Aims Repeat serum C-reactive protein (CRP) measurements on the same day or on consecutive days are of limited clinical value. Minimum retesting intervals are recommended for managing unnecessary repeat testing. As not previously reported, we studied the effect of minimum retesting interval test rejection on laboratory workload and expenditure and on clinician-requesting behaviour.

Methods In a prospective study, we evaluated the effect of an automated 48 h CRP minimum retesting interval rule on inpatient and outpatient CRP workload and costs. Control data on inpatient and outpatient serum urea and electrolytes (UE) workload were collected during the study.

Results Over 1 year, there was a 7.0% and 12.3% decrease in CRP requests and CRP tests analysed, respectively, following the introduction of the minimum retesting interval rule when compared to the 1 year baseline period. This equated to an estimated annual reduction in revenue costs of £10 500, but cash savings in consumable costs of £3000. There was no significant change in UE requests.

Conclusions We report, for the first time, that automated minimum retesting interval rejection rules as a stand-alone strategy are a cheap and sustainable method for reducing unnecessary repeat CRP tests, resulting in small laboratory cash savings, more efficient use of laboratory resources and standardisation of patient care pathways. The minimum retesting interval rejection rule also altered clinician test-requesting behaviour towards more appropriate requesting.