Which test measures fibrin split products and helps rule out PE or DVT?

• A. D-Dimer
• B. WBC
• C. CMP
• D. HCG

Answer: (A)

D-dimer measures fibrin degradation products that appear when a clot is formed and then broken down by the body's fibrinolytic system. In patients with suspected DVT or PE, a negative result is very useful because it strongly suggests there isn’t clinically significant thrombosis, especially when the pretest probability is low to intermediate. This makes it a good rule-out test, potentially sparing the patient from unnecessary imaging. However, a positive result isn’t specific to DVT or PE and can occur with many conditions such as recent surgery, infection, pregnancy, liver disease, or inflammation, so further testing is usually needed to confirm a clot. The other tests listed do not assess clot formation or breakdown: WBC can indicate infection or inflammation, CMP checks organ function and electrolytes, and HCG indicates pregnancy.