ASH evidence-based guidelines: is the IgG-specific anti-PF4/heparin ELISA superior to the polyspecific ELISA in the laboratory diagnosis of HIT?

You are asked to consult on a 76-year-old man admitted to the hospital with pneumonia and thrombocytopenia. Ten days before the current admission, he had undergone surgery to repair a small bowel obstruction. A preoperative platelet count had been normal. Following surgery, he received subcutaneous unfractionated heparin thromboprophylaxis until his discharge on post-operative day 5. In your differential diagnosis for the patient's thrombocytopenia, you consider heparin-induced thrombocytopenia (HIT) and wish to order laboratory testing. In addition to a polyspecific anti-PF4/heparin ELISA for the diagnosis of HIT, your laboratory has recently begun to offer an IgG-specific ELISA. You wonder which of these assays performs better in the diagnosis of HIT.