Our August, 2020 Quick Question asks, “What condition may account for a chronically elevated D-dimer?” We’ve had 59 respondents with a broad distribution of results:
- Plasma human anti-mouse antibody: 7% 
- Rheumatoid factor: 14% 
- Chronic low-grade inflammation: 24% 
- Venous thromboembolic disease: 17% 
- Disseminated intravascular coagulation: 34% 
- Other, please comment: 4% 
George raised this question because we are seeing increasing D-dimer assay volumes in response to its value in Covid monitoring. To be fair, the question had no wrong answer. Human anti-mouse antibody [HAMA] may arise in people who’ve been treated with a drug whose manufacturing process involves mouse cell cultures. This is relatively common, but HAMA rarely interferes with the D-dimer assay, and in fact, many distributors employ a reagent that includes a HAMA neutralizer. Likewise, rheumatoid factor may interfere and create a false positive.
Because D-dimer assays are designed to be sensitive, either chronic or acute low-grade inflammatory conditions elevates the D-dimer result. Consequently, D-dimer assays are often termed “promiscuous.” Because D-dimers rise in most inflammatory conditions, the assay is not used to confirm venous thromboembolic [VTE] disease but rather to rule out thrombosis when symptoms are ambiguous.
Disseminated intravascular coagulation [DIC, consumption coagulopathy] typically associates with a markedly increased D-dimer. Answer 5 is correct, but typically the level is elevated to a point that is unmistakeable.
Thanks to all for your responses, and watch for additional entries dealing with D-dimer testing.