What does a high d-dimer quant count mean?

Many, many things : D-dimer is a protein that is formed when the body's clotting system has been activated. Unfortunately, there are a very vast number of things and conditions that can cause an elevation in the d-dimer. These can range from blood clots to infections to trauma. So, a simply elevated d-dimer does not do a good job at making an accurate diagnosis.

Depends on disease: D-dimer is usually not requested unless there is a work up to do to establish the yes or no diagnosis of DVT or pe (clots in leg or arm) or dic in sepsis. It should not be used to make an unknown diagnosis as it can be elevated in many inflammatory conditions. In the above clots or dic if elevated it helps point to a yes diagnosis, then full work up still has to be done. It gives reason to proceed.