Usefulness of a novel method for the screening of deep vein thrombosis by using a combined D-dimer- and age-based index before total hip arthroplasty

Plasma D-dimer level is clinically useful for diagnosing patients with suspected deep vein thrombosis (DVT). However, the cut-off value for the D-dimer level remains controversial and undetermined with regard to total hip arthroplasty (THA). The objective of this study was to estimate the efficacy of an age- and D-dimer-based index for diagnosing DVTs in asymptomatic cases before THA. We enrolled 224 patients with no symptoms associated with DVT before THA. All the patients underwent ultrasonography, and the plasma D-dimer level was recorded about 1 month preoperatively. The optimal cut-off value was calculated using multiple logistic regression and receiver operating curve analyses. DVTs were detected in 13 patients (5.8%) using ultrasonography. Multiple logistic regression analysis demonstrated that age (odds ratio [OR]: 1.13; p = 0.007) and D-dimer value (OR: 1.74; p = 0.003) were related to the existence of preoperative DVT. A DVT index (0.12 × age + 0.45 × the D-dimer value) of 8.15 was the most reasonable cut-off value according to the receiver operating curve analysis. This value caused 100% sensitivity and 70.1% specificity, with an area under the curve (AUC) of 0.905 (range, 0.836-0.975). For age and D-dimer value, the AUCs were 0.828 (0.749-0.907) and 0.716 (0.522-0.910), respectively. This study demonstrated that age and D-dimer index can be useful in screening patients for DVTs before THA. This DVT index is also easy to calculate and may be clinically significant.