Validation of two age dependent D-dimer cut-off values for exclusion of deep vein thrombosis in suspected elderly patients in primary care: retrospective, cross sectional, diagnostic analysisBMJ 2012; 344 doi: https://doi.org/10.1136/bmj.e2985 (Published 06 June 2012) Cite this as: BMJ 2012;344:e2985
- Henrike J Schouten, resident in geriatrics12,
- H L (Dineke) Koek, geriatrician and clinical epidemiologist2,
- Ruud Oudega, general practitioner1,
- Geert-Jan Geersing, general practitioner1,
- Kristel J M Janssen, clinical epidemiologist1,
- Johannes J M van Delden, professor of medical ethics1,
- Karel G M Moons, professor of clinical epidemiology1
- 1Julius Centre for Health Sciences and Primary Care, University Medical Centre Utrecht, PO Box 85500, 3508 GA Utrecht, Netherlands
- 2Department of Geriatrics, University Medical Centre Utrecht
- Correspondence to: H J Schouten
- Accepted 22 March 2012
Objective To determine whether the use of age adapted D-dimer cut-off values can be translated to primary care patients who are suspected of deep vein thrombosis.
Design Retrospective, cross sectional diagnostic study.
Setting 110 primary care doctors affiliated with three hospitals in the Netherlands.
Participants 1374 consecutive patients (936 (68.1%) aged >50 years) with clinically suspected deep vein thrombosis.
Main outcome measures Proportion of patients with D-dimer values below two proposed age adapted cut-off levels (age in years×10 μg/L in patients aged >50 years, or 750 μg/L in patients aged ≥60 years), in whom deep vein thrombosis could be excluded; and the number of false negative results.
Results Using the Wells score, 647 patients had an unlikely clinical probability of deep vein thrombosis. In these patients (at all ages), deep vein thrombosis could be excluded in 309 (47.8%) using the age dependent cut-off value compared with 272 (42.0%) using the conventional cut-off value of 500 μg/L (increase 5.7%, 95% confidence interval 4.1% to 7.8%). This exclusion rate resulted in 0.5% and 0.3% false negative cases, respectively (increase 0.2%, 0.004% to 8.6%).The increase in exclusion rate by using the age dependent cut-off value was highest in the oldest patients. In patients older than 80 years, deep vein thrombosis could be safely excluded in 22 (35.5%) patients using the age dependent cut-off value compared with 13 (21.0%) using the conventional cut-off value (increase 14.5%, 6.8% to 25.8%). Compared with the age dependent cut-off value, the cut-off value of 750 μg/L had a similar exclusion rate (307 (47.4%) patients) and false negative rate (0.3%).
Conclusions Combined with a low clinical probability of deep vein thrombosis, use of the age dependent D-dimer cut-off value for patients older than 50 years or the cut-off value of 750 μg/L for patients aged 60 years and older resulted in a considerable increase in the proportion of patients in primary care in whom deep vein thrombosis could be safely excluded, compared with the conventional cut-off value of 500 μg/L.
Contributors: HJS, HLK, and GJG participated in the study concept and design, analysis and interpretation of data, and drafting of the manuscript. RO acquired the data. RO and KJMJ participated in the study concept and design, analysis and interpretation of data, and critical revision of the manuscript. KGMM and JJMD participated in the study concept and design, analysis and interpretation of data, critical revision of the manuscript, and study supervision. All authors are guarantors of the work. All authors participated in the revision and final approval of the manuscript, and had full access to the data of the study.
Funding: The study received financial support from the Netherlands Organization for Scientific Research (ZonMw project numbers 17088-2502, 917-46-360, and 945-04-009). The funding source had no influence on any aspect of this study.
Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: support from the Netherlands Organization for Scientific Research; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.
Ethical approval: Not required.
Data sharing: No additional data available.
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