What labs should be drawn in a child with suspected iron overload (hyperferremia)?

Laboratory Evaluation for Suspected Iron Overload in Children

In a child with suspected iron overload, immediately obtain serum ferritin and fasting transferrin saturation as the initial screening tests, followed by HFE genetic testing (C282Y and H63D mutations) if transferrin saturation is elevated (>45%), and consider additional testing including complete blood count, liver enzymes, and inflammatory markers to distinguish true iron overload from secondary causes of hyperferritinemia. 1

Initial Screening Panel

Core Iron Studies:

• Serum ferritin - the primary marker of total body iron stores, though it acts as an acute phase reactant and can be elevated in inflammation, infection, liver disease, and malignancy 1, 2
• Fasting transferrin saturation (TSAT) - calculated as serum iron/total iron binding capacity × 100, provides insight into circulating iron available for tissues and helps distinguish true iron overload from hyperferritinemia without iron overload 1, 3, 2

Interpretation thresholds: Transferrin saturation >45% in females or >50% in males, combined with elevated ferritin, suggests true iron overload requiring further investigation 1

Essential Confirmatory and Differential Testing

When transferrin saturation is elevated (>45%):

• HFE genetic testing for C282Y and H63D mutations to diagnose hereditary hemochromatosis, the most common genetic iron overload disorder 1, 2
• Diagnosis requires both C282Y homozygosity (or compound heterozygosity) AND evidence of increased iron stores, not genotype alone 1

Complete blood count with indices to evaluate for:

• Hemoglobin and hematocrit levels
• Mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH)
• Red cell distribution width (RDW)
• These help identify underlying hematologic disorders causing secondary iron overload such as thalassemia, myelodysplastic syndrome, or sickle cell disease 1, 2, 4

Distinguishing True Iron Overload from Hyperferritinemia

Mandatory tests to identify common causes of hyperferritinemia WITHOUT iron overload:

• C-reactive protein (CRP) - to detect inflammation 1
• Liver enzymes (AST, ALT) - to identify hepatocellular injury or chronic liver disease 1, 2
• Creatine kinase (CK) - to detect muscle cell necrosis 1

Over 90% of hyperferritinemia cases are explained by chronic alcohol consumption, inflammation, cell necrosis, tumors, or metabolic syndrome rather than true iron overload 1

Additional Specialized Testing

When initial screening suggests iron overload:

• Liver MRI with iron quantification (T2)* - non-invasive assessment of hepatic iron concentration, particularly useful when diagnosis is unclear or to quantify iron burden 1
• Soluble transferrin receptor (sTfR) - reflects tissue iron demands and bone marrow activity, useful in complex cases but may not be elevated in iron-deficient infants <1 year 1

For suspected non-HFE hemochromatosis (rare):

• Genetic testing of TFR2, SLC40A1, HAMP, and HJV genes should only be considered after excluding C282Y homozygosity and confirming iron excess by direct assessment (MRI or biopsy) 1

Liver Assessment in Confirmed Iron Overload

Liver biopsy indications (not for diagnosis of iron overload itself):

• Serum ferritin >1,000 μg/L
• Elevated liver enzymes
• Hepatomegaly
• Age >40 years (less relevant in pediatrics)
• Primary purpose is to assess for cirrhosis or advanced fibrosis 1

Non-invasive fibrosis assessment:

• Transient elastography can rule out advanced fibrosis if liver stiffness <6.4 kPa 1
• FIB-4 score has limited validation in hemochromatosis but may be considered 1

Critical Pitfalls to Avoid

• Do not diagnose hemochromatosis based on C282Y homozygosity alone - requires documented evidence of increased iron stores 1
• Do not overlook inflammatory markers - ferritin can be markedly elevated from inflammation, infection, or malignancy without true iron overload 1
• Do not assume normal transferrin saturation excludes iron overload - low or normal TSAT with high ferritin should prompt evaluation for secondary causes including dysmetabolic iron overload syndrome, chronic liver disease, or ferroportin disease 3, 2, 5
• Do not test for rare hemochromatosis genes prematurely - only pursue after excluding HFE mutations and confirming true iron excess by direct measurement 1
• Do not forget to screen siblings - they have a 25% chance of being C282Y homozygotes if the index patient has HFE-related hemochromatosis 1

Monitoring Parameters During Treatment

For children receiving iron chelation therapy:

• Serum ferritin and hemoglobin monthly 1, 6
• Serum creatinine (duplicate measurements) and estimated GFR at baseline, weekly for first month, then monthly 6
• Liver transaminases and bilirubin every 2 weeks during first month, then monthly 6
• Urinalysis and serum electrolytes to evaluate renal tubular function 6