Stethopedia | Approach

Approach to

Anemia

Check stability and the other cell lines, let the reticulocyte index split underproduction from blood loss or hemolysis, then use the MCV, iron studies or hemolysis labs to name the cause.

  1. Hb <130 g/L (men) or <120 g/L (women), or a fall from baseline
  2. Bleeding, diet, drug, alcohol history; CBC with MCV, RDW, other cell lines vs prior; smear11
  3. Reticulocyte index; draw iron, B12, folate, hemolysis labs and T&S before transfusing11
  4. Unstable, bleeding or hemolyzing?

Unstable: resuscitate; urgent GI or hematology8,11

  • Shock: low BP, tachycardia
  • Angina or dyspnea at rest
  • Pancytopenia or blasts on smear
  • Melena, hematemesis or BRBPR
  • Schistocytes, low platelets: TTP?
  • Fast Hb fall, jaundice, dark urine

→ Bleed/shock: transfuse now, not by Hb; MI: consider <100 g/L9,11

If not: reticulocyte index, then MCV?

CausesCluesWorkupManagement

Microcytic (RI <2%)

  • Iron deficiency: blood loss, malabsorption
  • Occult GI cancer causing iron loss
  • Inflammation; thalassemia trait; lead
  • Pica, koilonychia, restless legs4
  • Menorrhagia, melena, NSAIDs; celiac
  • Mentzer (MCV/RBC) <13: thalassemia11
  • Ferritin <45 µg/L (<100 if inflamed)2,4
  • tTG; men/postmeno: EGD/colonoscopy2,3
  • Fe replete: Hb electrophoresis, lead11
  • Elemental Fe 50–100 mg daily/QOD3,5
  • IV iron if intolerant, malabsorption3,11
  • Treat source; iron 3 mo past Hb normal3

Normocytic (RI <2%)

  • Inflammation, CKD, endocrine
  • Acute bleed before retics rise
  • Marrow failure, myeloma, infiltration
  • Anticoagulant, procedure, falling Hb
  • High RDW: mixed deficiency11
  • Other cytopenias, bone pain, high Ca
  • Serial Hb, creatinine, TSH, CRP, iron11
  • SPEP + free light chains if unexplained11
  • Marrow biopsy if cytopenias or blasts11
  • Treat cause; iron if also deficient11
  • CKD: nephrology for iron ± ESA11
  • Marrow failure: urgent hematology11

Macrocytic (RI <2%)

  • B12 deficiency: pernicious anemia
  • Folate lack; alcohol; liver disease
  • MTX, hydroxyurea, MDS, thyroid
  • Paresthesias, ataxia, low vibration6
  • Hypersegmented neutrophils11
  • Vegan, gastrectomy, PPI, metformin6
  • B12, folate, TSH, LFTs; drug review11
  • Borderline B12: MMA ± homocysteine6,11
  • Low B12: anti-intrinsic factor Ab11
  • B12 1 mg IM if neuro, else 1–2 mg PO/d6
  • Folate 1–5 mg/d once B12 replete6,11
  • MDS suspected: hematology referral

Hemolysis or blood loss

  • Bleeding: GI, retroperitoneal
  • TTP/HUS/DIC; autoimmune hemolysis
  • G6PD, sickle cell, spherocytosis, valve
  • Jaundice, dark urine, splenomegaly11
  • Schistocytes + low platelets: TMA11
  • Spherocytes: AIHA or hereditary7,11
  • LDH, bilirubin, haptoglobin, DAT, UA11
  • Schistocytes: PLASMIC, ADAMTS138,11
  • Bleed: endoscopy or CT angiography
  • TTP: PLEX, steroids; avoid platelets10,11
  • Warm AIHA: steroids; call blood bank7,11
  • Bleed: stop source; transfuse by need11

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

References

  1. Carson JL, Stanworth SJ, Guyatt G, et al. Red blood cell transfusion: 2023 AABB international guidelines. JAMA. 2023;330:1892–1902. PubMed 37824153
  2. Ko CW, Siddique SM, Patel A, et al. AGA clinical practice guidelines on the gastrointestinal evaluation of iron deficiency anemia. Gastroenterology. 2020;159:1085–1094. PubMed 32810434
  3. Snook J, Bhala N, Beales ILP, et al. British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults. Gut. 2021;70:2030–2051. PubMed 34497146
  4. Camaschella C. Iron-deficiency anemia. N Engl J Med. 2015;372:1832–1843. PubMed 25946282
  5. Stoffel NU, Cercamondi CI, Brittenham G, et al. Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women. Lancet Haematol. 2017;4:e524–e533. PubMed 29032957
  6. Stabler SP. Clinical practice. Vitamin B12 deficiency. N Engl J Med. 2013;368:149–160. PubMed 23301732
  7. Brodsky RA. Warm autoimmune hemolytic anemia. N Engl J Med. 2019;381:647–654. PubMed 31412178
  8. 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
  9. Carson JL, Brooks MM, Hébert PC, et al. Restrictive or liberal transfusion strategy in myocardial infarction and anemia. N Engl J Med. 2023;389:2446–2456. PubMed 37952133
  10. 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
  11. Kendall E, Selesky M, Gutierrez Moore C, eds. Pancytopenia & Anemia; Thrombocytopenia; Transfusion Medicine; Peripheral Smear Interpretation. In: Department of Medicine Housestaff Manual, 30th ed. 2024:133–134, 136, 141, 144.

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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