WHAT'S NEW?: We can now make use of the D-dimer in older patients
Up until now, it was acknowledged that the simple and less expensive D-dimer test was less useful for our older patients. In fact, in their 2007 clinical practice guideline on the diagnosis of VTE in primary care, the American Academy of Family Physicians and the American College of Physicians commented on the poor performance of the test in older patients.2 A more recent guideline—released by the Institute for Clinical Systems Improvement in January 2013—provided no specific guidance for patients over age 50.7 The meta-analysis reported on here, however, provides that guidance: Using an age-adjusted D-dimer cutoff improves the diagnostic accuracy of D-dimer screening in older adults.
CAVEATS: Results are not generalizable to patients at higher risk
These findings are not generalizable to all patients, particularly those at higher clinical risk who would undergo imaging regardless of D-dimer results. Not all patients included in this meta-analysis whose D-dimer was negative received imaging to confirm that they did not have VTE. As a result, the diagnostic accuracy of using an age-adjusted cutoff could have been overestimated, although this is likely not clinically important because these cases would have remained symptomatic within the 45-day to 3-month follow-up period.
CHALLENGES TO IMPLEMENTATION: You, not the lab, will need to do the calculation
One of the more valuable aspects of this study is it identifies a simple calculation that can directly improve patient care. Physicians can easily apply an age-adjusted D-dimer cutoff as they interpret lab results by multiplying the patient’s age in years × 10 mcg/L. While this does not require institutional changes by the lab, hospital, or clinic, it would be helpful if the age-adjusted D-dimer calculation was provided with the lab results.
Acknowledgement
The PURLs Surveillance System was supported in part by Grant Number UL1RR024999 from the National Center for Research Resources, a Clinical Translational Science Award to the University of Chicago. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center for Research Resources or the National Institutes of Health.
