Harper P L, Theakston E, Ahmed J, Ockelford P
Department of Haematology, Palmerston North Hospital, Palmerston North, New Zealand.
Intern Med J. 2007 Sep;37(9):607-13. doi: 10.1111/j.1445-5994.2007.01388.x. Epub 2007 Jun 2.
The D-dimer assay is used as an exclusion test in the assessment of suspected venous thromboembolic disease; patients with a negative result have a low probability of thrombosis. We reviewed the D-dimer results from a hospital and community laboratory using the vidas D-dimer test to assess the influence of age on the D-dimer assay.
D-dimer results from 6631 unselected patients aged more than 16 years were analysed in four age groups and it was shown that the median D-dimer concentration increased with age (16-40 years, 294 ng/mL; 40-60 years, 387 ng/mL; 60-80 years; 854 ng/mL; >80 years, 1397 ng/mL). To test the effect of age on the assay specificity, a cohort of 1897 patients with suspected venous thromboembolic disease was analysed separately. Patients with a negative D-dimer were discharged without further investigation. Patients with a positive result and a clinical suspicion of thrombosis underwent further investigation. One hundred and sixty-five deep vein thrombosis or pulmonary embolus cases were identified.
The assay specificity decreased with age from 70% in patients less than 40 years to below 5% in patients more than 80 years. Receiver operator curves were prepared for each age group and the effect of altering the threshold value was analysed. In patients 60-80 years old a threshold value of 1000 ng/mL increased assay specificity to 55% without loss of assay sensitivity.
The vidas D-dimer assay with a threshold value of 500 ng/mL has little clinical value as an exclusion test in patients more than 80 years old. The assay specificity is poor (26%) in patients aged 60-80 years but could be improved by increasing the threshold value to 1000 ng/mL. We believe that this should be tested in a prospective trial.
D-二聚体检测用作疑似静脉血栓栓塞性疾病评估中的排除试验；检测结果为阴性的患者发生血栓形成的可能性较低。我们回顾了一家医院和社区实验室使用维达D-二聚体检测得出的结果，以评估年龄对D-二聚体检测的影响。
对6631例年龄超过16岁的未经过挑选的患者的D-二聚体结果进行了分析，分为四个年龄组，结果显示D-二聚体浓度中位数随年龄增长而升高（16 - 40岁，294 ng/mL；40 - 60岁，387 ng/mL；60 - 80岁，854 ng/mL；>80岁，1397 ng/mL）。为检测年龄对检测特异性的影响，对1897例疑似静脉血栓栓塞性疾病的患者队列进行了单独分析。D-二聚体检测结果为阴性的患者无需进一步检查即可出院。检测结果为阳性且临床怀疑有血栓形成的患者接受进一步检查。共确诊165例深静脉血栓形成或肺栓塞病例。
该检测的特异性随年龄增长而降低，小于40岁的患者中为70%，大于80岁的患者中则低于5%。为每个年龄组绘制了受试者工作特征曲线，并分析了改变阈值的影响。在60 - 80岁的患者中，阈值设定为1000 ng/mL时，检测特异性提高到55%，且检测敏感性未降低。
对于80岁以上的患者，阈值为500 ng/mL的维达D-二聚体检测作为排除试验几乎没有临床价值。在60 - 80岁的患者中，该检测的特异性较差（26%），但将阈值提高到1000 ng/mL可使其得到改善。我们认为这应该在前瞻性试验中进行验证。
