Internal Medicine

Answer 4 Diagnosis of HIT is most reliably made when both clinical and pathologic criteria are met. The first step in diagnosing HIT is recognizing the possibility that HIT exists by assessing clinical and laboratory data. While the diagnosis should be confirmed by pathologic testing, the initiation of treatment should begin prior to obtaining test results. Most tests available for detecting HIT are time-consuming. Many of the tests are not available at all medical centers, adding to the length of time needed for pathologic diagnosis. The 14C-serotonin release assay is considered the “gold standard” in HIT testing due to its high specificity and sensitivity. Disadvantages of the test include high technical demand, use of radioactivity, and high cost. The concordance between the two types of testing for HIT (ie, activation assays, enzyme immunoassays) is only approximately 80% to 90%, making “cross-verification” necessary (ie, confirmation of a borderline result with one test by using a second test). Click here to return to the questions

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