The diagnosis of deep venous thrombosis using laser Doppler skin perfusion measurements

Compression ultrasonography (CUS) falls short in the diagnosis of deep venous thrombosis in asymptomatic patients and thrombi limited to the calf veins. Alternatively, laser Doppler fluxmetry (LDF) may be useful for this purpose, as it can measure the peripheral vasoconstriction response upon an increase in venous pressure, which is hypothetically preactivated upon venous damming by a thrombus. We investigated the merits of LDF in the diagnosis of DVT. In 81 outpatients, referred with clinically suspected unilateral DVT, skin perfusion in the symptomatic and contralateral legs was measured in the big toe by measuring resting flux (RF) before and during an increase in venous pressure by inflating an ankle cuff to 50 mm Hg. The percentage of LDF reduction (LDFr) was used as a parameter to detect DVT and compared with an independent gold standard (a combination of CUS, D-dimer testing, and 3-month clinical follow-up). The prevalence of DVT was 31%. LDFr in symptomatic legs with DVT [24%; interquartile range (IQR) 8-44%] was significantly (P < 0.001) lower than in symptomatic legs without DVT (60%; IQR 44-70%). Assessment of the diagnostic accuracy of LDF yielded an area under the ROC curve of 0.79. The optimum cutoff value resulted in a sensitivity and a specificity of 80 and 72%, respectively. LDFr is reduced in legs with DVT, supporting the hypothesis of preactivation of the peripheral vasoconstriction response. The diagnostic value of LDF measurements is not likely to surpass that of CUS in symptomatic patients, but may be of additional use in situations where CUS is less sensitive.