The FDA has classified the recall of four affected lots as the most serious type after performance issues were identified that routine quality control may not detect.

Instrumentation Laboratories (Werfen) is removing select lots of its HemosIL AcuStar HIT-IgG(PF4-H) assay over concerns about false-negative results. The US Food and Drug Administration (FDA) has classified the recall as the most serious type, warning that continued use may cause serious injury or death.

The manufacturer initiated the removal after customer complaints identified invalid calibration curves and performance issues, including one report of a negative mean bias of 47% with patient samples. Subsequent investigations confirmed performance variability showing a negative bias of 20% to 35% across the affected lots.

The company found that this bias may not be reliably detected through routine calibration and quality control procedures. The root cause investigation remains ongoing.

Clinical Risks of Underreported Titers

The HemosIL AcuStar HIT-IgG(PF4-H) assay is a qualitative, fully automated, chemiluminescent immunoassay used to detect IgG antibodies that react with Platelet Factor 4 (PF4) complexed to heparin. The qualitative positive or negative results aid clinicians in assessing the risk of heparin-induced thrombocytopenia (HIT) alongside other laboratory and clinical parameters.

Because of the assay’s performance variability, negative bias can cause patient sample results to fall below the diagnostic cut-off of 1.00 U/mL, resulting in an incorrect report of “HIT IgG Antibody negative.” A false-negative finding may delay the clinical recognition of HIT, leading clinicians to continue heparin therapy. In patients with HIT, uninterrupted exposure to heparin significantly increases the risk of severe thrombotic complications.

As of September 3, no serious injuries or deaths associated with the recalled lots have been reported.

The recall impacts four specific production lots spanning two catalog part numbers:

  • Part No. 0009800127 (UDI 08426951126545): Lot B40005 (expiration date 2027-01-16) and Lot B38062 (expiration date 2026-11-01)
  • Part No. 0009802028 (UDI 08426950545774): Lot B40006 (expiration date 2027-01-16) and Lot B38063 (expiration date 2026-11-01)

Laboratories are instructed to inspect inventory and destroy all remaining units from the affected lots in accordance with facility standard procedures. Facilities must document the quantity destroyed and the destruction date on an Urgent Mandatory Response Tracking Form.

Because a supply interruption is expected, the manufacturer advises laboratory teams to identify an alternative method for HIT antibody testing and collaborate with local Werfen representatives for transition guidance.

The FDA notes that decisions regarding previously reported patient results, repeat testing, or patient follow-up must be determined by the laboratory, treating clinicians, and the laboratory medical director in alignment with institutional protocols and regulatory requirements. Adverse reactions or product quality issues may be submitted to the FDA MedWatch program.

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