Patterns of medical practice variation: variability in referral for back pain by New Zealand general practitioners

To describe patterns of variation in referral among general practitioners, and to establish whether variability among practitioners within a geographic area is associated with high levels of utilisation in an area.

Multilevel analysis of routinely collected primary care data. The four outcome measures were referral to physiotherapy, specialist assessment, radiology, and approval of earnings-related compensation.

The pattern of observed variability is not consistent for different referral activities: groups of general practitioners within one area may practice consistently in referral for one outcome, but be highly variable for another, while practitioners in other areas can show the reverse pattern. The degree of variability among GPs within geographic areas was not significantly correlated at the 95% level with the absolute level of referral to any of the referral options.

The mechanisms which drive variability operate at the level of the specific clinical management option, rather than at the level of the overall approach to management of the disease. Caution should be exercised about claims that reductions in variability will produce reductions in utilisation.