From the Guidelines
A D-dimer level of 468 ng/mL is likely normal for a 98-year-old woman. D-dimer levels naturally increase with age, and many laboratories now use age-adjusted cutoffs (calculated as age × 10 ng/mL for patients over 50) 1. For a 98-year-old, an age-adjusted normal threshold would be approximately 980 ng/mL, making 468 well within normal limits. This age adjustment is important because older adults have higher baseline D-dimer levels due to decreased clearance and increased fibrin turnover, even without pathological clotting. Without age adjustment, many elderly patients would have false positive results. However, clinical context remains crucial - if the patient has symptoms suggesting thrombosis (like leg swelling, chest pain, or shortness of breath), further evaluation may still be warranted despite the "normal" D-dimer. The D-dimer test is most useful as a rule-out test when negative, rather than as a diagnostic test when elevated, especially in the elderly.
Key Points
- Age-adjusted D-dimer cutoffs are recommended for patients over 50 years old 1
- For a 98-year-old, the age-adjusted normal threshold would be approximately 980 ng/mL
- A D-dimer level of 468 ng/mL is below this threshold and is likely normal
- Clinical context is important, and further evaluation may be warranted if symptoms suggest thrombosis
Recommendations
- Use age-adjusted D-dimer cutoffs for patients over 50 years old
- Consider clinical context when interpreting D-dimer results
- Further evaluation may be warranted if symptoms suggest thrombosis, even with a "normal" D-dimer result
From the Research
D-Dimer Levels in the Elderly
- D-dimer levels can be elevated in individuals over 80 years old, even in the absence of any underlying disease 2
- This elevation is due to the natural increase in D-dimer levels with age, which can limit the usefulness of D-dimer testing in this population
Interpretation of D-Dimer Results
- A D-dimer level of 468 may not be considered elevated in an absolute sense, but its interpretation depends on the clinical context and the individual's age 2, 3
- In a 98-year-old lady, a D-dimer level of 468 may be considered relatively normal, given the natural increase in D-dimer levels with age
Clinical Considerations
- When interpreting D-dimer results, it is essential to consider the patient's clinical presentation, medical history, and other diagnostic findings 4, 5, 6
- A comprehensive evaluation, including clinical decision rules and imaging studies, may be necessary to rule out venous thromboembolism or other conditions that may be associated with elevated D-dimer levels.