Summary
Heparin-associated thrombocytopenia (HAT) is a severe complication of heparin therapy.
Its diagnosis is difficult. Conventional assays employ platelet aggregometry (PAA)
and/or 14C-serotonin release (SRA) which are either insensitive (PAA) or require radioactive
tracers (SRA). We here describe a newly developed sensitive and rapid assay based
on visual evaluation of heparin-induced platelet activation (HIPA) in microtiter wells.
Using sera of 34 patients with clinically suspected HAT we found the HIPA assay to
be as sensitive as the SRA and superior to PAA. The HIPA assay allows investigation
of crossreactivity with different types of heparins, low molecular weight (LMW) heparins
and heparinoids. Three patients who required further parenteral anticoagulation and
in whom the HIPA assay was negative before treatment with the LMW heparinoid Org 10172,
were treated with this new heparinoid without adverse reactions. We conclude that
the HIPA assay may be a useful tool for differential diagnosis and therapy in patients
with HAT.
