Messmore et al developed a simple scoring system for early recognition and management of heparin-induced thrombocytopenia. The authors are from Hines Veterans Administration Hospital and Loyola University in Chicago.


A patient receiving heparin was given a score of 0 or 1.


Criteria for score of 1 - all of the following:

(1) The patient is on heparin therapy (currently or within 5 days of onset).

(2) The patient has had either a drop in the platelet count > 30% OR a new thrombosis.

(3) There is no significant competing cause for the findings.


Laboratory tests used to confirm HIT:

(1) heparin-induced platelet aggregation (sensitivity 19%, specificity 89%)

(2) serotonin release assay (sensitivity 11%, specificity 98%)

(3) ELISA for HIT antibody (sensitivity 27%, specificity 87%)


If the patient is given a score of 1 then:

(1) discontinue heparin therapy pending test results

(2) give an alternative non-heparin anticoagulant if clinically indicated


A patient who does not have a score of 1 (i.e., score 0) may continue heparin therapy if clinically indicated pending test results. The patient should be reassessed if one of the laboratory tests becomes positive or the patient develops other findings of HIT.



• This is more of a rule than a scoring algorithm.


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