CDC Asks for Review After Blood Error

PHILADELPHIA —  The U.S. Centers for Disease Control and Prevention asked hospitals nationwide Friday to review their laboratory procedures after a deadly error at a Philadelphia hospital.

St. Agnes Medical Center incorrectly interpreted a test used to measure blood clotting, leading dozens of patients to receive overdoses of a blood thinner. Two people died as a result, the city medical examiner ruled.

The lab error involved the prothrombin time (PT) test, which measures blood thickness. Physicians routinely use the test and the International Normalized Ratio to monitor the effect of warfarin--a widely prescribed anticoagulant better known by the brand name Coumadin--on the blood. The INR is a numeric value used to standardize PT results.

Employees at a St. Agnes lab failed to verify the sensitivity of a chemical reagent used in the PT test, leading them to use the wrong INR to calculate the result. The error led some physicians to prescribe a stronger dose of warfarin.

The CDC’s Morbidity and Mortality Weekly Report said labs should review the reagent package insert information to verify that the correct INR is being used. The agency also recommended that labs give doctors both the PT number and the adjusted INR number.