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PAPERS: Tiina M Huusko, Pertti Karppi, Veikko Avikainen, Hannu Kautiainen, and Raimo Sulkava Randomised, clinically controlled trial of intensive geriatric rehabilitation in patients with hip fracture: subgroup analysis of patients with dementia BMJ 2000; 321: 1107-1111 [Abstract] [Full text]

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Assesment of grouping variable should also be blinded

Petri E Voutilainen   (17 February 2001)

Assesment of grouping variable should also be blinded 17 February 2001
Petri E Voutilainen, Trialist, MD Department of Surgery, Helsinki University Central Hospital, Helsinki, Finland Send response to journal: Re: Assesment of grouping variable should also be blinded	Dear Editor, I read with interest the article by Dr Huusko1 and colleagues on the effect of intensive geriatric rehabilitation on demented patients with hip fracture. The study was probably the first randomized study with predetermined subgroup analysis according to level of dementia on this increasing patient group. The level of dementia was classified by mini mental state examination score.2 The median length of hospital stay of hip fracture patients with moderate dementia was 47 days in the intervention group and 147 days in the control group (p = 0.04). The corresponding figures for patients with mild dementia were 29 days in the intervention group and 46.5 days in the control group (p = 0.002). It was concluded that, hip fracture patients with mild or moderate dementia can often return to the community if they are provided with active geriatric rehabilitation. Pioneers work is never easy, either in this case. Even though the study seemed to bee well conducted, the patients in the intervention group were stated to have a highly significantly deeper level of dementia as compared with the control group (p < 0.001). This was considered as coincidental even though, such a difference in outcome would be considered as a definitive proof of treatment effect in any medical trial. The level of dementia was used as grouping variable when testing the effect of intervention on the outcome, and thus probably had a fundamental effect on the obtained results. Problem is that the level of dementia was stated about one week after admission to the geriatric ward of the central hospital or the local hospital, 10 days after surgery and randomisation! Obviously the person making the mini mental scoring knew the treatment group, and probably the person was different in the control, and in the intervention group. This may have caused biased classification of dementia, and may explain the observed difference in mini mental state examination, between the study groups.3 Thereafter, recovery of patients in the intervention group without true dementia may have been compared with patients in the control group with mild dementia and so on, which might explain significant part of the observed results in the study. Obviously conduction of this kind of randomized study is very demanding, but it would be highly recommended to try to blind assessment of the main grouping factor. Reference List 1. Huusko TM, Karppi P, Avikainen V, Kautiainen H, Sulkava R. Randomised, clinically controlled trial of intensive geriatric rehabilitation in patients with hip fracture: subgroup analysis of patients with dementia. BMJ 2000;321:1107-1111. 2. Folstein MF, Folstein SE, McHugh PR. "Mini-mental state". A practical method for grading the cognitive state of patients for the clinician. Journal of Psychiatric Research 1975;12:189-198. 3. Schulz KF. Subverting randomization in controlled trials. JAMA 1995;274:1456-1458.