Meta-analyses: Heterogeneity and Subgroup Analysis

Philip Sedgwick
Reader in medical statistics and medical education
Centre for Medical and Healthcare Education, St George’s, University of London, London, UK

Researchers undertook a meta-analysis to evaluate the effectiveness of comprehensive geriatric assessment in hospital for older adults admitted as an emergency. They included randomised controlled trials that compared comprehensive geriatric assessment with usual care. Comprehensive geriatric assessment is a multidimensional interdisciplinary diagnostic process used to determine the medical, psychological, and functional capabilities of a frail elderly person so as to develop a coordinated and integrated plan for treatment and long term follow-up. Usual care usually involved admission to a general medical ward setting under the care of a non-specialist. Twenty two trials were identified, evaluating 10315 participants in six countries.(1) 

The primary outcome was “living at home” at the end of the scheduled follow-up period. This outcome was reported by 18 trials evaluating 7062 participants. The median follow-up was 12 months (range six weeks to 12 months). The test of heterogeneity for these trials gave χ2=28.49, df=17, P=0.04, I2=40%. The total overall estimate indicated that the odds of a patient living at home at the end of scheduled follow-up were significantly higher in those patients who had undergone comprehensive geriatric assessment than in those who received usual care (odds ratio=1.16 (95% confidence interval 1.05 to 1.28; P=0.003)).

Subgroup analysis was undertaken, based on the type of model of comprehensive geriatric assessment performed. Two broad types of model were identified: assessment in designated wards by a coordinated specialist team; and assessment by mobile teams wherever the patient was admitted. The test of heterogeneity for “ward” gave χ2=17.66, df=13, P=0.17, I2=26% while that for “team” gave χ2=1.86, df=3, P=0.60, I2=0%.

The subtotal estimate for “ward” indicated that comprehensive geriatric assessment was significantly more likely to result in patients being in their own homes at the end of scheduled follow-up than was usual care (odds ratio 1.22 (1.1 to 1.35; P<0.001)). However, when comprehensive geriatric assessment was undertaken by mobile teams its effects were inconclusive in comparison with usual care (odds ratio 0.75 (0.55 to 1.01; P=0.06)). The test for subgroup differences gave χ2=9.06, df=1, P=0.003, I2=89%.

Competing interests: None declared.
1. Ellis G, Whitehead MA, Robinson D, O’Neill D, Langhorne P. Comprehensive geriatric assessment for older adults admitted to hospital: meta-analysis of randomised controlled trials. BMJ 2011;343:d6553.

Cite this as: BMJ 2013;346:f4040