Prospective evaluation of the ‘4Ts’ score and particle gel immunoassay specific to heparin/PF4 for the diagnosis of heparin‐induced thrombocytopenia

Abstract

To cite this article: Pouplard C, Gueret P, Fouassier M, Ternisien C, Trossaert M, Ré gina S, Gruel Y. Prospective evaluation of the Ô4TsÕ score and particle gel immunoassay specific to heparin/PF4 for the diagnosis of heparin-induced thrombocytopenia. J Thromb Haemost 2007; 5: 1373-9.See also Arnold DM, Kelton JG. Testing for heparin-induced thrombocytopenia: are we there yet? This issue, pp 1371-2.Summary. Background: Heparin-induced thrombocytopenia (HIT) is a severe disease that is often difficult to diagnose. A clinical scoring system, the Ô4TsÕ score, has been proposed to estimate its probability before laboratory testing, and a particle gel immunoassay (H/PF4 PaGIA Ò ) has also been developed for rapid detection of HIT antibodies. Aim: To evaluate the performance of both methods when HIT is suspected clinically. Methods: Two hundred thirteen consecutive patients were included in four centers. The probability of HIT was evaluated using the 4Ts score blind to antibody test results. HIT was confirmed only when the serotonin release assay (SRA) was positive. Results: The risk of HIT was evaluated by the 4Ts score as low (LowR), intermediate (IR) or high (HR) in 34.7%, 60.6% and 4.7% of patients, respectively. The negative predictive value (NPV) of the 4Ts score was 100%, as the SRA was negative in all LowR patients. PaGIA Ò was negative in 176 patients without HIT (99.4%, NPV) and the negative likelihood ratio (LR-) was 0.05. PaGIA Ò was positive in 37 patients, including 21 with HIT (positive predictive value = 56.8%), with a positive LR of 11.4. A negative PaGIA Ò result decreased the probability of HIT in IR patients from 10.9% before assay to 0.6%, whereas a positive result did not substantially increase the likelihood for HIT. Conclusion: The use of the 4Ts score with PaGIA Ò appears to be a reliable strategy to rule out HIT.

Relationship between the 4Ts scoring system and the antiplatelet factor 4/heparin antibodies test in critically ill patients

“…30 The positive predictive value of the 4Ts score was as low as 15.4%, a value less than the previously reported range from 21.4% to 100%. [8][9][10]15,[22][23][24][25][26] The false-positive rate of the 4Ts score (percentage of "4T high score" patients in the non-HIT patients) was 11.8%, a value comparable to those previously reported (0-15.3%). [8][9][10]15,[22][23][24][25][26] In contrast, the false-negative rate of the 4Ts scores (percentage of "4T low score" patients in HIT patients) was 54.5% (6/11), a value considerably higher than those previously reported (0-25%).…”

“…[8][9][10]15,[22][23][24][25][26] The false-positive rate of the 4Ts score (percentage of "4T high score" patients in the non-HIT patients) was 11.8%, a value comparable to those previously reported (0-15.3%). [8][9][10]15,[22][23][24][25][26] In contrast, the false-negative rate of the 4Ts scores (percentage of "4T low score" patients in HIT patients) was 54.5% (6/11), a value considerably higher than those previously reported (0-25%). [8][9][10]15,[22][23][24][25][26] These findings suggested that many individuals might develop HIT even with a low 4Ts score.…”

“…9 High negative predictive values ranging from 91.4% to 100% have been reported in subsequent studies carried out in medical-surgical ICU patients and cardiothoracic surgical patients. [8][9][10]15,[22][23][24][25][26] In the present study, a high negative predictive value of 4Ts score, 87.5%, was obtained for HIT, similarly to the previous studies mentioned above. This value was still lower than the values ranging from 91.4% to 100% in previous reports.…”

“…[8][9][10]15,[22][23][24][25][26] In contrast, the false-negative rate of the 4Ts scores (percentage of "4T low score" patients in HIT patients) was 54.5% (6/11), a value considerably higher than those previously reported (0-25%). [8][9][10]15,[22][23][24][25][26] These findings suggested that many individuals might develop HIT even with a low 4Ts score.…”

Experts’ opinion or the serotonin release assay as a gold standard for the diagnosis of heparin‐induced thrombocytopenia (HIT)?

“…Five studies evaluating a clinical score (4 Ts) [6][7][8][9][10] and three studies evaluating an IA were included [6,8,10]. In all of these studies but one [9], HIT was diagnosed if serotonin release was > 20% with 0.1 U mL )1 heparin and < 20%…”