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

To determine, through the use of clinical vignettes, whether low and high cost users of laboratory tests in Pegasus Medical Group (Pegasus) differed in their choice of laboratory tests from academics as a means of further investigating issues relating to quality and cost in laboratory testing.

Seven clinical vignettes were drawn up and sent to 30 selected members in Pegasus whose actual laboratory expenditure per consultation ranged from a mean of $2.3 in a low cost group (15 members) to $12.2 in a high cost group (15 members). The vignettes were also sent to 15 general practitioner academics. Respondents were requested to complete a laboratory form as to which tests they would use for each individual scenario. The answers were analysed for overall cost as well as numbers of laboratory tests requested.

There were 14 academic responses and 13 each from the bottom and top laboratory users. Overall results for the seven vignette cases showed that 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 high 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 variation.

Clinical vignettes do not appear to be a useful strategy in clarifying issues related to quality and cost in laboratory utilisation. Test ordering behaviour appears, from the international literature and this study, to be determined more by personal doctor factors than by objective evidence and clinical need. Further work is needed to clarify the relationship between quality and the wide variation observed in utilisation and expenditure.