COST-EFFECTIVENESS OF NONINVASIVE DIAGNOSTIC AIDS IN SUSPECTED PULMONARY-EMBOLISM

Background: Noninvasive instruments such as plasma D-dimer measurement (DD) and lower-limb compression ultrasonogaphy (US) are being increas ingly advocated to reduce the number of necessary angiograms in patien ts having suspected pulmonary embolism (PE) and a nondiagnostic lung s can. We therefore designed a decision analysis model (1) to evaluate t he cost-effectiveness of combining these noninvasive diagnostic aids w ith lung scan and angiography in the diagnosis of PE and (2) to determ ine the optimal sequence and combination of tests taking into account the clinical probability of PE. Methods: We performed a cost-effective ness analysis based on literature data, including data from a manageme nt study in our institution. Six diagnostic strategies were compared w ith the reference, ie, lung scan followed when nondiagnostic (low or i ntermediate probability) by angiography. In all strategies, PE was rul ed out by a normal or near-normal scan, a negative DD (plasma level be low 500 mu g/L), or a negative angiogram. Pulmonary embolism was diagn osed and anticoagulant treatment was undertaken in the presence of a h igh-probability lung scan, deep vein thrombosis showed by US, or a pos itive angiogram. In case of a nondiagnostic scan (low or intermediate probability), patients could be either treated or not treated, or unde rgo other tests, according to the selected strategy. Results: Under ba seline conditions (prevalence of PE, 35%), strategies combining DD and US with lung scan, angiography being done only in case of an inconclu sive noninvasive workup (DD level >500 mu g/L, normal US, and nondiagn ostic lung scan), were most cost-effective. This approach yielded a 9% incremental cost reduction and a 37% to 47% decrease in the number of necessary angiograms compared with the reference strategy (scan +/- a ngiography). For patients with a low clinical probability of PE (less than or equal to 20%), withholding treatment from those with a low-pro bability lung scan without performing an angiogram proved safe and hig hly cost-effective (30% cost reduction), provided US showed no deep ve in thrombosis. Conclusion: The DD test and US are cost-effective in th e diagnostic workup of PE, whether performed after or before lung scan , thus allowing centers devoid of lung scanning and/or angiography fac ilities to screen patients with suspected PE and avoid costly referral s. In patients with a low clinical probability, a low-probability lung scan, and a normal US, treatment may be withheld without resorting to angiography.