Thrombocytopenia

Aka: Thrombocytopenia, Low Platelets, Low Platelet Count

1. Definition
   1. Decreased Platelet Count below 100k to 150k
2. See Also
   1. Thrombocytopenia Causes
   2. Platelet Dysfunction
   3. Purpura
3. History
   1. Family History of Thrombocytopenia
      1. Consider congenital Thrombocytopenia Causes
   2. Comorbid conditions
      1. Liver disease
      2. Heart Valve Replacement
   3. Pregnancy
      1. Gestational Thrombocytopenia
      2. Preeclampsia with HELLP Syndrome
   4. Social history
      1. Alcohol Abuse
   5. Recent viral infection
      1. Immune Thrombocytopenia (ITP) in children follows acute viral infection by days to weeks
      2. Cytomegalovirus (CMV)
      3. Epstein Barr Virus (EBV, Mononucleosis)
      4. Varicella Zoster Virus (VZV, Chicken Pox)
      5. Parvovirus B19
      6. HIV Infection
      7. Hepatitis C
   6. Tick Bite
      1. Anaplasmosis
      2. Babesiosis
      3. Rocky Mountain Spotted Fever
      4. Lyme Disease
   7. Recent international travel (especially tropical)
      1. Dengue Fever
      2. Malaria
      3. Rickettsial Disease
   8. Medications
      1. Drug-Induced Thrombocytopenia
      2. Heparin-Induced Thrombocytopenia
      3. Chemotherapy
      4. Radiation Therapy
      5. Immunizations (MMR, Varicella, H1N1 Influenza Vaccine)
      6. Transfusion
         1. Transfusion Reaction
         2. Infection (Hepatitis C or HIV Infection)
4. Symptoms: Clues to Thrombocytopenia Causes
   1. Abdominal Pain
      1. HELLP Syndrome (pregnancy)
      2. Hemolytic Uremic Syndrome (HUS)
      3. Platelet Sequestration (Splenomegaly)
   2. Bloody Diarrhea
      1. Hemolytic Uremic Syndrome (HUS)
   3. Fever
      1. Viral Infections (e.g. CMV, EBV, VZV, HIV, HCV, Parvovirus B19)
      2. Tick Borne Illness ()
      3. Dengue Fever
      4. Malaria
      5. Rickettsial Disease
      6. Hemolytic Uremic Syndrome (HUS)
      7. Thrombotic Thrombocytopenic Purpura (TTP)
   4. Weight loss or Night Sweats
      1. HIV Infection
      2. Leukemia
      3. Myelodysplastic Syndrome
5. Exam
   1. Complete exam to identify underlying cause (see below)
   2. Deep bleeding (e.g. hemarthrosis) suggest clotting disorder, not Thrombocytopenia
   3. Signs of bleeding (mucosal and superficial bleeding)
      1. Petechiae
      2. Purpura
      3. Gingival Bleeding
      4. Gastrointestinal Bleeding
      5. Urinary tract bleeding
6. Signs: Clues to Thrombocytopenia Causes
   1. Rash
      1. Viral Exanthems (VZV, Parvovirus B19)
      2. Rickettsial infections
      3. Systemic Lupus Erythematosus
   2. Generalized Lymphadenopathy
      1. Viral Infections (e.g. CMV, EBV, HIV)
      2. Systemic Lupus Erythematosus
      3. Leukemia, Lymphoma and other hematiologic malignancies
   3. Hepatomegaly
      1. Chronic Liver Disease
      2. Leukemia
      3. Viral Infections (CMV, EBV, HCV)
   4. Splenomegaly
      1. Viral Infections (CMV, EBV)
   5. Neurologic findings
      1. Thrombotic Thrombocytopenic Purpura (TTP)
   6. Renal Failure
      1. Thrombotic Thrombocytopenic Purpura (TTP)
      2. Hemolytic Uremic Syndrome (HUS)
7. Causes
   1. See Thrombocytopenia Causes
   2. Categories of Thrombocytopenia
      1. Decreased Platelet production (e.g. viral infection, medications, radiation, B12 Deficiency, marrow infiltration)
      2. Increased Platelet destruction (e.g. ITP, TTP, HUS, DIC)
      3. Platelet loss
      4. Splenic Sequestration
8. Labs: Platelet Count Interpretation
   1. Platelet Count 70,000 to 150,000 per uL
      1. Mild Thrombocytopenia
   2. Platelet Count 50,000 to 70,000 per uL
      1. Asymptomatic Moderate Thrombocytopenia
   3. Platelet Count 30,000 to 50,000 per uL
      1. Symptomatic Moderate Thrombocytopenia with excessive bleeding on Traumatic Injury
   4. Platelet Count 30,000 to 50,000 per uL
      1. Symptomatic Moderate Thrombocytopenia with excessive bleeding on Traumatic Injury
   5. Platelet Count 10,000 to 30,000 per uL
      1. Severe Thrombocytopenia with excessive bleeding with minimal Skin Trauma
   6. Platelet Count 5,000 to 10,000 per uL
      1. Severe Thrombocytopenia with risk of spontaneous bleeding, Bruising or Petechiae
      2. Spontaneous bleeding requiring intervention (e.g. Nasal Packing for Epistaxis) required in 42% of patients
   7. Platelet Count below 5,000 per uL
      1. Emergent Thrombocytopenia with high risk of major spontaneous bleeding (e.g. gastrointestinal tract, genitourinary tract)
9. Labs: Initial Evaluation of Thrombocytopenia
   1. Complete Blood Count (CBC)
   2. Basic chemistry panel (chem8)
      1. Evaluate for associated Renal Failure (e.g. TTP, HUS)
      2. Expand to comprehensive panel in Hemolysis
         1. Indirect Bilirubin increased in Hemolysis
         2. Serum Lactate Dehydrogenase and Haptoglobin increased in HUS and TTP
   3. Coagulation tests (INR, PTT, Fibrinogen)
      1. Normal in isolated Thrombocytopenia, ITP, TTP, HUS
      2. Prolonged in DIC, liver disease, Massive Transfusion and Trauma
      3. Fibrinogen is decreased in DIC and Trauma
   4. Peripheral Blood Smear
      1. See Platelet Morphology
      2. See Peripheral Blood Smear
      3. Schistocytes are present in DIC and Microangiopathic Hemolytic Anemia (TTP, HUS), but not ITP
      4. Consider Parasite stains (Tick Borne Illness, Malaria)
      5. Hemolysis will raise Indirect Bilirubin
   5. Platelet Count
      1. Rule-out Pseudothrombocytopenia
         1. Review Peripheral Smear to evaluate for clumping (Pseudothrombocytopenia)
         2. Repeat Platelet Count in non-EDTA Anticoagulant (citrate, blue tube)
      2. Repeat Platelet Count timing (adjust based on chronicity, stability and bleeding complications)
         1. Repeat immediately for developing bleeding complications
         2. Repeat in days to 1 week if Platelet Count <50,000 per uL
         3. Repeat in 2 weeks if Platelet Count <100,000 per uL
         4. Repeat in 4 weeks if Platelet Count <150,000 per uL
10. Management: General Approach
    1. Red Flag Findings accompanying Thrombocytopenia indicating Hematology Referral
       1. Leukopenia or Leukocytosis
       2. Anemia
       3. Peripheral Blood Smear abnormalities
       4. Symptomatic Thrombocytopenia with Bleeding Diathesis, Petechiae, Purpura or Ecchymosis
       5. Platelet Count <50,000 per uL (or persistently below 100,000 per uL on repeat testing)
    2. Conditions requiring emergent management
       1. Heparin Induced Thrombocytopenia (HIT)
       2. Thrombotic Thrombocytopenic Purpura (TTP)
       3. Hemolytic Uremic Syndrome (HUS)
       4. Preeclampsia with HELLP Syndrome
    3. Disposition home
       1. Isolated Thrombocytopenia >30,000/mm3 without signs of bleeding in children
       2. Isolated Thrombocytopenia >30,000 to 50,000/mm3 without signs of bleeding in adults
       3. No serious cause suspected of Thrombocytopenia (i.e. not HUS, TTP, HIT, DIC)
          1. Less severe causes include ITP and Drug induced Thrombocytopenia
       4. Reliable patient or family
          1. No NSAIDS
          2. Follow activity restrictions as below
    4. Management precautions
       1. Avoid platalet transfusion in Hemolytic Uremic Syndrome, Thrombotic Thrombocytopenic Purpura
       2. Avoid Corticosteroids in suspected malignancy (until cancer evaluation and staging)
11. Management: Activity and Procedure Limitations
    1. Platelet Count >50,000 per uL
       1. No limitations to activity or procedures
       2. Use caution in Collision Sports with Thrombocytopenia
       3. Most surgical procedures can be perfromed safely at this Platelet Count
       4. Epidural Anesthesia is safe at 50,000 per uL, but >100,000 per uL is preferred
    2. Platelet Count >20,000 per uL
       1. Bone Marrow Biopsy, bronchoscopy and endoscopy can be performed
    3. Platelet Count <10,000 per uL
       1. Avoid Collision Sports and other activities with risk of Traumatic Injury
12. References
    1. Merrill and Gillen (2016) Crit Dec Emerg Med 30(3): 3-8
    2. Gauer (2012) Am Fam Physician 85(6): 612-22 [PubMed]
    3. George (2000) Lancet 355(9214):1531-9 [PubMed]
    4. Goldstein (1996) Am Fam Physician 53(3):915-20 [PubMed]
    5. Rizvi (1999) Curr Opin Hematol 6(5):349-53 [PubMed]