Thread by @Rheumat_Aravind

🧵D-Dimer – Diagnostic Hero or Misleading Villain?

We’ve all ordered D-Dimer.
But do we really understand what it’s telling us?
Let’s break down when D-Dimer helps—and when it just adds confusion👇
@IhabFathiSulima @DrAkhilX @drkeithsiau @CelestinoGutirr @Janetbirdope @nirmalregency @Lupusreference #MedTwitter #NEETPG

1. What is D-Dimer, really?

🧬 It’s a fibrin degradation product.
If you see it, it means the body formed and broke down a clot.

But: That doesn’t always mean pathology.

2. When is it actually useful?

✅ Low to moderate suspicion of DVT/PE
🧠 It’s a rule-out tool
Normal D-Dimer? Great.
Abnormal? Don’t panic yet.

3. D-Dimer can go up for tons of reasons:

– Age > 50
– Surgery, trauma
– Infections, cancer
– Pregnancy
– SLE, vasculitis
– COVID-19
– Hospital admission itself!

4. Rheumatology trap: Flare or clot?

SLE patient with leg pain + raised D-Dimer?

🔍 Check pretest probability
🔄 If low → duplex or imaging
💡 Don’t anchor on D-Dimer alone

5. What’s an age-adjusted D-Dimer?

🧓 After age 50, D-Dimer naturally rises.
So we adjust:
Age × 10 ng/mL (FEU) = cutoff

E.g. Age 72 → cutoff is 720

6. How NOT to use D-Dimer:

🚫 High suspicion? Go straight to imaging.
🚫 As a standalone test.
🚫 To monitor clot burden.
🚫 In inflammatory diseases to predict thrombosis without clinical context.

7. D-Dimer in COVID, APS, MAS?

🔴 High D-Dimer = clot risk, cytokine storm, endothelial damage
BUT: Use clinical correlation.
Don’t treat numbers in isolation.

📌 Takeaway

D-Dimer is powerful in the right clinical context.
Don’t let it become a diagnostic distraction.
Use it to rule out, not stress out.