PF4 and susceptibility to pneumonia measurement: A representative case illustrates this challenge: one patient developed life-threatening massive pleural effusion (secondary to pneumonia and pulmonary edema) compounded by iatrogenic thrombocytopaenia, a condition commonly resulted by HIT (Heparin Induced Thrombocytopaenia)—an immune-mediated prothrombotic disorder caused by anti-PF4/heparin antibodies (38).