Heparin-Induced Thrombocytopenia - Retrospective Analysis of Data on Incidence and Outcomes Study

Study Overview
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Brief Summary
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HIT-RADIO is a study of patients who had a positive heparin PF-4 antibody test between 1/21/2008 and 9/25/2008 at selected hospitals. The study will collect and analyse information that is already in the patients' medical records. Information about laboratory values (such as platelet counts), treatments (such as medications), and outcomes (such as blood clots, amputation, and death) will be included.

Detailed Description
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HIT-RADIO is a retrospective chart-review study of patients who had a positive heparin PF-4 antibody test between 1/21/2008 and 9/25/2008 at selected hospitals associated with the Transfusion Medicine/Hemostasis Clinical Trials Network . Heparin-induced thrombocytopenia (HIT) is a major complication of the administration of heparin and can result in life-threatening thrombosis with or without thrombocytopenia (HIT-T) or can produce thrombocytopenia without clinically symptomatic thrombosis (isolated HIT). Isolated heparin-induced thrombocytopenia is defined as a fall in platelet count associated with a positive heparin PF-4 antibody test, in the absence of clinically overt thrombosis. While the treatment of HIT-T (HIT with thrombosis) with anticoagulation is well established, the risks and treatment of isolated HIT are unclear. It is anticipated that this data analysis will provide a current overview of the implications of a positive heparin PF-4 antibody test in clinical practice. It should determine the percentage of positive heparin PF-4 antibody tests that are associated with thrombocytopenia and thrombosis (HIT-T) or isolated HIT at diagnosis and the subsequent major clinical outcomes of death, limb amputation/gangrene, and new thrombosis. No snapshot of such HIT patients has been conducted in the past decade and the results will be important in assessing the impact of HIT in current medical care as well as documenting current treatment strategies.

Official Title
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Heparin-Induced Thrombocytopenia - Retrospective Analysis of Data on Incidence and Outcomes Study (HIT-RADIO Study)

Conditions
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Heparin Induced Thrombocytopenia

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: All subjects with a positive heparin PF-4 antibody test occurring between 1/21/2008 and 9/25/2008 Medical record available for the admission during which the positive heparin PF-4 antibody test was obtained Exclusion Criteria: None
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Time to Occurrence of a Composite Triple Endpoint Consisting of Death, Limb Amputation/Gangrene, and New Thrombosis | The mean time to an event is estimated by the area under the survival function. If the largest time is an event time, then the survival function goes to zero at that time, and the mean survival estimate is finite. Otherwise, the mean time cannot be estimated and may lead to a bias. | From the time that the positive heparin PF-4 antibody test was drawn until hospital discharge or day 45, whichever occurred first. | 
| Time to Occurrence of a Composite Triple Endpoint Consisting of Death, Limb Amputation/Gangrene, and New Thrombosis | The median survival time is reported by each group for the time to occurrence of a composite triple endpoint consisting of death, limb amputation/gangrene, and new thrombosis. | From the time that the positive heparin PF-4 antibody test was drawn until hospital discharge or day 45, whichever occurred first. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Time to Death | The mean time to an event is estimated by the area under the survival function. If the largest time is an event time, then the survival function goes to zero at that time, and the mean survival estimate is finite. Otherwise, the mean time cannot be estimated and may lead to a bias. | From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first | 
| Time to Death | The median survival time is reported by each group for the time to death. | From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first | 
| Time to Occurrence of Limb Amputation or Limb Gangrene | Due to the small number of events, the median or mean survival time could not be defined. Therefore, the number of subjects with limb amputation or limb gangrene was reported in Outcome Measure Data Table. | From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first | 
| Time to Occurrence of Radiographically Confirmed Thromboembolism | The mean time to an event is estimated by the area under the survival function. If the largest time is an event time, then the survival function goes to zero at that time, and the mean survival estimate is finite. Otherwise, the mean time cannot be estimated and may lead to a bias. However, the median survival times could not be defined for all three groups, so the mean time was reported in Outcome Measure Data Table. | From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first | 
| Time to Occurrence of Major Bleeding | The mean time to an event is estimated by the area under the survival function. If the largest time is an event time, then the survival function goes to zero at that time, and the mean survival estimate is finite. Otherwise, the mean time cannot be estimated and may lead to a bias. | From the time that the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first | 
| Time to Occurrence of Major Bleeding | The median survival time is reported by each group for the time to occurrence of major bleeding. | From the time that the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first | 
| Proportion of Subjects With HIT With Thrombosis (HIT-T) and Isolated HIT | Proportion of subjects who, at the time the positive heparin PF-4 antibody test was drawn, were in each of the following categories: Group 1: Those with thrombosis and or without thrombocytopenia (HIT-T): 16% of 442 subjects. Group 2: Those with thrombocytopenia but not thrombosis (Isolated HIT): 64% of 442 subjects. Group 3: Those with neither thrombocytopenia nor thrombosis (Neither HIT-T nor Isolated HIT): 20% of 442 subjects. | From the date 5 days before the positive heparin PF-4 antibody test was drawn to the date it was drawn | 
| Type of Heparin Exposure - Unfractionated Heparin (UFH) | Two types of heparins are commonly used as anticoagulants - unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH). UFH has been used for the prevention and treatment of thrombosis for several decades. | Hospital admission to date the positive heparin PF-4 antibody test was drawn, or 28 days prior to the date it was drawn, whichever is later, through the date it was drawn | 
| Type of Heparin Exposure - Low Molecular Weight Heparin (LMWH) | Two types of heparins are commonly used as anticoagulants - unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH). LMWHs are derived from UFH by depolymerization. Each LMWH product has a specific molecular weight distribution that determines its anticoagulant activity and duration of action. | Hospital admission to date the positive heparin PF-4 antibody test was drawn, or 28 days prior to the date it was drawn, whichever is later, through the date it was drawn | 
| Relationship of the Heparin PF-4 (Platelet Factor 4) Antibody Titer to the Clinical Diagnosis | Heparin PF-4 (platelet factor 4) optical density (OD) test results were the dichotomous outcome (<1.0 vs. >=1.0). Clinical diagnosis was three groups (HIT-T, Isolated HIT and No HIT). The Heparin PF-4 optical density test looks for antibodies to complexes of heparin combined with platelet factor 4. Higher optical density indicates higher antibody concentration. We could say that generally OD values above 0.4 are considered a positive result, and that the higher the OD, the greater the concentration of antibodies in the patient's blood. | From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first | 
| Relationship of the Heparin PF-4 Antibody Titer to the Degree of Thrombocytopenia | Heparin PF-4 optical density (OD) test results were the dichotomous outcome (<1.0 vs. >=1.0). Nadir Platelet Count (x10^9 / L) was used for the degree of thrombocytopenia. The Heparin PF-4 optical density test looks for antibodies to complexes of heparin combined with platelet factor 4. Higher optical density indicates higher antibody concentration. We could say that generally OD values above 0.4 are considered a positive result, and that the higher the OD, the greater the concentration of antibodies in the patient's blood. | From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first | 
| Relationship of the Heparin PF-4 Antibody Titer to the Primary Endpoint | Heparin PF-4 OD test results were the dichotomous outcome (<1.0 vs. >=1.0). Primary endpoint was the composite endpoint of death, limb amputation/gangrene, or new thrombosis. | From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first | 
| Use of Treatment (Non-heparin Anticoagulant) Used in Hospital | Types of treatment (direct thrombin inhibitor, fondaparinux, warfarin, no treatment) provided to subjects in hospital | From the time that the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first | 
| Use of Treatment (Non-heparin Anticoagulant) Used at the Time of Discharge |  | From the time that the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first | 
| Time to Platelet Recovery, Among Subjects With a Low Platelet Count When the Positive PF4 Antibody Test Was Drawn |  | From the time that the nadir platelet count was drawn until hospital discharge, death, or day 45, whichever occurred first | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Thrombocytopenia, Heparin