Reduced efficacy of clinical probability score and D-dimer assay in elderly subjects suspected of having deep vein thrombosis.

The combined strategy of a pretest clinical probability (PCP) score and D-dimer has shown to be of value in the diagnosis of deep vein thrombosis (DVT). As D-dimer concentrations increase with age, the effect of age on the usefulness of this strategy was retrospectively investigated in outpatients suspected of having DVT. In all patients, participants of a prospective management trial, a PCP score and D-dimer (Tina-quant) were performed. In a total of 812 patients, 317 (39%) had thrombosis. Patients were divided into quartiles according to their age. Sensitivity and negative predictive value of a low/moderate PCP score and a normal D-dimer were 98-100% and did not differ between the different age quartiles. Specificity in the highest quartile was 17.4% compared with 49.2% in the youngest (P < 0.000001). The proportion of patients with a low/moderate PCP score and a normal D-dimer decreased with age: 12% in the highest quartile (>73.8 years) versus 25% in younger patients (P = 0.00005). We therefore conclude that the combined strategy of a low/moderate PCP score with a normal D-dimer test is safe for excluding DVT in all age groups, but is less useful in the elderly.