Age adjusted D-dimer
Background
- The PE derivation and validation study for usage of the age adjusted d-dimer formula concluded that when combining the d-dimer adjustment with clinical probability, less patients required CTA for exclusion and offered no clinical increase in the rate of missed Pulmonary embolism[1][2]
- Similarly, using the age adjusted d-dimer in combination with clinical probability can reduce the need for further testing in DVT evaluations with no substantial risk to patient safety[3][4][5]
Usage
Labs commonly report the test as fibrinogen equivalent units (FEUs) with the cutoff at 500 ng/mL and most studies used the FEU values for derivation or validation. If reported by the lab as a D-dimer unit (DDU) the cutoff is often 230 ng/mL. 2 FEUs equal 1 DDU.
- Age (years) x 10 ug/L for patients > 50 years of age
- Patient age 75 = age adjusted d-dimer of 750 ug/L
- If using a lab with a cutoff of 230 (DDU assay) then formula is Age x 5
| TEST | Age | Sensitivity | Specificity |
| Lab cutoff | 51 - 60 | 100% | 57.60% |
| Lab cutoff | 61 - 70 | 99.00% | 39.40% |
| Lab cuttoff | 71 - 80 | 98.70% | 24.50% |
| Lab cutoff | >80 | 99.60% | 14.70% |
| Age Adjusted cutoff | 51 - 60 | 99.40% | 62.30% |
| Age Adjusted cutoff | 61 - 70 | 97.30% | 49.50% |
| Age Adjusted cutoff | 71 - 80 | 97.30% | 44.20% |
| Age Adjusted cutoff | >80 | 97.00% | 35.20% |
Special Considerations
- Risk stratification for all patients should take place using the Wells Criteria
- Know your lab's assay cutoff and whether it is report as DDU or FEUs since the formula is different for the different assays
See Also
References
- ↑ Douma R. et al. Potential of an age adjusted D-dimer cut-off value to improve the exclusion of pulmonary embolism in older patients: a retrospective analysis of three large cohorts. BMJ (Clinical research ed.) (March 30). 2010. doi:10.1136/bmj.c1475.
- ↑ Douma, R. et al. Using an age-dependent D-dimer cut-off value increases the number of older patients in whom deep vein thrombosis can be safely excluded. Haematologica, no. 10 (April 17). 2012. doi:10.3324/haematol.2011.060657.
- ↑ Schouten, H et al.. Diagnostic accuracy of conventional or age adjusted D-dimer cut-off values in older patients with suspected venous thromboembolism: systematic review and meta-analysis. BMJ (Clinical research ed.) (May 3). 2013. doi:10.1136/bmj.f2492.
- ↑ Schouten, H et al. 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 analysis. BMJ (Clinical research ed.) (June 6). 2012. doi:10.1136/bmj.e2985.
- ↑ Adams, D, et al. Clinical utility of an age-adjusted D-dimer in the diagnosis of venous thromboembolism. Ann Emerg Med. 2014; 64:232-234.