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

Abstract

Aim: Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction and potentially progresses to fatal thrombosis. The 4Ts scoring system has been reported as a clinical pretest for HIT. However, its usefulness in critically ill patients has not yet been thoroughly examined. Thus, we evaluated the clinical usefulness of the 4Ts score in the diagnosis of HIT in critically ill patients. Methods:One hundred and four critically ill patients who were admitted to our intensive care unit and who underwent the antiplatelet factor 4/heparin complex antibodies (PF4/heparin Ab) test with suspected HIT were enrolled in the study. The primary endpoint variable was the 4Ts score. The secondary endpoint variables were laboratory data, length of stay, and mortality, compared between thePF4/ heparin Ab positive and negative groups.Results: There was no significant difference in the 4Ts scores between the PF4/heparin Ab positive and negative groups. The positive predictive value (HIT patients/4T high score patients) was 15.4% (2/13), the negative predictive value (non-HIT patients/4T low score patients) was 87.5% (42/48), and the false-negative rate for the 4Ts score (4T low score patients/HIT patients) was as high as 54.5% (6/11). The PF4/heparin Ab positive patients had longer stay in intensive care compared to the PF4/heparin Ab negative patients (P = 0.035). Conclusions:The present study showed the discrepancy between the 4Ts score and PF4/heparin Ab. When HIT is suspected in critically ill patients, an immediate HIT antibody test and initiation of therapeutic management of HIT are required regardless of the 4Ts score.

Three cases of heparin‐induced thrombocytopenia associated with polytrauma

“…The 4Ts scoring system, which assesses thrombocytopenia, the timing of platelet count reductions or thrombosis, thrombosis or other clinical sequelae, and other causes of thrombocytopenia, is widely used for screening . Although HIT can be ruled out when a low 4T score is obtained, definitive diagnoses should be based on a combination of compatible clinical findings and serological testing, including antigen and functional assays, to prevent overdiagnosis . It is recommended to discontinue UFH treatment or switch to argatroban as soon as possible when a moderate to high 4Ts score is obtained.…”

Increased hs-CRP and Sepsis Influence the Occurrence of Thrombocytopenia in Severe and Critically Ill COVID-19 Patients Receiving Anticoagulants

“…For thrombocytopenia risk assessment, the 4T score, which included platelet count, timing of anticoagulant, incidence of thrombosis, and exclusion of other causes of thrombocytopenia, was counted. (22,23) Thrombocytopenia event during 5-14 days after anticoagulant treatment was then evaluated. Data were collected by consecutive sampling on eligible subjects.…”

Laboratory diagnosis of heparin‐induced thrombocytopenia: A retrospective experience

“…Therefore, even though it is recommended to swiftly substitute heparin for another anticoagulant when HIT is suspected, a rapid diagnostic test is desirable. The 4T risk score has an excellent negative predictive value (NPV) for low risk scores (≤3) (NPV ranged from 85% to 99.8% 2 , 3 , 4 , 5 ), but its positive predictive value (PPV) for intermediate or high risk scores remains insufficient 2 , 3 , 5 . Thus, it seems necessary in many cases to confirm or rule out HIT with laboratory assays, such as immunoassays (detection of anti‐PF4 antibodies) or functional assays (detection of platelet activation).…”