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

Abstract

ObjectivesUncertainties 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/settingSecondary 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 measuresPrimary 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.ResultsDepending 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.ConclusionsWhile 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.

Measuring Patient Experience: Concepts and Methods

“…For example, in English primary care, patients report more negative experiences in practices with a higher proportion of younger patients, ethnic minorities, and patients living in more socio-economically deprived areas [31]. This could be because they receive worse care, or because the expectations of some population groups are different, or because they interpret the questions in survey instruments in different ways.…”

“…What case-mix adjustment does do is to allow comparisons between different sites to be made without the immediate complaint from care providers that the patient populations are not comparable. For example, practices gaining most from case-mix adjustment in English primary care were on average smaller and treated patients who tended to be younger, ethnic minorities, living in more socio-economically deprived areas, and in worse health compared with patients from other practices [31]. Adjusted data therefore have the potential to allow fairer comparison between health practices and/or providers.…”

“…In practice, adjusting for patient characteristics in either primary care or hospitals has a relatively small impact on unadjusted values, though the effects tend to be greatest for providers serving vulnerable populations [31,36]. In addition to ethnicity and deprivation, other variables to consider in the context of case-mix include age, sex, self-reported health status, and presence of longstanding psychological or emotional conditions [31,36].…”

“…Adjusted data therefore have the potential to allow fairer comparison between health practices and/or providers. The argument against case-mix adjustment is that it may be a way of institutionalising sub-standard care by masking poor care provided to some patient subgroups, and therefore some argue that both adjusted and unadjusted data on patient experience should be reported [31,36].…”

Data and performance: can education and health learn from each other?

“…practice performance data, 9 such as QOF and patient experience scores, are not adjusted for deprivation or any of the other factors, such as disability, which may have an impact on general practice performance.…”