The Food and Drug Administration recently upgraded the recall of Alere INRatio and INRatio2 Monitor Systems to a Class I recall, meaning that there is a reasonable probability that using the Alere systems will cause serious or adverse health consequences or possibly lead to death.

The original recall, which was announced last year, regarded the Alere INRatio and INRatio2 monitor system providing falsely low international normalized ratio (INR) levels in patients on blood thinners, such as warfarin.

Patients use Alere’s monitor systems and test strips to measure how quickly their blood clots, specifically their Prothrombin Time (PT). Because warfarin and other blood thinners block vitamin K, the medicines prevent clots from easily forming. Depending upon the results of the INR/PT test, patients could be taking the wrong dosage of anticoagulants and be at a higher risk for major blood loss or possibly even death.

The recall comes after Alere received nearly 19,000 reports of device malfunctions, including 14 which resulted in serious injury. A press release from Alere acknowledged that the false levels resulting from the use of their PT/INR test strips had resulted in the company receiving “serious adverse event reports,” some of which “described bleeding associated with patient deaths.”

“For the company to allow literally tens of thousands of reports of malfunctions before taking action is grossly negligent if not criminal,” said Ned McWilliams, Alere INRatio lawyer for the Levin, Papantonio Law Firm. “The absolutely critical importance of this device to provide accurate results cannot be overstated.”

According to the FDA, “use of the affected devices may delay treatment and cause severe or life-threatening injuries, including death,” and that patients suffering from certain medical conditions, including but not limited to anemia, acute or chronic inflammatory conditions, severe infections, and advanced stage cancer or end stage renal disease, should not use the Alere INRatio and INRatio 2 Monitoring systems and test strips.

Patients affected by these conditions were instead instructed to stop using the Alere INRatio and InRatio2 Monitoring Systems and test strips, and “should immediately be transitioned to a laboratory INR method for monitoring for their INR and warfarin therapy,” said FDA documents.

The recall affects Alere INRatio and INRatio2 Monitor Systems manufactured and distributed between April 2008 and December 2014.