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3. Kids Are Not Little Adults: Pediatric Considerations in the Hemostasis/Thrombosis Laboratory
4. Presentation

Abstract

D-dimer in kids versus adults - how can we improve testing algorithms and laboratory test utilization?

Catherine Hayward, McMaster University, Hamilton, Canada

Introduction: D-dimers are produced by lysis of factor XIII cross-linked fibrin. D-dimer tests are the third most frequently ordered coagulation test. In both adults and children, D-dimer levels are evaluated for a number of reasons, including for suspected disseminated intravascular coagulation (DIC) and suspected venous thromboembolic events (VTE), and for adults, a low D-dimer level is used to exclude VTE among persons with a low or moderate probability of VTE. Among children, D-dimer levels are also used to assess some inflammatory states.

Methods: Published literature and findings from our recent, retrospective, consecutive-case cohort study on D-dimer utilization among the academic hospitals in Hamilton were reviewed to gain insights on testing algorithms and D-dimer test utilization across the age spectrum.

Results: D-dimer tests are more commonly ordered for adults compared to children (96 vs 4%), often when adults and children are in the emergency department (~60%) and need assessment of suspected VTE (50% for children, 70% for adults). About ~60% of adult and pediatric patients having elevated D-dimer levels, reflecting that many conditions increase thrombin generation and fibrinolysis. Unique to children, ~23% of D-dimer tests are ordered for the evaluation of childhood inflammatory conditions, such as suspected multisystem inflammatory syndrome in children, Kawasaki disease and systemic juvenile inflammatory arthritis, in keeping with recent guideline recommendations for assessing these conditions. There was poor documentation of DIC and VTE likelihood scores. Patients with multiple tests accounted for 15% of D-dimer workload. Some patients evaluated by ≥ five D-dimer determinations, some were being followed for evidence of cytokine storm during chimeric antigen receptor (CAR) T-cell therapy and most of the others, for DIC. At our center, only CART-cell therapy order sets had repeated D-dimer determinations, yet some patients had D-dimer requested often when coagulation tests were repeated, for unclear reasons. Among patients with multiple tests for DIC, most had overt DIC on initial assessment, with declining D-dimer levels over 10-14 days, including patients that died.

Conclusion: VTE and DIC assessment are the most common reasons for D-dimer assessments for children and adults, and there are more uncertainties about appropriate uses of the test for children including for VTE assessment, and for DIC assessment, given the limited information on International Society on Thrombosis and Haemostasis (ISTH)-DIC scores for children. For both adults and children, quality improvement initiatives could improve D-dimer test utilization, including the documentation of relevant DIC and VTE likelihood scores. There is also a need to discourage inappropriate D-dimer test utilization, and address unnecessary repeat testing as patients with multiple tests accounted for ~15% of our total D-dimer workload.