Susan M Smith, Gráinne Cousins, Barbara Clyne, Shane Allwright, Tom O'Dowd

Shared care has been used in the management of many chronic conditions with the assumption that it delivers better care than primary or specialty care alone; however, little is known about the effectiveness of shared care. To determine the effectiveness of shared care health service interventions designed to improve the management of chronic disease across the primary/specialty care interface. This is an update of a previously published review.Secondary questions include the following:1. Which shared care interventions or portions of shared care interventions are most effective?2. What do the most effective systems have in common? We searched MEDLINE, Embase and the Cochrane Library to 12 October 2015. One review author performed the initial abstract screen; then two review authors independently screened and selected studies for inclusion. We considered randomised controlled trials (RCTs), non-randomised controlled trials (NRCTs), controlled before-after studies (CBAs) and interrupted time series analyses (ITS) evaluating the effectiveness of shared care interventions for people with chronic conditions in primary care and community settings. The intervention was compared with usual care in that setting. Two review authors independently extracted data from the included studies, evaluated study quality and judged the certainty of the evidence using the GRADE approach. We conducted a meta-analysis of results when possible and carried out a narrative synthesis of the remainder of the results. We presented the results in a 'Summary of findings' table, using a tabular format to show effect sizes for all outcome types. We identified 42 studies of shared care interventions for chronic disease management (N = 18,859), 39 of which were RCTs, two CBAs and one an NRCT. Of these 42 studies, 41 examined complex multi-faceted interventions and lasted from six to 24 months. Overall, our confidence in results regarding the effectiveness of interventions ranged from moderate to high certainty. Results showed probably few or no differences in clinical outcomes overall with a tendency towards improved blood pressure management in the small number of studies on shared care for hypertension, chronic kidney disease and stroke (mean difference (MD) 3.47, 95% confidence interval (CI) 1.68 to 5.25)(based on moderate-certainty evidence). Mental health outcomes improved, particularly in response to depression treatment (risk ratio (RR) 1.40, 95% confidence interval (CI) 1.22 to 1.62; six studies, N = 1708) and recovery from depression (RR 2.59, 95% CI 1.57 to 4.26; 10 studies, N = 4482) in studies examining the 'stepped care' design of shared care interventions (based on high-certainty evidence). Investigators noted modest effects on mean depression scores (standardised mean difference (SMD) -0.29, 95% CI -0.37 to -0.20; six studies, N = 3250). Differences in patient-reported outcome measures (PROMs), processes of care and participation and default rates in shared care services were probably limited (based on moderate-certainty evidence). Studies probably showed little or no difference in hospital admissions, service utilisation and patient health behaviours (with evidence of moderate certainty). This review suggests that shared care improves depression outcomes and probably has mixed or limited effects on other outcomes. Methodological shortcomings, particularly inadequate length of follow-up, may account in part for these limited effects. Review findings support the growing evidence base for shared care in the management of depression, particularly stepped care models of shared care. Shared care interventions for other conditions should be developed within research settings, with account taken of the complexity of such interventions and awareness of the need to carry out longer studies to test effectiveness and sustainability over time.