Class 1 Recall for HemosIL AcuStar HIT Antibody Test

The U.S. Food and Drug Administration (FDA) has identified a recall of certain lots of the HemosIL AcuStar HIT-IgG(PF4-H) diagnostic test, manufactured by Instrumentation Laboratories (Werfen), as the most serious type of medical device recall.

The recall involves a performance problem that could cause the test to incorrectly report negative results in patients being evaluated for heparin-induced thrombocytopenia (HIT), a potentially life-threatening reaction to the blood-thinning medication heparin.

Why the Recall Matters

Heparin is commonly used in hospitals to prevent or treat blood clots. In some patients, however, it can trigger an immune reaction that reduces platelet counts and increases the risk of dangerous blood clots.

The HemosIL AcuStar HIT-IgG(PF4-H) test helps clinicians evaluate patients for this condition by detecting antibodies associated with HIT.

According to the FDA, customer complaints identified problems with test calibration and inaccurate results. Werfen subsequently confirmed that certain lots could produce results with a negative bias of 20% to 35%, meaning the test could report antibody levels lower than their actual values.

More concerning, the problem may not be reliably detected through routine calibration and quality control testing.

As a result, some patient samples could be incorrectly reported below the test’s cutoff of 1.00 U/mL and interpreted as negative for HIT antibodies.

A false-negative result could delay recognition of HIT and influence treatment decisions. Continued heparin exposure in a patient with HIT could increase the risk of serious thrombotic complications.

Products Affected

The recall affects four lots of HemosIL AcuStar HIT-IgG(PF4-H):

Actions for Healthcare Facilities

Werfen has instructed affected customers to identify and destroy remaining products from the recalled lots, document the destruction, and arrange alternative HIT antibody testing methods. The company has also warned that a supply interruption is expected. Werfen’s investigation into the root cause remains ongoing.

Laboratories and treating clinicians should determine whether previously reported patient results require review, follow-up, or repeat testing based on clinical judgment and applicable procedures.

As of September 3, 2026, the company had reported no serious injuries or deaths associated with the issue.

Regulatory Intelligence Perspective

This recall illustrates an important challenge involving diagnostic devices, that a test can produce an apparently valid result even when its analytical performance is compromised. The reported negative bias is particularly concerning because routine calibration and quality control procedures may not reliably identify the problem.

For diagnostic manufacturers and clinical laboratories, the recall underscores the importance of investigating performance complaints, evaluating potential effects on previously reported patient results, and assessing whether existing quality controls are capable of detecting clinically significant failures.

The case also demonstrates why postmarket surveillance and effective corrective action processes are essential throughout a diagnostic device’s commercial life.

Additional information

U.S. customers may contact Werfen Client Services at 1-800-955-9525. FDA recall information is available through the agency’s Medical Device Recalls and Early Alerts website.