In a child with a transferrin saturation of 20%, what is the appropriate management—iron supplementation or dietary monitoring with repeat iron studies?

Management of TSAT 20% in Children

In a child with transferrin saturation of 20%, iron supplementation is indicated, as this threshold represents the lower limit of adequacy and signals high likelihood of iron deficiency requiring treatment. 1

Diagnostic Interpretation

A TSAT of exactly 20% in children sits at a critical diagnostic threshold:

• TSAT ≤20% indicates iron-deficient erythropoiesis and warrants iron supplementation, as this level reflects insufficient iron availability for red blood cell production 2, 1
• In children aged 0.5-12 years, TSAT values are physiologically lower than adults, making the 20% threshold even more significant 3, 4
• TSAT <16% in children without inflammation confirms absolute iron deficiency, though the 20% cutoff is used as the treatment threshold to prevent progression 2, 1
• Approximately 20% of iron-replete children have TSAT values <15%, but a value at exactly 20% combined with any clinical concern (anemia, symptoms, or risk factors) should prompt treatment 4

Required Additional Laboratory Evaluation

Before initiating treatment, obtain:

• Serum ferritin to distinguish absolute from functional iron deficiency 2, 1
• Complete blood count (CBC) with hemoglobin, hematocrit, and mean corpuscular volume (MCV) to assess severity 1
• Inflammatory markers (CRP, ESR) if chronic disease is suspected, as inflammation elevates ferritin and complicates interpretation 1

Interpretation Algorithm Based on Ferritin

• Ferritin <30 ng/mL + TSAT 20%: Absolute iron deficiency → oral iron supplementation 1
• Ferritin 30-100 ng/mL + TSAT 20%: Possible functional iron deficiency or early depletion → oral iron trial, investigate for chronic inflammation 1
• Ferritin >100 ng/mL + TSAT 20%: Functional iron deficiency in setting of chronic disease → consider IV iron if underlying condition identified 2, 1

Treatment Recommendations

Oral Iron Supplementation (First-Line)

• Elemental iron 3-6 mg/kg/day divided into 1-2 doses for children without chronic kidney disease or inflammatory conditions 2
• Administer between meals to maximize absorption, though with meals if gastrointestinal side effects occur 2
• Continue for 3 months after hemoglobin normalizes to replete iron stores 2

Monitoring Response

• Recheck CBC and iron parameters (ferritin, TSAT) at 4-8 weeks after initiating oral iron 1
• Expect hemoglobin increase of 1-2 g/dL within 4-8 weeks if treatment is effective 1
• Target TSAT ≥20% and ferritin ≥30-45 ng/mL in children without chronic inflammatory conditions 1

When to Consider IV Iron

• Chronic kidney disease patients on hemodialysis: TSAT ≤20% warrants IV iron, as oral iron is inadequate in this population 2, 5
• Failure to respond to oral iron after 8 weeks of adequate supplementation 1
• Chronic inflammatory conditions (inflammatory bowel disease, chronic infections) where hepcidin blocks oral iron absorption 1
• In pediatric hemodialysis patients, IV iron dextran 4 mg/kg (maximum 100 mg) per dialysis session for 10 consecutive sessions has demonstrated efficacy 5

Common Pitfalls and Caveats

• Do not rely on TSAT alone: Always interpret alongside ferritin, as TSAT has greater day-to-day variation than hemoglobin 2, 1
• Avoid measuring iron parameters within 4 weeks of IV iron administration, as circulating iron interferes with assays and produces falsely elevated results 1
• In children with chronic disease, ferritin up to 100 ng/mL may still indicate true iron deficiency despite appearing "normal," because inflammation artificially elevates ferritin 1
• TSAT <16% combined with anemia and low MCV provides stronger evidence of iron deficiency in children aged 0.5-12 years than TSAT alone 3
• Transferrin saturation is unsuitable as a single diagnostic criterion in children and must be combined with other iron status indicators 4

Investigation for Underlying Causes

In children with confirmed iron deficiency:

• Assess dietary iron intake: inadequate intake is the most common cause in children <2 years 2
• Evaluate for chronic blood loss: gastrointestinal bleeding, heavy menstrual bleeding in adolescent females 1
• Screen for malabsorption: celiac disease, inflammatory bowel disease 1
• Consider chronic inflammatory conditions: chronic kidney disease, chronic infections 1