Thrombocytopenia

Symptoms

Superficial bleeding (petechiae, purpura, mucosal bleeding), epistaxis, menorrhagia

Etiology

Category	Conditions
Autoimmune	ITP, SLE, RA
Consumption	HUS/TTP, DIC, HT
Production	Bone marrow failure (presents as pancytopenia), Myelodysplasia, B12/Folate deficiency
Drug induced	NSAIDs, sulfa drugs, IIb/Illa inhibitors, Heparin, Quinine, EtOH
Infection	HIV, Hep C, EBV
Genetic	Bernard Soulier (AR Defect in GPIb-IX), Glanzmann Thrombasthenia (AR Defect in GPIIb-Illa)
Sequestration	Seen with hypersplenism, portal hypertension
Pseudo	Pseudothrombocytopenia (platelet clumping, resulting in abnormal test)
Special Scenarios	Malignancy (bone marrow invasion or DIC), Pregnancy (gestational thrombocytopenia, preeclampsia, HELLP), Liver failure (I TPO, splenic sequestration)
Uniat Superficial bleeding	Petechiae, purpura, mucosal bleeding, epistaxis, menorrhagia

Investigations

Exam for signs of bleeding
CBC in citrated blood tube, INR, PTT, fibrinogen, D-dimer, blood smear
Additional considerations: Heparin-PF4 antibody (if 4T-score is 4-8), ultrasonography for DVT evaluation, ferritin (if concern for HLH), liver function tests (if cirrhosis suspected), TEG in complex cases

Immediate concerns

Evaluate risk of bleeding: Review anticoagulant medications, consider discontinuation, and platelet transfusion if necessary
Consider HIT (Heparin-Induced Thrombocytopenia)
If schistocytes are present, consider TTP (Thrombotic Thrombocytopenic Purpura)

Treatment

Heparin Induced Thrombocytopenia

Etiology

HIT results from autoantibodies that react to a combination of heparin and platelet factor 4 (PF4), leading to platelet activation and thrombosis
Risk factors include female sex, older age, obesity, and hemodialysis
Consider HIT in patients recently treated with heparin who have new-onset thrombocytopenia, skin necrosis at injection sites, anaphylactoid response to heparin, or venous/arterial thrombosis

Risk Stratification and Diagnostic Tests for HIT

Use the 4T score for risk stratification
The heparin-PF4 antibody test has high sensitivity but poor specificity
Serotonin Release Assay (SRA) is the gold standard diagnostic test, but it is expensive and time-consuming

Management and Treatment of HIT

Initiate empiric anticoagulation therapy for HIT in patients with clinical thrombosis on therapeutic heparin anticoagulation
Switch heparin to a non-heparin agent such as argatroban
For patients without clinical thrombosis but a high likelihood of HIT, empiric anticoagulation with a non-heparin agent should generally be started before confirmation of the diagnosis
Non-heparin anticoagulants
- Argatroban is perhaps most commonly used (with a similar option being Bivalirudin)
- Fondaparinux could be considered in intermediate-likelihood situations, at a reduced dose (2.5 mg sq daily)

4Ts Score for Heparin-Induced Thrombocytopenia