HIT/HITT is a diagnosis that requires both clinical judgment and laboratory corroboration, ie, a clinical, pathologic diagnosis.
Thrombocytopenia in a hospitalized patient is very common and may be due to a vast number of causes (eg, consumption, dilutional effect from fluids or transfusions, drugs, sepsis, splenic sequestration, etc.). For patients exposed to heparin, HIT/HITT is an important consideration, given the life-threatening potential. Applying a standardized and objective approach to the clinical assessment can help determine the pretest probability of HIT/HITT.4 The most common and widely accepted scoring model is called the 4T’s (ASHeducationbook.hematologylibrary.org/content/2003/1/497/F3.expansion.html). Another diagnostic challenge is that antibodies may be identified in patients with little or no clinical symptomatology.