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Using the HIT Calculator

Data entry for the calculator is done in the checkboxes to the left. All are easily obtained historical or clinical parameters. One box should be selected for each group of radio buttons - Heparin Type, Patient Characteristics, Thrombocytopenia, Thrombosis, Timing and oTher. If all questions have not been considered, some of the risk scores will be incorrect, therefore you will be prompted for a response if data is missing. Data choices can be changed at any time, or you can start over. Once data input is complete, this will be indicated alongside the 4T's score.

The calculator result will grade the risk of HIT with or without thrombosis as a 4T's score, and rate this as low, intermediate or high. It will also apply current algorithms to determine whether platelet monitoring should be done by considering heparin type and patient characteristics. Finally, a recommendation is made as to whether heparin should be replaced by an alternate anticoagulant, and whether HIT antibody testing should be done. The specifics of use of direct thrombin or factor Xa inhibitors are not addressed.

This tool was developed for to support decision making regarding platelet counts and clinical findings in patients treated with heparin. Use is appropriate in all situations where heparin is used because, if there is uncertainty about platelet monitoring, or if thrombosis develops, an estimate of pretest probability will guide further testing and therapy. The rationale and references underlying recommendations contained in this application can be found here.

To find other medical calculators and reference material, go to the PalMed Website.

Downloading this calculator for use on your own desktop

This application will run from the internet, but will be more accessable if transferred to your own computer. 1. It is suggested that you unzip these files to a newly created folder. All the files must be in the same folder otherwise hyperlinks will not function.

2. Run the application from the file titled HIT.html. Documentation and help can be accessed from the calculator.

3. Create an icon for your desktop if you wish by right-clicking on coagcalc.html and select Send to > Desktop (create shortcut). In Windows 7, right click and select Create Shortcut. The new shortcut created in your folder can be dragged to the desktop. Double clicking on this icon will then open the calculator application. You can rename the shortcut or change the icon if you wish with another right click on the new desktop icon.

4. This is a javascript based application, so javascript must be enabled in your browser. So far it is tested in Firefox, Safari, Google Chrome and Internet Explorer. This tool will only function on mobile devices if javascript is supported, and the format can be confusing on a small screen.

To download the zipped files after creating the folder for them, click here. This application will run from the internet, but will be more accessable if transferred to your own computer.


This application is offered as is for unlimited use in a clinical setting. Although considerable fact checking and beta testing have been done, the author does not guarantee that it is free of inaccuracies. The user must bear the responsibility for assuring that the results are accurate and reliable. If problems are encountered with setup or operation of this tool, please contact the author.

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