Platelet transfusions may increase the risk of death in patients with platelet consumptive disorders, results of a large study suggest.
Investigators observed a 2-fold increase in the risk of death among patients with thrombotic thrombocytopenic purpura (TTP) who received platelet transfusions and a 5-fold increase among transfused patients with heparin-induced thrombocytopenia (HIT).
There was no increased risk among patients with immune thrombocytopenia (ITP), however.
Aaron Tobian, MD, PhD, of the Johns Hopkins University School of Medicine in Baltimore, Maryland, and his colleagues reported these results in Blood. They were previously presented at the 2014 AABB Annual Meeting.
“Because these conditions are so rare, they’re difficult to study,” Dr Tobian noted. “There was some suggestion that transfusion may be harmful in these conditions, but it really was not known until now.”
“Our study is the first one to show that platelet transfusions are frequently administered to patients with ITP, HIT, and TTP, and that they’re associated with higher odds of arterial blood clots and mortality in TTP and HIT.”
For this study, Dr Tobian and his colleagues analyzed data from the Nationwide Inpatient Sample, a federal database that contains billing records for about 20% of all patients treated and discharged at about 1000 US community hospitals in 47 states.
The database contains information on about 8 million inpatient hospitalizations per year nationwide. The study covered the years 2007 to 2011.
During that time, there were 79,980 hospital admissions for ITP, 10,624 for TTP, and 6332 for HIT. Platelet transfusions were reported in 10.1% of hospitalizations for TTP, 7.1% for HIT, and 25.8% for ITP.
“Our analysis found no significantly increased risks from platelet transfusions in ITP,” said study author Ruchika Goel, MD, also of Johns Hopkins.
“But in TTP, a platelet transfusion increased the odds of a potentially lethal arterial blood clot more than 5-fold and doubled the odds of a heart attack.”
Specifically, in an age- and gender-adjusted analysis, the odds ratio (OR) for arterial thrombosis was 5.8, and the OR for acute myocardial infarction (AMI) was 2.0 in TTP patients who received platelet transfusions. The OR for stroke was 1.6, and the OR for venous thrombosis was 1.1.
Similarly, HIT patients had an increased risk of arterial thrombosis (OR=3.4) and AMI (OR=1.9) if they received a platelet transfusion. But they did not have an increased risk of venous thrombosis (OR=0.8) or stroke (OR=0.5).
Platelet transfusions among ITP patients were not significantly associated with venous thrombosis (OR=1.3), arterial thrombosis (OR=0.3), AMI (OR=1.3), or stroke (OR=1.3) after adjustment for age and gender.
The all-cause, in-hospital mortality rates were 8.8% for TTP patients, 3.4% for HIT patients, and 1.4% for ITP patients.
Patients with TTP and HIT had a significantly increased risk of all-cause mortality if they received platelet transfusions, with age- and gender-adjusted ORs of 2.0 and 5.2, respectively. But platelet transfusions were not significantly associated with mortality in ITP patients, with an OR of 1.1.
The investigators said they were surprised at the prevalence of platelet transfusions in this patient population, in spite of some practitioners’ concerns about the risks.
But Dr Tobian noted that, in some cases, doctors may not know a patient has a platelet disorder until they see the potentially deadly reaction to the transfusion. And in other cases, the transfusion may be used as a last resort.
He and his colleagues believe that, for patients with HIT and TTP, platelet transfusions should be reserved “only for severe, life-threatening bleeding refractory to other therapies or major surgery.”
