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Independents' Day

Can we safely ignore borderline D-dimer?

QIs it safe to ignore a mildly raised

D-dimer?

AVenous thromboembolism (VTE) is common, with annual incidence of one in 1,000 and a fatality rate of

5 per cent. Elevated plasma D-dimers, cross-linked fibrin derivatives above 500ng/ml, are sensitive markers for thrombosis within the preceding week. But various physiological and pathological states increase D-dimers, including pregnancy, age over 70, post-operative, inflammation, infection, cancer and renal failure.

So this test is non-specific and cannot alone be used to confirm VTE, which requires compression ultrasound, ascending venography, VQ scan or pulmonary arteriography. Fortunately, studies confirm the value of the pre-test probability score, assigning one point each to the presence of active cancer, lower limb immobilisation, bedridden for more than three days, major surgery less than four weeks ago, vein tenderness, entire leg swelling, calf-swelling larger than 3cm, pitting oedema, collateral veins.

A score of one or two points indicates moderate probability, with three points indicating high probability of VTE. The incidence may be 20 per cent in patients with a high pre-test probability score and 'negative' D-dimers less than 500ng/ml, so D-dimers alone cannot exclude VTE.

Recent VTE can be excluded with low pre-test probability score and 'negative' D-dimers (incidence <1 per="" cent).="" it="" is="" safe="" to="" omit="" imaging="" tests="" and="" anticoagulant="" treatment="" in="" such="" patients.="" pregnant="" women="" or="" patients="" with="" previous="" vte="" should="" be="" referred="" for="" imaging.="" when="" in="" doubt="" treat="" the="" patient,="" not="" the="" d-dimer="">

Dr Frank Rugman, consultant clinical haematologist, Lancashire Teaching Hospitals NHS Trust, and associate lecturer, Open University

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