Instrumentation Laboratories, part of Werfen, is removing four lots of its HemosIL AcuStar HIT-IgG(PF4-H) assay after confirming the test reports results 20 to 35 percent below true values. FDA posted the notice on October 30 and describes it as the most serious type of recall.
The assay detects IgG antibodies against platelet factor 4 complexed with heparin. Clinicians use it to assess whether a patient has heparin-induced thrombocytopenia. A negative bias pushes samples under the 1.00 U/mL cutoff, so a patient carrying HIT antibodies can read negative. One customer saw a 47 percent negative mean bias on patient samples. Another reported an invalid calibration curve.
Routine calibration and quality control may not reliably detect the shift, according to the notice. Affected lots are B40005 and B38062 of part 0009800127, and B40006 and B38063 of part 0009802028. Werfen told customers to destroy remaining product, document it on an Urgent Mandatory Response Tracking Form, and line up an alternative HIT antibody method, because it expects a supply interruption. As of September 3 the company had reported no serious injuries or deaths.
A failure mode that passes the manufacturer's own controls is the one to read twice. Labs running only those controls had no signal here, and the root cause investigation is still open.