Routine low-cost pathology tests: measuring the value in use of bacteriology tests in hospital and primary care

The introduction of a managed market in health care in the NHS will encourage managers and clinicians to examine clinical services, such as pathology, more closely. However, simple cost-minimization may not be sufficient; the recent Audit Commission report on pathology emphasises a need to measure and monitor cost-effectiveness of clinical services such as pathology. This paper presents the findings of a study to measure the cost-effectiveness of one routine pathology test; the culture and antibiotic susceptibility test performed by all microbiology laboratories. Over 2,900 requests were examined and test results tracked in hospitals and general practices served by three laboratories. The findings show that, although average test costs are low for the three main user groups (4.3-5.9 pounds), the cost of producing an effect on patient management (change to therapy) is high at 54-67 pounds. In addition to therapy changes, the one major effect recorded was that of clinician reassurance. If all measured effects are weighted by their reported clinical utility, cost-utility ratios of 27.0 pounds +/- 1.0 pounds, 45.5 pounds +/- 4.5 pounds and 44.5 pounds +/- 3.5 pounds per patient management effect are calculated for general practitioner, outpatient and inpatient use respectively. A theoretical model is presented which will allow the comparative cost-effectiveness of a range of routine diagnostic tests to be measured through the use of a test-utility index, similar to the health index which is currently used to measure the outcome of medical interventions (QALYs).