The present meta-review is restricted to published systematic reviews of randomized controlled trials (RCTs) that compare patients who received conventional care with those who had one or more of the following broad clinical interventions [13
Hospital – based interventions
1. Discharge planning: an all-inclusive term for providing patients with information about their disease, or / and educating patients for following prescribed treatment plans, or / and ensuring communication between the members of the medical team, or / and assessing the patient's support networks, or / and post-discharge services, or / and arranging for follow-up.
2. Pharmacological consultations: a review of the patient's medications by a pharmacist with a view of improving the patient's knowledge of, and compliance with, the treatment regimen, identifying medication \ discrepancies, drug reactions or interactions.
3. Geriatric consultations, or comprehensive geriatric assessment programs: a review by geriatricians with advice on diagnostic evaluations, therapy, rehabilitation, social care and placement.
4. Case management: a systematic approach to care of patients with multiple chronic disorders.
5. Disease management: a systematic approach to care of patients with a specific chronic disease, such as stroke or congestive heart failure. Disease management programs may be implemented in specific in hospital units or through clinical guidelines / pathways.
6. In hospital management units: hospital wards, staffed by doctors, nurses and other health professionals for diagnostic assessment, therapy, rehabilitation and placement of patients in order to intensify post discharge care, identify effective community services and enhance primary care access.
Community – based interventions
1. Periodic home visits by professional care providers, single or multi-disciplinary. The service may be provided either by a "Disease manager" (for patients with a specific chronic disease), or by a "Case manager" (for patients with multiple diseases).
2. Self-management: Patient education for self-monitoring with a view of enabling patients to assume responsibility for managing one or more aspects of their disease by medication dosage adjustment or by recognizing a need for medical assistance.
3. Telephone follow-up aimed at exchanging information, providing health education and advice, managing symptoms, recognizing complications and giving reassurance.
4. Telemonitoring of physiological variables measured by patients at home.
5. Community - based rehabilitation programs
6. Day care
7. Hospital at home
The participants in the RCTs were inpatients or outpatients who were believed to be at risk of increased HRR. It should be noted that most systematic reviews of the effect of such intervention synthesize a heterogeneous collection of primary studies that may differ in duration of follow-up, frequency of contacts with care providers and their professional backgrounds.
We used all-cause HRR as the outcome of interest, and, unless otherwise stated, ignored reported rates of disease specific readmissions, or of readmissions that were believed by the authors to be preventable. We are aware that disease specific readmission rates are a better indicator of the efficacy of interventions than all-cause HRR. Still, the vast majority of published systematic reviews address all-cause HRR, which are readily available from hospital databases. On the other hand, the distinction between preventable and unavoidable readmissions requires a painstaking review of medical records, and even then, the reliability (i.e., agreement between evaluators) of the distinction is only moderate [19
Electronic searches and selection of systematic reviews
We searched the literature without language restriction, using the electronic data bases and key terms listed in Additional file 1
: Appendix 1 from inception until September 2012, as well as the reference lists of the retrieved articles. We did not seek further information from authors of individual systematic reviews and we did not review the gray literature. One of us (JB) screened the identified titles / abstracts and excluded studies that obviously did not meet the inclusion criteria, namely, systematic reviews of RCTs of the effect of clinical interventions on HRR that presented their findings either in terms of risk / odds ratios and 95% confidence intervals, or in other presentations formats. Both authors reviewed the full text of the remaining papers, and, after resolving differences in opinions by discussions, further excluded systematic reviews that did not meet the inclusion criteria or met / fulfilled one or more of the following exclusion criteria:
1. Duplicate systematic reviews or availability of an updated systematic review.
2. Studies of pediatric, obstetric, terminal and psychiatric patients.
3. Studies of the effect of disease specific diagnostic (e.g., angiography) or treatment (e.g., laparoscopic surgery) interventions on hospital readmissions.
4. Protocols of planned studies and models predicting readmissions, position statements and methodology papers.
5. Reviews that failed to identify any eligible studies in the literature search.
6. Interventions targeted at care providers rather than at patients.
7. Primary research studies, i.e., reports of single trials.
We used a predetermined format to stratify the selected systematic reviews by method of data synthesis (meta-analyses, or systematic reviews that presented their findings using other formats), setting of intervention (hospital only, or community with and without inhospital interventions), patient populations (unselected patients, or patients with specific disorders) and type of intervention (e.g., discharge planning, home care). Some systematic reviews synthesized RCTs at both settings of care, involving two or more patient populations, or two or more types of interventions, and, therefore, they are referred to more than once in the same or different tables.
Most selected systematic reviews were meta-analyses that presented their findings in terms of risk or odds ratios with 95% confidence intervals. The advantage of meta-analyses is that they take into account the power of the primary studies. However, the heterogeneity in the implementation of the same clinical interventions, in the professionals who implemented them, in the patient populations and in the duration of follow-up detracts from the credibility of the synthesis of various RCTs. Some reviews did not discern between RCTs and non-randomized controlled trials. In such cases, we retrieved the primary studies, selected the RCTs only, and re-synthesized their results using the Meta-Analyst software [21
The remaining systematic reviews synthesized their findings using formats other than risk ratios, mostly in terms of proportion of RCTs reporting significantly reduced HRR. Their advantage is that they present separately the results of the primary RCTs, and thereby avoid averaging the results of possibly heterogeneous studies. However, by implicitly assigning the same weight to the reviewed RCTs, such systematic reviews may overemphasize studies that failed to detect a significant reduction in HRR because of low power.
Quality assessment of the systematic reviews
One of us (JB) assessed the quality of the identified reviews according to the 11 AMSTAR methodological criteria [22
] on a 0–11 scale. We felt that these criteria were clear cut and that a single investigator was capable of applying them. Indeed, the AMSTAR scores in the present overview differed by 1 or less in 14 of the 15 meta-analyses that were included in the overview by Savard et al. [17
We interpreted the 4th AMSTAR criterion (use of status of publication as an inclusion criterion) as the presence of a reference to the grey literature or a statement that the authors of the reviewed RCTs were contacted for additional information. The 9th AMSTAR criterion (use of appropriate methods to combine the study findings) was interpreted as requiring either an assessment of heterogeneity (in case of meta-analyses), or a presentation of the findings, which permitted a calculation of the proportion of RCTs that found significant differences in HRR (in case of other systematic reviews). The 'results' section is restricted to the findings of the meta-analyses only, regardless of their quality; the summary and conclusions in the 'discussion' section are based on meta-analyses with an AMSTAR score of 7 or more.