in favour of delivery system design were found for continuous clinical outcomes (33 studies; effect size -0.21, 95% CI: -0.40, -0.02), dichotomous clinical outcomes (30 studies; RR 0.77, 95% CI: 0.62, 0.96) and process of care (21 studies: RR 1.16; 95% CI: 1.01, 1.34). Significant effects in favour of self-management support interventions were found for continuous clinical outcomes (35 studies; effect size -0.22, 95% CI: -0.38, -0.05) and dichotomous clinical outcomes (36 studies; RR 0.81, 95% CI: 0.66, 0.99). Significant effects for decision support were only found for process of care (18 studies; RR 1.29, 95% CI: 1.08, 1.54). Clinical information systems, community resources and health care organisation were not shown to have significant effects when compared with control. The effects of quality of life, process of care and dichotomous clinical outcomes were not estimable for community resource interventions, owing to a lack of data.
Sensitivity analyses, meta-regression and publication bias.
None of the variables tested reached significance in the meta-regression analyses, and the pooled effects sizes from the sensitivity analyses (study quality) were similar to the overall effect sizes. Publication bias was noted for all CHF studies and asthma studies reporting dichotomous clinical outcomes.