CGA conducted on dedicated geriatric wards has proven to be beneficial for frail older patients [1, 4, 6–9], but the effectiveness of IGCTs remains unclear. In the current systematic review and meta-analysis, we were unable to document any favorable effect of IGCT interventions on functional status in older hospitalized patients, our primary outcome. Although most studies used the Barthel Index to assess basic activities for daily living, there was a high percentage of heterogeneity at all time points. Furthermore, there was a strong ceiling effect of most of the functional measures used, which is unfortunately a frequent limitation of these types of studies and may have limited the ability to detect improvements over time. Although a significant reduction in mortality rate was found at 6 and 8 months follow-up in intervention patients, this effect was not confirmed at any of the other follow-up points, including the 1-year follow-up, which combined the results of nine individual studies.
No effect of the intervention was found on the readmission rate at 1, 3, 6 and 12 months of follow-up, although it should be mentioned that only one study clearly reported unplanned readmission rate . Because planned readmissions cannot, and probably should not, be prevented, 'avoidable readmission rate' would have been a better outcome measure. However, preventability of readmissions remains an understudied topic . A recent systematic review of 34 studies found wide variation (ranging from 5% to 79%) in the percentage of readmissions considered preventable . There was, however, only one validated prediction model that explicitly examined potentially preventable readmissions as an outcome .
IGCT intervention is sometimes perceived by healthcare workers as a strategy that may prolong the patient's length of stay. However, we could not find any effect of IGCT on the length of the hospital stay.
Our analyses come with methodological limitations, the main being the heterogeneous way in which IGCTs are organized and put into practice. Because of the complexity of the interventions, explicit instructions are required to improve the consistency and reproducibility of the intervention. Although all studies reported the use of a formal multidisciplinary CGA in the intervention, the exact composition of the team, the frequency of interdisciplinary meetings, and the frequency of patient visits varied greatly or was not described in sufficient detail in the individual studies. Characteristics of the country (for example, healthcare and insurance system) and the hospital (for example, admission and discharge policy), rarely discussed in the studies, may also have affected the impact of the intervention, especially on outcomes such as length of stay and readmission rate. Additionally, in the study by Shyu et al., the geriatric consultation was accompanied by a rehabilitation program that was partly delivered by a geriatric nurse [28, 29]. This more elaborate intervention may explain the positive effect on functional status in this particular study, but there remains a lack of effect of the intervention on functional status after meta-analysis.
Because IGCTs constitute an advisory model, another important factor that could explain the limited impact of the intervention may be the lack of adherence to the recommendations made by the IGCT. The overall adherence rate to the IGCT recommendations was only reported in three of the included studies [19, 32, 36]. The nonadherence rate ranged from 23% to 33%, providing strong evidence that the intervention does not meet its full potential. Having control over the care process is one of the key differences between the two CGA models and could be one of the main reasons why the CGA ward type is effective and the team type (IGCT) is not.
Improved targeting to patients who will benefit most from an IGCT intervention has also been suggested to make this type of intervention more effective . Unfortunately, the extent to which patient characteristics contribute to the outcome of IGCT intervention could not be assessed because of the small number of studies included, precluding subgroup meta-analyses. Commonly used screening tools, like the Triage Risk Screening Tool  or the Identification for Seniors at Risk , might be helpful in identifying patients at the greatest risk for functional decline, but these instruments are limited by low specificity and low positive predictive value [40, 41]. This results in a high number of false-positives and the investment of a significant amount of time and manpower in older persons unlikely to benefit from IGCT in-depth comprehensive geriatric assessment or interventions.
Despite the methodological quality of the included studies ranging from moderate to good, they all performed poorly with regard to blinding of patients and/or assessment team. It is difficult to meet all criteria with high methodological quality in this research area - that is, complex multidisciplinary interventions with face-to-face contact. This is a further limitation that hampers progress .
Finally, we acknowledge that only a limited number of major outcomes was studied in our analysis; other outcomes must also be considered in the discussion of an IGCT. For example, in four studies, an IGCT intervention had a significant impact on cognitive outcome, such as incidence of delirium or improvements in the Mini-Mental State Exam or the Geriatric Depression Scale [21, 28, 32, 42]. Among other outcomes, cognitive status is a clinically important indicator that should be considered in further studies.