EFFECT OF CORRECTING OUTCOME DATA FOR CASE-MIX - AN EXAMPLE FROM STROKE MEDICINE

Citation
Rj. Davenport et al., EFFECT OF CORRECTING OUTCOME DATA FOR CASE-MIX - AN EXAMPLE FROM STROKE MEDICINE, BMJ. British medical journal, 312(7045), 1996, pp. 1503-1505
Citations number
15
Categorie Soggetti
Medicine, General & Internal
ISSN journal
09598138
Volume
312
Issue
7045
Year of publication
1996
Pages
1503 - 1505
Database
ISI
SICI code
0959-8138(1996)312:7045<1503:EOCODF>2.0.ZU;2-9
Abstract
Objective-To show the influence of variations in case mix on clinical outcome indicators for patients admitted to hospital with acute stroke . Design-''Before and after'' cohort study, with prospective, consecut ive identification of patients and prospective follow up; multiple log istic regression analyses to correct for case mix variations. Setting- University teaching hospital. Subjects-216 patients with stroke identi fied before the introduction of an organised stroke service, and 252 p atients with stroke identified after its introduction. Main outcome me asures-Case fatality at 30 days and 12 months; for survivors at 12 mon ths, proportions of patients who were independent (according to the Ox ford handicap scale) and of those living at home. Results-Crude outcom e data suggested that patients in the cohort identified after the intr oduction of the stroke service were significantly more likely to be al ive, independent, and living at home than patients managed before the stroke service. After adjustment for age and sex these ''improvements' ' were less impressive but still significant. After adjustment for man y other possible prognostic indicators, however, the differences betwe en the two groups for all four outcomes were non-significant, suggesti ng that the ''improvements'' may have been entirely due to differences in case mix between the two cohorts, rather than the new stroke servi ce. Conclusions-Variations in case mix have a crucial influence on the interpretation of outcome data, and this is particularly important in non-randomised comparative studies. Such studies, comparing performan ce within and between different provider units, are likely to become i ncreasingly common in the new reformed NHS. To allow meaningful interp retation, these studies must try to correct for case mix.