Background HIT is a prothrombotic adverse drug reaction caused by heparin and requires an alternative anticoagulant: danaparoid. Because of its cost and the specific indication, the physicians must request two laboratory tests with prescriptions (LT: Platelet Aggregation Test, Anti PF4H) and a 4Ts assessment, in order to have danaparoid dispensed.

Purpose To find out whether prescriptions are justified and if we can use the 4Ts score as a basis for HIT detection.

Materials and Methods We analysed 5 years of prescriptions: 4Ts score results (the 4Ts assessment is used to arrive at a high (score 6 or more), intermediate (score 4–5) or low (score 3 or less) probability of HIT.

Of 72 hospitalised patients followed (LT and/or prescription), 34 had a LT score without danaparoid prescription (32 negative and 2 positive results). 38 had a prescription that had been dispensed. 32 patients of these 38 had a 4Ts score. Looking at the 4 Ts’ results:

• 3.12% (1/32) patients had low score (LT not requested).

• 62.5% (20/32) came into the intermediate category (LT: 8/20 negative – 4/20 positive – uncertain 3/20 – not requested 5/20).

• 34.4% (11/32) came into the high-score group (LT: 4/11 negative – 4/11 positive – 1/11 uncertain – not requested 2/11).

In 60.5% of the cases (23/38), the prescription was justified by a high score or a positive LT test or HIT diagnosed before. In 39.5% of the cases (15/38), a danaparoid prescription wasn’t justified: 7 patients still received danaparoid after negative LT results and 8 without a 4Ts score.

Conclusions In our hospital, positive predictive value doesn’t match like it’s written in the literature. The 4Ts score doesn’t seem to favourably correspond with HIT laboratory testing results. A new scoring HIT Expert Probability Score is right now in validation. Will it be more suitable for our practise?

No conflict of interest.