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Platelet transfusions associated with increased risk for death in HIT, TTP
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Platelet transfusions are frequently used in patients with thrombotic thrombocytopenic purpura, immune thrombocytopenic purpura and heparin-induced thrombocytopenia, according to study results.
However, use of platelet transfusions in patients with thrombotic thrombocytopenic purpura (TTP) and heparin-induced thrombocytopenia (HIT) was associated with an increased risk for arterial thrombosis and mortality, results showed.
Aaron Tobian
“Because these conditions are so rare, they’re difficult to study,” researcher Aaron Tobian, MD, PhD, associate professor of pathology at Johns Hopkins University School of Medicine, said in a press release. “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 [immune thrombocytopenic purpura (ITP)], [heparin-induced thrombocytopenia] HIT and TTP, and that they’re associated with higher odds of arterial blood clots and mortality in TTP and HIT.”
Tobian and colleagues used 2007 to 2011 data from the Nationwide Inpatient Sample to evaluate risks associated with platelet transfusions.
Researchers identified 10,624 patients hospitalized with TTP, 6,332 hospitalized with HIT and 79,980 hospitalized with ITP. Most patients with TTP were female (66.6%), whereas a majority of patients with ITP (56.6%) and HIT (51.3%) were male. Children accounted for 1.9% of the TTP cohort, 0.5% of the HIT cohort and 20.9% of the ITP cohort.
Platelet transfusions were used in 25.8% of ITP cases, 10.1% of TTP cases and 7.1% of HIT cases. Significantly more adults than children received platelet transfusions (P˂.01).
Analyses adjusted for age and gender indicated the use of platelet transfusions in patients with TTP was associated with an increased risk for arterial thrombosis (OR=5.8; 95% CI, 1.3-26.6) and mortality (OR=2; 95% CI, 1.3-3). These analyses also indicated an increased risk for acute myocardial infarction with platelet transfusions in TTP (OR=2; 95% CI, 1.2-3.3); however, this risk lost its significance in analyses adjusted for clinical severity and acuity.
Adjusted analyses also indicated platelet transfusions were associated with an increased risk for arterial thrombosis (OR=3.4; 95% CI, 1.2-9.5) and mortality (OR=5.2; 95% CI, 2.6-10.5) in patients with HIT.
Researchers noted platelet transfusions were not associated with a risk for venous thrombosis, and there were no increased risks among patients with ITP.
“Our analysis found no significantly increased risks from platelet transfusions in ITP,” researcher Ruchika Goel, MD, MPH, clinical fellow in pediatric hematology oncology at The Johns Hopkins Hospital, said in the release. “But in TTP, a platelet transfusion increased the odds of a potentially lethal arterial blood clot more than fivefold and doubled the odds of a heart attack.”
The platelet disorder may not have been apparent in some of the patients until after they experienced side effects from the transfusion, Tobian said in the release.
“In other cases, it may be used as the treatment of last resort in the very sickest patients,” he added.
Therefore, it may be hard to determine a causal relationship.
“Whether the platelet transfusions were directly responsible for these events or they serve as a surrogate marker for severity of illness cannot be absolutely determined,” Goel and colleagues wrote. “However, the results remained significant after adjusting for clinical severity/acuity. Until mechanistic studies or trials are available to demonstrate the efficacy and risks of platelet transfusions in TTP and HIT, platelets should be considered to be relatively contraindicated and use only for emergencies, invasive procedures, surgeries, or severe or life-threatening bleeding refractory to other therapies.”
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Christopher C. Silliman, MD, PhD
Goel and colleagues have presented convincing evidence that platelet transfusion is associated with pathological thrombogenesis in patients with consumptive or destructive platelet disorders. Specifically, platelet transfusions given to patients with thrombocytopenic purpura (TTP) were associated with arterial thrombi, acute myocardial infarction and in-hospital mortality; transfusions given to patients with heparin-induced thrombocytopenia (HIT) were associated with arterial thrombi and in-hospital mortality; and transfusions given to patients with immune thrombocytopenic purpura (ITP) were not associated with an increase in thrombogenic sequelae nor in-hospital mortality. Using 5 years of the Nationwide Inpatient Sample, platelet transfusions were reported in 10.1% of TTP from 10,624 admissions, 7.1% of HIT from 6,332 admissions, and 25.8% of ITP from 79,980 admissions. For TTP patients, the adjusted ORs were 5.8 for arterial thrombosis (95% CI, 1.3-26.6), 2 for acute MI (95% CI, 1.2-3.3) and 2 for mortality (95% CI, 1.3-3). For HIT patients, the adjusted ORs were 3.4 for arterial thrombosis (95% CI, 1.2-9.5) and 5.2 (95% CI, 2.6-10.5) for mortality. Except for MI, the association between platelet transfusion and arterial thrombosis and in-hospital mortality remained significant after adjusting for clinical severity and acuity, age and gender. Neither TTP nor HIT was associated with venous thromboembolic events. Until now, most clinicians have mostly relied upon expert opinion to guide management of these patients with regard to platelet transfusion due to the relative paucity of evidence-based guidelines. There are no data supporting prophylactic platelet transfusions for TTP, HIT or ITP, and platelet transfusion should be limited to those patients with significant clinical bleeding. Thus, if a platelet transfusion is not clinically indicated, it is contraindicated and the clinician should “treat the patient, not the platelet count.”
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