An evaluation of ambulatory visit groups in rheumatology out-patients.

The development of case mix measures for National Health Service (NHS) care has become of great importance recently. Much effort has been put into devising measures for in-patient care, but measures for ambulatory (outpatient, day care and primary care) visits are less developed. Ambulatory Visit Groups (AVGs) is an American system devised to aggregate ambulatory visits into iso-resource groups. However, some assumptions made in the construction of the AVG system may not hold for the UK health service, including the use of consultation time as a proxy for the total resource use associated with the out-patient attendance. To test AVGs in the UK context, a three-month prospective study of rheumatology out-patient attendances at two hospitals in Newcastle upon Tyne assembled a database of 3393 'visits', together with resource use data. The AVGs derived from these were analysed to evaluate the homogeneity of the groups with respect to consultation resource use, and the degree to which consultation time can be considered a proxy for resource use in this setting. Consultation time distributions were markedly skewed, and required log transformation before analysis. Variation in log consultation time was found to depend as much on the clinician as on the AVG, and the two were observed to interact. Resource use distributions were also skewed, and were similarly transformed for analysis. Non-parametric analysis of variance showed resource use to be significantly associated with AVG, but the amount of variation associated with the AVG appeared to be small and inconsistent.(ABSTRACT TRUNCATED AT 250 WORDS)