Not so fast to debunk age-adjusted D-dimer

Short Attention Span Summary

Funny math
These authors found the diagnostic performance of D-dimer did not change using an age-adjusted strategy (if >50 years, D-dimer = age x 10).  But here's why.  This is not at all clear in the abstract.  They used the mean D-dimer for the whole batch of frozen samples, and that was a D-dimer of 620.  So compared to that, the age-adjusted D-dimer had the same diagnostic accuracy, i.e. NPV, PPV, sensitivity, and specificity.

Spoon Feed
You may hear about this study and conclude that age-adjusted D-dimer does not improve diagnostic accuracy.  But this is not the study to tell us that.  I plan to continue using a D-dimer level of age x 10 in patients over 50.

R.E.B.E.L. EM has an excellent review of age-adjusted D-dimer.


Abstract

J Thromb Haemost. 2016 Jul 25. doi: 10.1111/jth.13424. [Epub ahead of print]

Questioning Use of an Age-Adjusted D-Dimer Threshold to Exclude Venous Thromboembolism: Analysis of Individual Patient Data from Two Diagnostic Studies.

Takach Lapner S1,2, Julian JA3, Linkins LA1,4, Bates SM1,4, Kearon C1,4.

Author information:

1Department of Medicine, McMaster University, 1280 Main Street West, Hamilton, ON, Canada, L8V 4K1.

2Department of Medicine, University of Alberta, 4-112 Clinical Sciences Building, 11350 83 Avenue, Edmonton, AB, Canada, T6G 2R3.

3Ontario Clinical Oncology Group Juravinski Hospital, G Wing 1st floor, 711 Concession St, Hamilton, ON, Canada, L8V 1C3.

4Thrombosis and Atherosclerosis Research Institute, McMaster University, 237 Barton Street East, Hamilton, Ontario, Canada, L8L 2X2.

Abstract

BACKGROUND:

Using a progressively higher D-dimer level to exclude venous thromboembolism (VTE) with increasing age has been proposed but is not well validated.

OBJECTIVE:

To determine if it is appropriate to use a progressively higher D-dimer level to exclude VTE with increasing age.

PATIENTS/METHODS:

We analyzed clinical data and blood samples from 1649 patients with a first suspected deep vein thrombosis or pulmonary embolism. We compared the negative predictive value (NPV) for VTE, and the proportion of patients with a negative D-dimer result, using three D-dimer interpretation strategies: a progressively higher D-dimer threshold with increasing age ("Age-adjusted strategy"); the same higher D-dimer threshold in all patients ("Mean D-dimer strategy"); and a progressively higher D-dimer threshold with decreasing age ("Inverse age-adjusted strategy").

RESULTS:

The NPV with the Age-adjusted strategy (99.6%; 95% confidence interval [CI] 99.0 to 99.9%) was not different from that of the Mean D-dimer strategy (99.7%; 95% CI, 99.0 to 99.9%) or the Inverse age-adjusted strategy (99.8%; 95% CI, 99.1 to 99.9%). The proportion of patients with a negative result with the Age-adjusted strategy (50.9%; 95% CI, 48.5 to 53.4%) was not different from that of the Mean D-dimer strategy (51.7%; 95% CI, 49.3 to 54.1%) or the Inverse age-adjusted strategy (49.5%; 95% CI, 47.1 to 51.9%).

CONCLUSIONS:

Our analysis does not support use of a progressively higher D-dimer level to exclude VTE with increasing age. This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved.

PMID: 27455175 [PubMed - as supplied by publisher]

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