Stethopedia | Approach

Approach to

Thrombocytopenia

Confirm the count is real, act first on bleeding, HIT and thrombotic microangiopathy, then sort by mechanism: low production, immune destruction, consumption or sequestration. ITP is a diagnosis of exclusion.

  1. Platelets <150 ×10⁹/L, or a fall from baseline
  2. Bleeding history and exam; heparin and drug review; prior counts; smear, citrate tube if clumps8
  3. CBC, creatinine, LFTs, PT/aPTT, fibrinogen, HIV, HCV, β-hCG, type and screen8
  4. Bleed, HIT, TMA, DIC, blasts or HELLP?

Emergency: treat now; call hematology8

  • Major bleed; headache: CT head
  • Heparin and fall >50%: suspect HIT
  • Schistocytes: TTP until excluded
  • Long PT/aPTT, low fibrinogen: DIC
  • Blasts or pancytopenia on smear
  • Pregnant: HELLP or preeclampsia

→ 4Ts ≥4: non-heparin AC; high PLASMIC: PLEX; major bleed: plt1,3,8

If not: which mechanism?

CausesCluesWorkupManagement

Low production

  • Leukemia, MDS, marrow infiltration
  • Sepsis; viral: HIV, HCV, EBV, CMV
  • Alcohol, B12 or folate lack, chemo
  • Other cytopenias; blasts on smear8
  • Alcohol use, poor diet; macrocytosis
  • Fever, bone pain, B symptoms
  • B12, folate, HIV, HCV8
  • Marrow biopsy if other lines low8
  • Treat cause; stop marrow toxins
  • No bleed, chemo: platelets if <10 ×10⁹/L7
  • Marrow disease: urgent hematology8

Immune destruction

  • HIT: any heparin, even flushes
  • Drugs: quinine, antibiotics, ASMs
  • ITP (exclusion); SLE, APS, lymphoma
  • Heparin d5–10; <24 h if ≤100 d prior1,8
  • New drug; sudden, deep fall8
  • Well; isolated; large platelets8
  • 4Ts; anti-PF4 only if ≥41,2
  • ANA, aPL if SLE or APS suspected8
  • Stop drug; HIT: argatroban/fonda/DOAC1,8
  • ITP <30: steroids + ritux or TPO-RA6
  • ITP critical bleed: plt, IVIG, steroid, TXA9

Consumption

  • TTP; HUS (Shiga toxin, complement)
  • DIC: sepsis, cancer, trauma, obstetric
  • HELLP; ECMO, balloon pump, valves
  • Schistocytes, high LDH, low haptoglobin8
  • TTP: plt <30 ×10⁹/L, neuro signs, fever8
  • Bloody diarrhea, then AKI: ST-HUS8
  • PLASMIC; ADAMTS13 before PLEX3,4
  • DAT, D-dimer; stool Shiga toxin if diarrhea8
  • TTP: PLEX, steroid, ritux, caplacizumab5,11
  • DIC: fix cause; plt <10, <50 if bleeding7,12
  • TTP: no platelets unless major bleed8

Sequestration, dilution

  • Hypersplenism: cirrhosis, portal HTN
  • Massive transfusion; hypothermia
  • Gestational thrombocytopenia
  • Splenomegaly; stigmata of liver disease
  • Pregnant, well, normal BP; plt ≥10010
  • Ultrasound: spleen, liver
  • Pregnant: BP, urine protein, LFTs
  • Treat cause; usually observe
  • Major surgery: platelets if <50 ×10⁹/L7

Can't-miss cause Superscripts link to the references below.

References

  1. Cuker A, Arepally GM, Chong BH, et al. American Society of Hematology 2018 guidelines for management of venous thromboembolism: heparin-induced thrombocytopenia. Blood Adv. 2018;2:3360–3392. PubMed 30482768
  2. Cuker A, Gimotty PA, Crowther MA, Warkentin TE. Predictive value of the 4Ts scoring system for heparin-induced thrombocytopenia: a systematic review and meta-analysis. Blood. 2012;120:4160–4167. PubMed 22990018
  3. Bendapudi PK, Hurwitz S, Fry A, et al. Derivation and external validation of the PLASMIC score for rapid assessment of adults with thrombotic microangiopathies: a cohort study. Lancet Haematol. 2017;4:e157–e164. PubMed 28259520
  4. Zheng XL, Vesely SK, Cataland SR, et al. ISTH guidelines for the diagnosis of thrombotic thrombocytopenic purpura. J Thromb Haemost. 2020;18:2486–2495. PubMed 32914582
  5. Zheng XL, Vesely SK, Cataland SR, et al. ISTH guidelines for treatment of thrombotic thrombocytopenic purpura. J Thromb Haemost. 2020;18:2496–2502. PubMed 32914526
  6. Cuker A, Terrell DR, Sowdagar H, et al. American Society of Hematology 2026 guidelines for immune thrombocytopenia: initial and second-line therapy for adults with primary ITP. Blood Adv. 2026;10:7076–7097. PubMed 42617047
  7. Metcalf RA, Nahirniak S, Guyatt G, et al. Platelet transfusion: 2025 AABB and ICTMG international clinical practice guidelines. JAMA. 2025;334:606–617. PubMed 40440268
  8. Somasundaram E, Trad N, Gutierrez Moore C, eds. Thrombocytopenia; Coagulation Disorders; Peripheral Smear Interpretation. In: Department of Medicine Housestaff Manual, 30th ed. 2024:136, 138, 144.
  9. Chowdhury SR, Sirotich E, Guyatt G, et al. Guideline on the emergency management of critical bleeding in patients with immune thrombocytopenia. Blood Adv. 2026;10:5558–5575. PubMed 41637560
  10. Reese JA, Peck JD, Deschamps DR, et al. Platelet counts during pregnancy. N Engl J Med. 2018;379:32–43. PubMed 29972751
  11. Zheng XL, Al-Housni Z, Cataland SR, et al. 2025 focused update of the 2020 ISTH guidelines for management of thrombotic thrombocytopenic purpura. J Thromb Haemost. 2025;23:3711–3732. PubMed 40533296
  12. Levi M, Toh CH, Thachil J, Watson HG. Guidelines for the diagnosis and management of disseminated intravascular coagulation. British Committee for Standards in Haematology. Br J Haematol. 2009;145:24–33. PubMed 19222477

For education only; not a substitute for clinical judgment or local protocols. Where sources differ, the flowchart follows the current guideline.

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