Alere Inc., a point-of-care diagnostics and services provider, has voluntarily recalled a series of its blood clot test strips after nine reports of severe adverse events, including three patients bleeding to death. The root cause for the problem is still unknown, and Alere plans to explore what factors may have affected the test strips’ false outcomes.

The test strip PN 99008G2 monitors the blood of patients on the anticoagulant warafin by measuring how long it takes for their blood to clot, Reuters reported. In this certain series of strips there were significant differences in test results between the Alere Professional Test Strips and the local laboratory plasma INR test, according to The Wall Street Journal. Results from the Alere strips were between 3.1 and 12.2 INR units lower than the official laboratory results. Customers were asked to immediately stop using the products after the company received several reports of adverse events occurring because of the false readings. Alere has reported the complaint to the Food and Drug Administration.

At the moment, the details surrounding the adverse effects are still unclear. “The root cause for this issue has not yet been determined; therefore Alere cannot determine the patients’ conditions or circumstances that may contribute to the discrepancy,” the company said. They are currently conducting an investigation into the causes for this tragic event. In place of the Alere testing strips, customers are advised to use an alternate Alere product or point-of-care monitoring system. Unused products should be returned to the company.

Patients prescribed anticoagulants, or blood thinners, such as warafin, are able to have thier PT/INR levels tested by health professionals using the Alere Professional Test Strips.These tests are used to determine the blotting tendency of blood.

Within seconds of cutting a blood vessel, the damaged tissue causes tiny cells in the blood to become sticky and clump together around the cut. If a blood clot forms within a blood vessel, it can cause serious problems. Anticoagulants work by interfering with the chemicals needed to make clots. By blocking vitamin K, the blood clots are prevented from forming so easily. When a patient is on blood thinners, they need to take regular blood tests to check how quickly their blood clots. A wrong reading may be a sign that the individual is taking the wrong dosage of anticoagulant. This would cause them to bleed or bruise easily. Also once bleeding starts, the blood may not be able to stop as quickly as normal.