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        In Vitro Diagnostics

Warfarin INR Test Meters

                        
                Tips for Patients and Caregivers Using INR Test Meters at Home
          Information for Health Care Providers Using INR Test Meters in a Clinical Setting Home
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          Warfarin INR Test MetersIn Vitro Diagnostics Warfarin INR Test Meters
  	
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    PrintAn INR test meter is a portable, battery-operated meter, used to monitor patient response to warfarin. The meter has a screen that displays results, and an opening for meter-specific test strips. A test strip is inserted into the meter, and then a lancet (a medical pricking needle) is used to obtain blood which is applied to the test strip. The meter reads the test strip, measures how long it takes the blood to clot, and provides the result based on a standardized calculation in the form of the International Normalized Ratio, or INR. The INR is used by patients and physicians to determine if warfarin dosing is appropriate.

INR test meters and test strips are medical devices regulated by the U.S. Food and Drug Administration. The FDA wants to ensure patients and health care providers use these devices safely. Please read on for more information.

What is Warfarin?

Warfarin (also known by the brand names Coumadin and Jantoven) is a blood thinner prescribed to prevent and treat blood clots. Warfarin therapy may be prescribed for patients with certain types of irregular heartbeat, blood clots in the legs or lungs, and patients who have certain medical device implants such as artificial heart valves.

A patient’s warfarin dose depends on many factors, including the patient’s age, overall health and genetic makeup. The dose may also need to be adjusted based on a patient’s diet and current medications.

Monitoring Warfarin

Warfarin must be monitored to ensure it is working effectively and being used safely. Achieving the correct warfarin dosage can be difficult but is extremely important. If the dose of warfarin is too low, the patient is at risk of developing harmful blood clots. If the dose of warfarin is too high, the patient may be at risk of serious bleeding. It can be monitored by drawing blood from a vein and sending the blood to an accredited laboratory to test, or it can be monitored by testing blood from a fingerstick with an INR test meter outside of a laboratory. INR test meters may be prescribed to patients for use in the home, and they may also be used by health care providers at the point of care, such as a health care setting.

How often an INR test meter is used to monitor warfarin, and the results a patient should expect, will be based on recommendations from the patient’s health care provider. An INR target range is set by a health care provider. It is typically between 2.0 and 3.0 for basic blood-thinning needs, though the range may vary based on a patient’s specific conditions. An INR above the patient-specific target range may increase the risk of bleeding, while an INR below the target range may increase the risk of developing a blood clot.
Patients should work with their health care provider to develop a plan for achieving and maintaining a target INR; recognize when there is a problem; and know when to contact their health care provider.

The information and resources on this website are intended to provide useful information for patients and caregivers who are using INR test meters in the home and for health care providers using INR test meters in a clinical setting.

**Home Users - Patients and Caregivers:** For more information and tips on using an INR test meter to monitor warfarin safely and effectively, visit Tips for Patients and Caregivers Using INR Test Meters at Home.

**Health Care Providers:**For more information and tips on using an INR test meter to monitor warfarin safely and effectively, visit Tips for Health care Providers Using INR Test Meters in a Clinical Setting.

How to Report a Problem

All health care providers, patients and caregivers, are strongly encouraged to voluntarily report INR test meter problems directly to the FDA through MedWatch, the FDA’s voluntary reporting program. Problems should be reported whenever one suspects there is an issue with an INR test meter such as a malfunction or incorrect result, or that the meter caused or contributed to a serious injury or death. Hospitals, nursing homes, coagulation clinics, and outpatient facilities should follow the reporting procedures established by their facilities. INR test meter users should also report these problems to the manufacturer using the phone number listed on your meter’s instructions.

When submitting a report through MedWatch, please include as much of the following information as possible:

Brand of the test meter involved (and the model or catalog number, if known)
	Lot number of the test strips involved
	Date of the event
	Whether you are the patient, a family member or a health care provider
	Whether the manufacturer was notified about the problem
	Patient's age
	Description of patient’s symptoms before and after the incorrect test result
	Detailed description of the event, such as:
	The initial INR test meter result
		Whether the blood sample was collected according to the manufacturer’s recommendations
		If the test was repeated by the laboratory and you are reporting an incorrect result, include:
		The laboratory test result
			The time period between the repeated testing (e.g., 10 minutes later, or several hours later)
			What conditions changed between the two INR tests (for example, using a different finger, using a lab test or different INR test meter, taking medication or eating leafy greens between INR tests)
			Test results prior to the incorrect test resultWhat types of problems should be reported?

The following are examples of some of the problems that may arise and should be reported:

Test strip or test meter defects
	Quality control problems (liquid control solutions, test strip controls)
	INR test meter fails to perform as described in the labeling
	Discrepant test results (such as falsely low INR results as compared to a lab test) that caused or contributed to an incorrect warfarin or vitamin K dosage
	Difficulty understanding the INR test meter or test strip instructions
	Difficulty using the meter
	INR test meter stops working unexpectedly
	Unexplained bleeding, any other problems that compromise patient health or safety, or death**Related Resources:﻿**

The FDA Warns Against Use of Previously Owned Test Strips or Test Strips Not Authorized for Sale in the United States: FDA Safety Communication
	Public Workshop - Point-of-care Prothrombin Time/International Normalized Ratio Devices for Monitoring Warfarin Therapy
	Transcript of FDA Press Conference on Warfarin

                                                                                  Content current as of:
      06/21/2022
                  
                   
Regulated Product(s)
		 Medical DevicesWarfarin INR Test Meters                
                          

                        Tips for Patients and Caregivers Using INR Test Meters at Home
          Information for Health Care Providers Using INR Test Meters in a Clinical Setting
 
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