Why did you (and your colleagues) write this paper? What was its main purpose?

ULRICH SACHS AND KARINA ALTHAUS

The pathophysiology of heparin-induced thrombocytopenia (HIT) and vaccine-induced thrombotic thrombocytopenia (VITT) share many similarities. It became clear very early that functional tests which work for HIT can be used for VITT when modified slightly. However, they are only available in specialized laboratories and their turn around-time is long. Accordingly, fast, commercially available, ready-to-go assays should be used as a first step in a diagnostic algorithm for VITT. Since the different HIT screening assays on the market have a different chemistry, especially with regard to the main test components (which are platelet factor 4 and a polyanion such as, heparin), and since we know from previous studies performed by us and others that inter-assay comparability for HIT can be affected by test composition, we aimed to compare the most often used commercial tests to guide diagnostic laboratories.

What are the main conclusions? 

ULRICH SACHS AND KARINA ALTHAUS

So called "rapid" tests for HIT diagnosis such as, the gel-card based PaGIA, the lateral flow immunoassay and the fully automated chemiluminescence assay cannot be used to diagnose VITT patients, since their sensitivity is below 25%. I. E. most VITT patients are missed if these tests are used. 

What are the paper's implications? - to the public? -to medical professionals?

ULRICH SACHS AND KARINA ALTHAUS

The message for medical professionals is that the "rapid" tests have to be avoided. This also implies for physicians in contact with these patients that they will have to tell the laboratory whether a patient sample is send for suspicion of VITT (rapid assays useless) or HIT (rapid assays useful). It is also relevant to the public because ELISA can be used as an initial screening test and, together with increasing d-dimer and decreasing platelet counts, as an potential positive predictor for VITT. In such an algorithm, appropriate patient care can be delivered before the functional test result is reported back from the specialized lab.

Are the findings clinically significant? Should the findings change practice?

ULRICH SACHS AND KARINA ALTHAUS

Misdiagnosis of VITT can be avoided if the appropriate screening test is used. Local laboratories should establish a policy to ensure that the suspected diagnosis accompanies a patient sample and that the correct test is used, either locally or in a reference laboratory.