Pattern of Platelet Recovery in Predicting Outcome in Heparin-Induced Thrombocytopenia and Thrombosis.
Authors: Sabnani Indu , Khan Ajaz , Tsang Patricia 
Published: April 2020

Abstract
Heparin-induced thrombocytopenia and thrombosis (HITT), a severe immune-mediated drug reaction, is often underdiagnosed. Early management of HITT with alternative anticoagulants can result in a favorable outcome. However, the morbidity and mortality associated with HITT remain high, posing challenges for patient management. We describe the clinical profile and pattern of platelet count recovery in a cohort of 34 patients diagnosed with HITT. This retrospective study consists of 164 patients screened for HITT over 18 months at our institution based on positive platelet factor 4 (PF4) IgG antibodies in the proper clinical setting. Patients who tested positive were divided on the basis of recovery of platelet count (increase to &gt;100 × 109/L or by 1.5-fold by day 5 of diagnosis) into two groups: delayed and normal recovery. Of the 164 patients screened, 107 were admitted with cardiac diseases while 57 non-cardiac conditions. A total of 34 patients (21%) were tested positive for PF4 antibodies. Patients with underlying cardiac conditions were more likely to be diagnosed with HITT than non-cardiac patients (28% versus 7%, p=0.0012). The male to female ratio was 1:1.1, and the median age was 65 years. Nineteen of 34 patients (56%) had delayed platelet recovery, while the remaining 15 patients (44%) had normal platelet recovery by day 5. The mortality rate was 68% (13 of 19) in the delayed recovery group, compared to only 7% (1 of 15) in the normal recovery group (p=0.0004). Twelve of the 34 patients with liver dysfunction had delayed platelet recovery and died (figure 1). There were 6 venous and 5 arterial thrombotic episodes. A total of 13 patients (38%) were treated with Argatroban, a direct thrombin inhibitor (DTI) indicated for the treatment of HITT, but it did not seem to improve platelet recovery (Table 1). Eight of the 13 treated patients (62%) and 11 of the 21 untreated patients (52%) showed no platelet recovery by day 5. In conclusion, early diagnosis of HITT is critically important for patient management, and yet, diagnosis is often elusive due to a general lack of awareness of this condition. Underlying cardiac diseases appear to predispose patients to HITT, probably due to previous exposure and sensitization to heparin. Despite the availability of new anticoagulants, HITT remains an undertreated and highly fatal condition with overall mortality of 38% in our series. Underlying liver dysfunction appears to be associated with delayed platelet recovery and poor survival. Affect of DTI on platelet recovery needs to be further investigated. Optimal response to therapy requires early diagnosis and intervention. Further studies are necessary to enhance our understanding of this devastating condition to facilitate early diagnosis and proper treatment.
Treatment and Survival of HITT Patients Outcome Treated with DTI Not treated Total Dead 6 7 13 Alive 7 14 21 Total 13 21 34 Pattern of Platelet Recovery in Patients with HITT with Delyaed Recovery &gt; 5 days Pattern of Platelet Recovery in Patients with HITT with Delyaed Recovery &gt; 5 days Pattern of Platelet Recovery in Patients with HITT with Delyaed Recovery &lt; 5 days Pattern of Platelet Recovery in Patients with HITT with Delyaed Recovery &lt; 5 days