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). 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 (Thrombocytopenia, Timing of onset, Thrombosis, oTher cause).5
Another diagnostic challenge is that antibodies may be identified in patients with little or no clinical symptomatology.