How accurate are d diner tests?

D-dimer: Very specific for a pulmonary embolus or clot, especially when used in conjunction with a Vq scan ( ventilation/perfusion lung scan).

Pretty accurate: I think you mean d-dimer tests. A test which measures the amount of a breakdown product formed when fibrin is broken down. Fibrin is a major part of blood clots. The body has systems which both clot blood and break down the clot. Any test can be 'false.' More information is needed to judge the 'pre-test probability' that basically means- what did you expect and does the result make sense?

Depends: D-Dimer testing for blood clots in the lungs is better at determining that there IS a clot when one really IS present (sensitivity), than in determining that there ISN'T a clot when one ISN'T present (specificity). In other words, it's better at determining that you really DO have a clot than it is at determining that you really DON'T.

Not very: D Dimer tests are sensitive, but not specific. This means you can get a great many false positive tests (abnormal test but no disease present). A positive test means you need more testing (usually ultrasound or CT scan) The D dimer can be useful, in low risk individuals, to rule out the presence of a blood clot (DVT or PE).