The US Food and Drug Administration (FDA) has issued a warning that certain Roche Diagnostics test strips used with a CoaguChek test meter device to monitor warfarin levels may deliver inaccurate results.

Medical product distributor Terrific Care/Medex Supply voluntarily recalled certain lots of the home-use test strips.

Classifying the recall as Class I, the FDA warned patients and doctors to not rely on results from these test strips to adjust the warfarin dosage. The drug is a blood thinning medication used to address blood clots.

“The recall was attributed to inaccurate INR test results when compared to laboratory results.”

Venous thromboembolism (VTE) is a condition, which results in blood clots forming in veins. Blood clots are life-threatening and must be treated quickly. Anticoagulants medications such as warfarin are often used to prevent blood clots from happening in high-risk patients.

The recalled CoaguChek XS PT Test Strips, manufactured by Roche and distributed by Terrific Care/Medex Supply, were not authorised for sale in the US.

According to the FDA, Terrific Care/Medex Supply purchased the test strips from an unknown source and imported them to the US.

FDA Commissioner Scott Gottlieb said: “Using faulty strips can lead to errors in medication dosage that could cause serious harm or death in some patients. That’s why it’s so concerning that this distributor continued to sell these test strips in the US even though domestic sales had been stopped due to safety concerns.

“Distributing products that are not labelled or authorised for sale in the US raises significant concerns for us in view of the serious safety issues with these test strip devices, and our work on this matter is not finished.”

In November last year, Roche recalled more than 1.1 million packages of CoaguChek XS PT Test Strips distributed between 12 January and 29 October 2018.

The recall was attributed to inaccurate INR test results when compared to laboratory results.

Incorrect INR results, which affect warfarin dosage, could be a concern for patients who are at an increased risk of blood clots, such as people with mechanical heart valves, atrial fibrillation and are at high risk of having a stroke or have had a recent blood clot.

Additional reporting by Charlotte Edwards.