The general practitioner and laboratory utilization: why does it vary?

In a study of the practice patterns of 128 general practitioners in Northern Norway information concerning 6848 surgery consultations was registered. The ordering of haemoglobin and sedimentation tests was noted as well as urinalyses, forwarding of biological specimens (blood, urine, smears, etc) to other laboratories, and referrals for X-ray examinations. The extent to which doctors ordered these tests varied widely (haemoglobin 0-72% of encounters, urinalyses 0-70%, forwarding of tests 0-56%). Fee-for-service doctors ordered urine microscopy more frequently than did their salaried colleagues, but the ordering of haemoglobin or sedimentation test, and the forwarding of biological samples was about the same. Female and older doctors as well as doctors trained in Norway tended to request tests more often. Laboratory utilization was higher in municipalities with a high turnover of doctors, but the doctors' years of postgraduate experience per se did not affect the extent of test ordering. Tests were requested more often for female patients and with increasing age of the patient. However, only 10% of the variation in laboratory utilization was explained by the variables used in the analyses. This may imply that the medical condition at hand is the strongest determinant of test ordering behaviour.