Laboratory expenditure in Pegasus Medical Group: a comparison of high and low users of laboratory tests with academics

Aims. To determine, through the use of clinical vignettes, whether low and high cost users of laboratory tests in Pegasus Medical Group (Pegasus) diff ered in their choice of laboratory tests from academics as a means of furth er investigating issues relating to quality and cost in laboratory testing. Methods. Seven clinical vignettes were drawn up and sent :to 30 selected me mbers in Pegasus whose actual laboratory expenditure per consultation range d from a mean of $2.3 in a low cost group (15 members) to $12.2 in a high c ost group (15 members). The vignettes were also sent to 15 general practiti oner academics. Respondents were requested to complete a laboratory form as to which tests they would use for each individual scenario. The answers we re analysed for overall cost as well as numbers of laboratory tests request ed. Results. There were 14 academic responses and 13 each from the bottom and t op laboratory users. Overall results for the seven vignette cases showed th at low cost laboratory users would spend a total of $176.3, the academics $ 188.8, and the high cost users $219.5 on the cases. The mean per case costs were $25.2, $27.0 and $31.4 respectively. There was a clear tendency for h igh volume users of tests in each vignette to be high in others suggesting that doctor rather than patient factors were the main explanation of the va riation. Conclusions. Clinical vignettes do not appear to be a useful strategy in cl arifying issues related to quality and cost in laboratory utilisation. Test ordering behaviour appears, from the international literature and this stu dy, to be determined more by personal doctor factors than by objective evid ence and clinical need. Further work is needed to clarify the relationship between quality and the wide variation observed in utilisation and expendit ure.