Age-adjusted D-dimer excludes pulmonary embolism and reduces unnecessary radiation exposure in older adults: retrospective study

Nobes, J., Messow, C.-M. , Khan, M., Hrobar, P. and Isles, C. (2017) Age-adjusted D-dimer excludes pulmonary embolism and reduces unnecessary radiation exposure in older adults: retrospective study. Postgraduate Medical Journal, 93(1101), pp. 420-424. (doi:10.1136/postgradmedj-2016-134552) (PMID:27941007)

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Abstract

Background Patients in whom a diagnosis of pulmonary embolism (PE) is suspected and whose D-dimers are elevated frequently require CT pulmonary angiogram (CTPA) for diagnosis. Because D-dimer rises with age, an age-adjusted D-dimer threshold may prevent unnecessary radiation exposure from CTPA in older patients.Objective To determine the efficacy and safety of implementing an age-adjusted D-dimer threshold to exclude PE.Design, settings and patients Retrospective comparison of conventional and age-adjusted D-dimer thresholds in 1000 consecutive patients who had both D-dimer and CTPA.Main outcome measures Conventional and age-adjusted D-dimer thresholds for excluding PE were <250 ng/mL and 5× age for patients older than 50 years, respectively. We defined patients as unlikely to have PE using the revised Geneva score (RGS) and two different categories of clinical risk: RGS ≤5 and RGS ≤10.Results We diagnosed PE by CTPA in 244 (24.4) patients. 3/86 patients (3.5) whose D-dimer was below the conventional threshold of 250 ng/mL had PE (RGS 3, 9 and 14), all of which were judged to be light clot load (group 1). 3/108 patients (2.8) whose D-dimer lay between 250 ng/mL and the age-adjusted threshold had PE (RGS 6, 8 and 9), all of which were again judged to be light clot load (group 2). 62/108 group 2 patients with RGS ≤5 were considered unlikely to have PE as were 102/108 using the RGS clinical risk category ≤10. None of the 62 patients with RGS ≤5 had PE while 3/102 patients with RGS ≤10 had PE. 236/806 patients (29.3) whose D-dimer was above the age-adjusted threshold had PE (group 3).Conclusions In a consecutive series of 1000 patients, an RGS ≤5 and an age-adjusted D-dimer would have led to 62 fewer CTPA at a cost of no missed PEs.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Isles, Dr Christopher and Messow, Ms Claudia-Martina
Authors: Nobes, J., Messow, C.-M., Khan, M., Hrobar, P., and Isles, C.
College/School:College of Medical Veterinary and Life Sciences > Institute of Health and Wellbeing > Robertson Centre
College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing
Journal Name:Postgraduate Medical Journal
Publisher:BMJ Publishing Group
ISSN:0032-5473
ISSN (Online):1469-0756
Published Online:09 December 2016
Copyright Holders:Copyright © 2016 The Authors
First Published:First published in Postgraduate Medical Journal 93(1101):420-424
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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