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BMJ Qual Saf. 2012 Aug;21(8):634-40. doi: 10.1136/bmjqs-2011-000737. Epub 2012 May 23.

Should measures of patient experience in primary care be adjusted for case mix? Evidence from the English General Practice Patient Survey.

Author information

1
Cambridge Centre for Health Services Research, University of Cambridge, Cambridge, UK.

Abstract

OBJECTIVES:

Uncertainties exist about when and how best to adjust performance measures for case mix. Our aims are to quantify the impact of case-mix adjustment on practice-level scores in a national survey of patient experience, to identify why and when it may be useful to adjust for case mix, and to discuss unresolved policy issues regarding the use of case-mix adjustment in performance measurement in health care.

DESIGN/SETTING:

Secondary analysis of the 2009 English General Practice Patient Survey. Responses from 2 163 456 patients registered with 8267 primary care practices. Linear mixed effects models were used with practice included as a random effect and five case-mix variables (gender, age, race/ethnicity, deprivation, and self-reported health) as fixed effects.

MAIN OUTCOME MEASURES:

Primary outcome was the impact of case-mix adjustment on practice-level means (adjusted minus unadjusted) and changes in practice percentile ranks for questions measuring patient experience in three domains of primary care: access; interpersonal care; anticipatory care planning, and overall satisfaction with primary care services.

RESULTS:

Depending on the survey measure selected, case-mix adjustment changed the rank of between 0.4% and 29.8% of practices by more than 10 percentile points. Adjusting for case-mix resulted in large increases in score for a small number of practices and small decreases in score for a larger number of practices. Practices with younger patients, more ethnic minority patients and patients living in more socio-economically deprived areas were more likely to gain from case-mix adjustment. Age and race/ethnicity were the most influential adjustors.

CONCLUSIONS:

While its effect is modest for most practices, case-mix adjustment corrects significant underestimation of scores for a small proportion of practices serving vulnerable patients and may reduce the risk that providers would 'cream-skim' by not enrolling patients from vulnerable socio-demographic groups.

PMID:
22626735
PMCID:
PMC3402750
DOI:
10.1136/bmjqs-2011-000737
[Indexed for MEDLINE]
Free PMC Article
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