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

Study Status: Completed
Recruit Status: Completed
Study Type: Observational

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

Brief Summary: 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 Summary:

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.

Current Primary Outcome:

• Time to Occurrence of a Composite Triple Endpoint Consisting of Death, Limb Amputation/Gangrene, and New Thrombosis [ Time Frame: From the time that the positive heparin PF-4 antibody test was drawn until hospital discharge or day 45, whichever occurred first. ]
  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.
• Time to Occurrence of a Composite Triple Endpoint Consisting of Death, Limb Amputation/Gangrene, and New Thrombosis [ Time Frame: From the time that the positive heparin PF-4 antibody test was drawn until hospital discharge or day 45, whichever occurred first. ]
  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.

Original Primary Outcome: Time to Occurrence of a Composite Triple Endpoint Consisting of Death, Limb Amputation/Gangrene, and New Thrombosis [ Time Frame: From the time that the positive heparin PF-4 antibody test was drawn until hospital discharge or day 45, whichever occurred first. ]

Current Secondary Outcome:

• Time to Death [ Time Frame: From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first ]
  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.
• Time to Death [ Time Frame: From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first ]
  The median survival time is reported by each group for the time to death.
• Time to Occurrence of Limb Amputation or Limb Gangrene [ Time Frame: From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first ]
  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".
• Time to Occurrence of Radiographically Confirmed Thromboembolism [ Time Frame: From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first ]
  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".
• Time to Occurrence of Major Bleeding [ Time Frame: From the time that the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first ]
  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.
• Time to Occurrence of Major Bleeding [ Time Frame: From the time that the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first ]
  The median survival time is reported by each group for the time to occurrence of major bleeding.
• Proportion of Subjects With HIT With Thrombosis (HIT-T) and Isolated HIT [ Time Frame: From the date 5 days before the positive heparin PF-4 antibody test was drawn to the date it was drawn ]

  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.
• Type of Heparin Exposure - Unfractionated Heparin (UFH) [ Time Frame: 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 ]
  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.
• Type of Heparin Exposure - Low Molecular Weight Heparin (LMWH) [ Time Frame: 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 ]
  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.
• Relationship of the Heparin PF-4 (Platelet Factor 4) Antibody Titer to the Clinical Diagnosis [ Time Frame: From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first ]
  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 opt
  
  

  Original Secondary Outcome:

  • Time to occurrence of radiographically confirmed thromboembolism [ Time Frame: 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 [ Time Frame: 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 [ Time Frame: From the time 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 [ Time Frame: From the date 5 days before the positive heparin PF-4 antibody test was drawn to the date it was drawn ]

    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 both thrombosis and thrombocytopenia (HIT-T)
    • Group 2: Those with thrombosis but not thrombocytopenia (HIT-T)
    • Group 3: Those with thrombocytopenia but not thrombosis (Isolated HIT)
    • Group 4: Those with neither thrombocytopenia nor thrombosis (Neither HIT-T nor Isolated HIT)
  • Type of heparin exposure [ Time Frame: 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 antibody titer to the clinical diagnosis, degree of thrombocytopenia, and the primary endpoint [ Time Frame: From the time the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first ]
  • Type of treatment provided to subjects in hospital and at the time of discharge [ Time Frame: From the time that the positive heparin PF-4 antibody test was drawn until hospital discharge, death, or day 45, whichever occurred first ]
    Types of treatment (direct thrombin inhibitor, fondaparinux, warfarin, no treatment) provided to subjects in hospital and at the time of discharge
  • Time to Platelet Recovery, Among Subjects With a Low Platelet Count When the Positive PF4 Antibody Test Was Drawn [ Time Frame: 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 [ Time Frame: 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. A major bleeding event is defined as any 24 hour period in which 2 or more units of RBC are transfused OR radiographically confirmed intracranial hemorrhage.

  
  
  Information By: New England Research Institutes
  

  Dates:
  Date Received: August 6, 2010
  Date Started: June 2010
  Date Completion:
  Last Updated: May 6, 2015
  Last Verified: March 2013
  

  

  Join Millions

  Sign Up For One Of Our
  Newsletters

  Email

  Sign Up