Fehldiagnose HIT bei einem thrombozytopenen Patienten – Fallbeschreibung mit Anmerkungen zur Differenzialdiagnose*

 

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Zusammenfassung

Wir berichten über einen Patienten mit klinischen Zeichen einer medikamenteninduzierten Thrombozytopenie, bei welchem die Diagnose initial durch einen positiven HIT-Antikörpertest fehlgeleitet wurde. Der präsentierte Fall unterstreicht, dass ein positiver Antigentest bei HIT-Verdacht weiter untersucht werden muss, besonders bei niedriger Prä-Test-Wahrscheinlichkeit. Dies ist besonders wichtig, wenn der Antigentest nicht IgG-spezifisch ist. Wir empfehlen die Anwendung des klinischen „4 T-scores“ sowie eine weitere Laboraufbereitung von positiven HIT-Antigentesten mithilfe funktioneller Tests, die einzigen, welche die thrombozytenaktivierende Eigenschaft von HIT-Antikörpern nachweisen können (nicht aktivierende, niedrigtitrige IgG-Antikörper haben wahrscheinlich keine klinische Relevanz).

Abstract

We report on a patient with clinical signs of drug-induced thrombocytopenia in whom the correct diagnosis was delayed by a positive HIT-antibody test. The clinical course demonstrates that a positive antigen test in suspected HIT has to be further examined, especially if pre-test probability is low. This is particularly important if the assay is not IgG-specific. We recommend the use of the “4-T”-score as well as follow-up of positive HIT-antigen tests with functional assays which are the only tests that can demonstrate the platelet activating property of HIT-antibodies (nonactivating, low-titer IgG antibodies are probably clinically irrelevant).

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