see also: [[Pulmonary Embolism]], [[DVT]], [[Aortic dissection]], [[Pregnancy-Adapted YEARS algorithm]] [LITFL d dimer](https://litfl.com/dealing-with-d-dimer-debacles/) > note: some overlap in the [[PE clinical prediction scores]] article # What is a D-dimer? - Cross-linked fibrin derivates that are the product of plasmin-mediated fibrinolytic degredation - ==markers of fibrinolytic activity==, activation of coagulation - D dimer test uses antibodies to D dimer molecule - ​cleared by renal excretion and ​uptake into reticuloendothelial system - ​half life 8 hours ![[Pasted image 20230731231503.png]] # Levels higher levels correlate with ↑ probability of VTE - 1000-2000 ng/mL odds ratio 2.0 - 2000-4000 odds ratio 4 - \> 4000 odds ratio 9 ==Normal is <250 ng/mL== threshold for dx DVT or PE usually >500 ng/mL (more on this...) # False negatives of D-dimer - heparin therapy - reduces D dimer by 40% in 24 hours - older thrombus - levels fall to 25% of initial value in 10 days - very small thrombus - unlikely to be clinically significant - defective firbinolysis # False positives of D-dimer - Age - cigarette smoking - functional impairment - post-op - pregnancy - race (eg Africa americans) # Pathology besides PE a/w ↑ D-dimer - ACS - upper GI hemorrhage - [[Aortic dissection]] - AF - consumptive coagulopathy [[Snakebite#Coagulopqthy, VICC]], [[DIC]] - Infection/sepsis - Malignancy - [[Pre-eclampsia]] - [[Sickle Cell Anaemia]] - [[Stroke|CVA]] - trauma - superficial thrombophlebitis # Wells score | | | |---|---| |Clinical signs of DVT | 3.0| |no alternative more likely than PE|3.0| |Pulse >100 at rest | 1.5| |immobilised >3 days|1.5| |prior PE/DVT|1.5| |haemopytsis|1| |current/recent cancer|1| **Low -** <2 (try and use PERC) **Moderate -** 2-6 (D dimer if 4 or less) **High -** >6 # PERC [original article](https://pubmed.ncbi.nlm.nih.gov/15304025/) Age >50 HR >100 O2 <95% RA unilateral leg swelling Haemoptysis recent trauma or surgery **Mnemonic:** HAD CLOTS H - hormone (estrogen) use A - age > 50 D- DVT or PE history C- Coughing up blood L - leg swelling (unilateral) O - O2 sats <95% T - Tachycardia > 100bpm S - surgery or trauma (recent # YEARS - clinical signs of DVT - haemoptysis - alternative diagnosis less likely than PE if all no, then D-dimer <1000. Otherwise D-dimer <500. However, in validation study, the subjective question "are alternative diagnoses less likely than PE?" achieved the same result ## Pregnancy adapted YEARS 512 pregnant women imaging not indicated for 65% of woman in 1st trimester, but only 32% in 3rd trimester # Radiation exposure for mother and fetus ![[Pasted image 20230801111844.png]] # Age adjusted D-dimer age in years x 10 ng/mL # When to order d-dimer ![[Pasted image 20230731231628.png]] ## PE - Wells <2 and PERC 0 - very unlikely PE - Wells <2 + normal D-dimer (regardless of PERC) - very unlikely PE - Wells 2-6 and normal D-dimer - PE very unlikely ## Aortic dissection aortic dissection score <1 and normal d-dimer makes dissection unlikely # Related Questions ## pulmonary embolis - [ ] 36Q: [PE](x-devonthink-item://1A14F7A1-E434-47A6-BC68-AF2DD1A7C090?page=8) -- [Answer](x-devonthink-item://736EC9CD-AC9C-4588-BA1E-F4AD190CBA47?page=31) - [ ] 37Q: [Pulmonary embolis](x-devonthink-item://554C45F7-8661-4467-BD61-8A79B6ECABF4?page=88) -- [Answer](x-devonthink-item://554C45F7-8661-4467-BD61-8A79B6ECABF4?page=89) ## pulmonary embolism - [ ] 38Q: [Pulmonary Embolis](x-devonthink-item://B9C99BB4-DAF8-4D15-BBD3-40E82B279902?page=16) -- [Answer](x-devonthink-item://DF848F67-27AB-450A-988B-159784B72957?page=16) - [ ] 39Q: [Post Arrest ECG](x-devonthink-item://C4CCEB12-61D5-4308-AA41-5078F3D96CC0?page=13) -- [Answer](x-devonthink-item://75D8E35B-EE77-4D1B-A665-438451C976AE?page=18) -- [prop](x-devonthink-item://E34679F3-102F-4E16-AF81-9D679412EDAC?page=11) - [ ] 40Q: [Pulmonary Embolism](x-devonthink-item://1EA9311E-0B9E-49F7-8D6E-4C4187A838C4?page=61) -- [Answer](x-devonthink-item://B1CB2E8F-5D04-49EE-8274-043871389D28?page=39)