A cost-effectiveness analysis of diagnostic algorithms of deep vein thrombosis at the emergency department

Suspected cases of deep vein thrombosis are common at emergency departments and they often require extensive and costly diagnostic testing. The objective of this study was to evaluate whether a diagnostic algorithm based upon pre-test probability and D-dimer in diagnosing deep vein thrombosis may be cost-effective from a societal perspective in a Swedish setting.

The cost-effectiveness of two alternative diagnostic algorithms were calculated using decision analysis. An algorithm which out ruled deep vein thrombosis among low probability patients with negative D-dimer was compared to a traditional algorithm including compression ultrasonography and/or contrast venography for all patients. For sensitivity analysis, a third reversed algorithm, where D-dimer was followed by pre-test probability, was analyzed. Estimates of probabilities were obtained from a prospective management study, including 357 outpatients with clinical suspicion of deep vein thrombosis. Direct costs were estimated using prices from Scania, Sweden. Indirect costs were estimated using time spent at the local emergency department and gross average wages in Sweden.

The total cost of the pre-test probability and D-dimer algorithm was estimated to euro406 per patient and the traditional algorithm was estimated to euro581 per patient. Reversing the order of the score and test resulted in an estimate of euro421 per patient.

At no significant difference in diagnostic efficacy the algorithm based upon pre-test probability and D-dimer was cost-effective, while the reversed algorithm and diagnostic imaging for all patients were not.