Class I recall hits a hospital test for a dangerous clotting reaction

The Food and Drug Administration has classified as Class I — its most serious recall tier, reserved for defects that could cause serious injury or death — a recall of a laboratory test used to diagnose a dangerous reaction to the blood thinner heparin. The agency logged the action in its enforcement database on 21 October 2026 [s1].

The product is the HemosIL AcuStar HIT-IgG(PF4) assay, made by Instrumentation Laboratory. The recall covers two catalogue versions: part number 0009800127, with 434 units affected, and part number 0009802028, with 1,414 units [s1][s2]. The company began the recall on 3 September 2026, and the FDA lists both actions as ongoing [s1][s2].

What the test is for

The assay detects heparin-induced thrombocytopenia, or HIT — one of the more dangerous paradoxes in medicine. Heparin is given to prevent and treat blood clots, but in a minority of patients the immune system reacts to it by making antibodies against a complex of heparin and a blood protein called platelet factor 4 (PF4). Those antibodies activate platelets, which both drops the platelet count and, counter-intuitively, drives the formation of new clots. Untreated, HIT can cause limb-threatening or life-threatening thrombosis.

The AcuStar test looks for those anti-PF4/heparin antibodies. Its most important job is often to help rule the condition out quickly, so clinicians know whether they can keep using heparin or must switch a patient to an alternative anticoagulant. The decision turns on getting the result right.

The defect

The recall notice states the problem directly: the affected lots carry a "potential for invalid calibration curve or negative mean bias of up to 47% with patient samples" [s1]. A negative bias means the test can report a result lower than the true value. For an assay whose purpose is to flag the presence of dangerous antibodies, a reading pushed down by nearly half risks turning a positive sample into an apparently negative one — a missed or underestimated diagnosis [s1][s2].

The clinical stakes follow from that. If a HIT result reads falsely low, a patient who should be taken off heparin might be left on it, allowing the antibody-driven clotting to continue. The specific lots named are B40005 and B38062 for the first part number, and B40006 and B38063 for the second, with expiry dates in late 2026 and early 2027 [s1][s2].

The reach

Distribution is wide. The records list US nationwide shipment across sixteen states — including Arizona, California, Florida, Georgia, Massachusetts, New York and Pennsylvania — and export to more than twenty countries across Europe, Asia and the Middle East [s1][s2]. One of the two part numbers is marked for use outside the United States, but both appear in the same multinational distribution pattern [s2]. This is a hospital and reference-laboratory product, not something a patient would handle; the recall is directed at the labs that run the assay [s1].

What it means

A Class I recall of a diagnostic is different from a recall of a drug or an implant. The hazard is not the device harming the body directly, but the device giving an answer a clinician then acts on. When that answer can be wrong by up to 47% in the low direction, the risk is a decision made on bad information — in this case, potentially leaving a patient exposed to a drug their body is reacting against [s1].

For the laboratories involved, a Class I recall sets a clear task: identify whether any of the named lots are in use, stop using them, and follow Instrumentation Laboratory's instructions for replacement or alternative testing. Clinicians who have relied on recent HIT results from the affected lots may need to confirm them by another method. The enforcement records describe the potential for erroneous results; they do not report any count of patients harmed [s1][s2].

Red flags belong with a care team, not a lab bench: in anyone receiving heparin, a falling platelet count, new or worsening clots, or swelling and pain in a limb are warning signs of HIT that call for urgent assessment. This article describes two FDA enforcement actions and is not medical advice. Questions about a recent HIT test or heparin treatment are for the treating clinicians, who can judge whether affected lots were involved and whether a result needs rechecking.