What is a 4T (Thrombotic Thrombocytopenic Purpura) panel used for when evaluating platelet function?

From the Guidelines

The 4T score is used to assess the likelihood of heparin-induced thrombocytopenia (HIT) by evaluating four key elements: Thrombocytopenia, Timing, Thrombosis, and other potential causes of thrombocytopenia. The 4T score is a valuable tool in clinical practice, as it helps clinicians make decisions about whether to discontinue heparin therapy and switch to alternative anticoagulants while awaiting confirmatory laboratory testing 1. The score is calculated by assigning a score of 0-2 points for each of the four categories, with a total possible score of 0-8. A low score (0-3) suggests HIT is unlikely, an intermediate score (4-5) indicates moderate probability, and a high score (6-8) suggests HIT is highly likely 1. This scoring system provides a standardized approach to evaluating patients with suspected HIT, helping to avoid both underdiagnosis of a potentially fatal condition and overdiagnosis leading to unnecessary changes in anticoagulation therapy. Some key points to consider when using the 4T score include:

• The score should be calculated based on a thorough evaluation of the patient's clinical presentation and laboratory results 1
• A high-probability 4T score (6-8) suggests HIT is highly likely, and discontinuation of heparin and initiation of a non-heparin anticoagulant at therapeutic intensity is recommended 1
• An intermediate-probability 4T score (4-5) indicates moderate probability, and discontinuation of heparin and initiation of a non-heparin anticoagulant at prophylactic or therapeutic intensity may be considered, depending on the patient's risk of bleeding 1
• A low-probability 4T score (0-3) suggests HIT is unlikely, and HIT laboratory testing and empiric treatment of HIT are not recommended 1. Overall, the 4T score is a useful tool in the diagnosis and management of HIT, and its use can help improve patient outcomes by reducing the risk of thrombosis and bleeding complications.

From the Research

Use of 4T Score in Checking Platelet Stuff

The 4T score is a pretest clinical scoring system used to determine the probability of heparin-induced thrombocytopenia (HIT) in patients with suspected HIT. The score is based on four criteria:

• Thrombocytopenia
• Timing of thrombocytopenia
• Thrombosis
• Other causes of thrombocytopenia 2, 3, 4

Calculation and Interpretation of 4T Score

The 4T score is calculated by assigning points to each of the four criteria, with a total score ranging from 0 to 8. A low probability score (0-3) indicates a low risk of HIT, while an intermediate (4-5) or high (6-8) score indicates a higher risk 2, 3.

Clinical Application of 4T Score

The 4T score is recommended as an initial step in evaluating patients with suspected HIT, prior to laboratory testing 3, 4. A low 4T score can help rule out HIT, while a higher score indicates the need for further evaluation and laboratory testing. The use of the 4T score can help reduce unnecessary laboratory testing and improve patient outcomes 5.

Key Points to Consider

• The 4T score is a useful tool in evaluating patients with suspected HIT
• A low 4T score can help rule out HIT
• Laboratory testing is not recommended for patients with a low 4T score, unless there are missing or unreliable clinical data 3
• The 4T score should be used in conjunction with clinical judgment and laboratory testing to diagnose and manage HIT 2, 3, 4, 6