Normal D-dimer Value
The normal D-dimer value is less than 0.5 μg/mL (500 ng/mL), with values above this threshold considered elevated and requiring clinical interpretation based on the patient's age and clinical context. 1
Standard Reference Range
- The universally accepted upper limit of normal for D-dimer is <0.5 μg/mL or <500 ng/mL, which serves as the standard cutoff for ruling out venous thromboembolism in low-risk patients 1, 2
- This threshold has been validated across multiple studies with a sensitivity of 96.3-99.5% for detecting pulmonary embolism when used as an exclusion test 2, 3
- Values below this cutoff allow safe exclusion of PE in approximately 29-31% of outpatients with suspected thromboembolism 2, 3
Age-Adjusted Cutoffs for Improved Specificity
- For patients over 50 years of age, an age-adjusted cutoff (age × 10 ng/mL) should be used to improve specificity while maintaining sensitivity above 97% 1
- Standard cutoffs lose clinical utility with advancing age, as D-dimer specificity decreases to only 10% in patients over 80 years old 1, 4
- The median D-dimer concentration increases progressively with age: 294 ng/mL in patients 16-40 years, 387 ng/mL in patients 40-60 years, 854 ng/mL in patients 60-80 years, and 1397 ng/mL in patients over 80 years 4
- Age-adjusted cutoffs can increase the proportion of patients in whom PE can be safely excluded from 6.4% to 30% without additional false-negative findings 1
Critical Considerations for Interpretation
- D-dimer results must specify the unit type used, as Fibrinogen Equivalent Units (FEU) are approximately two-fold higher than D-dimer Units (DDU), which can cause significant confusion 1
- Different laboratories use different assays with varying sensitivities, specificities, and reference ranges, making cutoff values non-transferable between institutions 1, 5
- The test has high sensitivity but low specificity, meaning elevated values occur in numerous non-thrombotic conditions including pregnancy, recent surgery/trauma, cancer, sepsis, advanced age, and inflammatory states 1, 6
Clinical Application by D-dimer Level
- <0.5 μg/mL (500 ng/mL): Normal range; effectively excludes VTE in low-to-intermediate probability patients with a negative predictive value of 94.4-99% 1, 2, 3
- 0.5-2.0 μg/mL: Mildly elevated; requires correlation with clinical probability and may warrant further investigation 1
- >5.0 μg/mL (>5000 ng/mL): Extremely elevated; 89% of patients have VTE, sepsis, and/or cancer, warranting immediate comprehensive evaluation 6
Special Population Considerations
- Pregnancy: Normal D-dimer levels increase progressively during pregnancy, ranging from 0.11-0.40 μg/mL in the first trimester, 0.14-0.75 μg/mL in the second trimester, and 0.16-1.3 μg/mL (up to 2.0 μg/mL may be normal) in the third trimester 1
- Aortic dissection: D-dimer >0.5 μg/mL has 94-100% sensitivity for acute aortic dissection, though patients with thrombosed false lumens or intramural hematomas may have falsely low levels 7, 1, 8