缺鐵性貧血

Buzzwords → Dx

Diagnostic Criteria

• Ferritin <30 ng/mL (adults) or <100 ng/mL with chronic inflammation/CKD is consistent with IDA.
• Low Fe + high TIBC + low TSAT (<20 %) + ferritin diagnostic = IDA.
• Soluble transferrin receptor (sTfR) + sTfR/log(ferritin) ratio helps distinguish IDA from ACD.
• Hepcidin (research/specialty): low in IDA, high in ACD/CKD/inflammation.
• MCV typically <80 fL but can be normal in early IDA or IDA+ACD overlap.

Workup

• CBC + smear + reticulocyte.
• Iron studies: Fe, TIBC, TSAT, ferritin.
• CRP/ESR (assess inflammation effect on ferritin interpretation).
• Vitamin B12, folate (often coexist).
• Hb electrophoresis if family history or suspecting thalassemia.
• Reticulocyte response at 1 wk after iron initiation (rising = working).
• GI workup in adults:
  • Postmenopausal women, men, premenopausal women without obvious bleeding source: EGD + colonoscopy.
  • Premenopausal women: gynecologic + dietary review first; if unremarkable, GI workup.
• Celiac serology (anti-TTG IgA + total IgA) for refractory IDA — esp. children, adolescents, young adults.
• H. pylori testing if upper GI symptoms or Asian/Mediterranean ancestry.
• Urinalysis (hematuria as occult source).

Treatment Algorithm

flowchart TD
  A[Confirmed IDA<br>ferritin <30 or <100 with inflammation] --> B[Investigate cause<br>GI workup adults; menstrual hx; celiac]
  B --> C{IDA severity / context}
  C -- mild-moderate, asymptomatic --> D[Oral iron<br>ferrous sulfate 65 mg ELEMENTAL<br>ALTERNATE DAYS<br>better absorption + tolerability]
  C -- severe, intolerant of oral, malabsorption,<br>CKD, IBD, post-bariatric --> E[IV iron<br>iron sucrose / ferric carboxymaltose / ferric derisomaltose]
  C -- urgent / Hb <7 + symptomatic --> F[RBC transfusion + IV iron<br>not for asymptomatic anemia]
  D --> G[Reticulocyte response 7-10 d<br>Hb up 1-2 g/dL by 4 wk]
  E --> G
  G -- responding --> H[Continue iron 3-6 mo<br>then check ferritin → goal 50-100 ng/mL]
  G -- non-response --> I[Re-evaluate diagnosis:<br>incorrect dx (thal, ACD, sideroblastic)<br>ongoing GI loss<br>celiac<br>H. pylori<br>IRIDA<br>compliance]

Pearls / Pitfalls

• Alternate-day oral iron absorbs better than daily (Stoffel et al, Lancet Haematol 2017): hepcidin spikes after each dose blunt next-day absorption.
• Take iron with vitamin C (orange juice) on empty stomach; avoid PPIs, calcium, antacids within 2 h.
• PPIs reduce iron absorption — common cause of "refractory" oral iron failure.
• IV iron indications: malabsorption (celiac, IBD, post-bariatric), severe anemia needing rapid response, intolerance to oral, CKD, dialysis, pregnancy 2nd/3rd trimester, peri-op anemia optimization.
• IV iron formulations:
  • Iron sucrose (Venofer): multiple smaller doses; safest
  • Ferric gluconate (Ferrlecit): older, smaller doses
  • Ferric carboxymaltose (Injectafer): single 1000 mg → hypophosphatemia common
  • Ferric derisomaltose (Monoferric): single 1000 mg, lower hypophosphatemia
  • LMW iron dextran (INFeD): historic, test dose required
• Ferritin is an acute-phase reactant — interpret with CRP context. ACD + IDA overlap = ferritin can be 30–200 with TSAT <20 %.
• GI workup in adult IDA is NOT optional — adult-onset IDA without obvious cause requires colonoscopy + EGD (US task force, AGA). Missing colon cancer is a board favorite trap.
• Thalassemia trait vs IDA: thal — high or normal RBC count, target cells, high A₂ on Hb electrophoresis (β-thal trait), normal ferritin.
• Celiac disease is THE differential for refractory IDA in young adults — always check anti-TTG IgA + total IgA to rule out IgA deficiency.
• Helicobacter pylori can cause IDA (autoimmune gastritis, occult bleeding) — eradicate and recheck.
• IRIDA (Iron-Refractory Iron-Deficient Anemia) = TMPRSS6 mutation → high hepcidin → impaired iron absorption. Diagnose with persistently elevated hepcidin in face of IDA. Treat with IV iron (oral fails).
• Pregnancy iron requirement rises 2nd/3rd trimester — universal supplementation in many countries; IV iron preferred if symptomatic anemia despite oral.

Cross-references

• Lab Values — Fe, TIBC, ferritin, TSAT
• Iron Studies — patterns by anemia type
• ACD — DDx
• Thalassemia — DDx
• Anemia Workup algorithm

相關題目

• Q-106 — IDA — adult evaluation requires GI workup
• Q-107 — IDA — alternate-day vs daily oral iron
• Q-108 — IDA — IV iron and hypophosphatemia
• Q-127 — Thalassemia trait vs IDA

Sources