What initial blood tests should be ordered to diagnose hemochromatosis in a patient with suspected iron overload?

Initial Blood Tests for Hemochromatosis Diagnosis

The initial diagnostic approach requires simultaneous measurement of transferrin saturation (TS) and serum ferritin—never rely on a single test—with TS ≥45% and elevated ferritin (>300 μg/L in men, >200 μg/L in women) triggering HFE genetic testing for C282Y and H63D mutations. 1

Primary Screening Tests

The essential initial laboratory panel includes:

• Transferrin saturation (TS): Calculated from serum iron divided by total iron-binding capacity (TIBC), with a diagnostic threshold of ≥45% 1
• Serum ferritin: Must be measured simultaneously with TS rather than sequentially 1, 2
• Complete blood count with reticulocytes: To exclude anemia and red cell disorders that may confound interpretation 1

The transferrin saturation is the most sensitive early marker for hemochromatosis and typically becomes abnormal before ferritin elevation occurs. 1 However, both tests together provide optimal diagnostic accuracy, as a normal TS with elevated ferritin may still indicate non-HFE hemochromatosis or compound heterozygosity. 1, 2

Interpretation and Next Steps

If either TS ≥45% or ferritin exceeds normal limits, proceed immediately to HFE genetic testing for C282Y and H63D mutations. 1, 2 This represents the most cost-effective diagnostic pathway, as C282Y homozygosity accounts for 85-90% of clinically affected patients of European ancestry. 1, 2

Critical Diagnostic Thresholds:

• Males: TS >50% and/or ferritin >300 μg/L warrants genetic testing 1, 3
• Females: TS >45% and/or ferritin >200 μg/L warrants genetic testing 1, 3
• Both sexes: Persistently elevated TS ≥45% requires genetic evaluation 1, 2

Assessment of Disease Severity

Once iron overload is confirmed, additional tests assess hepatic involvement and cirrhosis risk:

• Liver function tests (ALT, AST): Ferritin >1,000 μg/L combined with elevated transaminases and platelet count <200 predicts cirrhosis in approximately 80% of C282Y homozygotes 1, 2
• Platelet count: Values <200 combined with elevated ferritin indicate high cirrhosis risk 2
• Ferritin <1,000 μg/L with normal transaminases and no hepatomegaly: Accurately excludes advanced fibrosis and cirrhosis 1, 2

Important Caveats and Pitfalls

Serum ferritin has significant false-positive rates due to inflammation, making it less specific than TS. 1 Ferritin can be falsely elevated in:

• Necroinflammatory liver disease (alcoholic liver disease, chronic hepatitis B/C, NAFLD) 1
• Malignancy and lymphomas 1
• Chronic inflammatory conditions 1
• Metabolic syndrome 1, 2

Before attributing elevated iron studies to hemochromatosis, exclude these secondary causes of hyperferritinemia. 1, 3 In the general population, iron overload is not the most common cause of elevated ferritin. 1

Fasting samples are no longer required for initial screening, as recent studies show no improvement in sensitivity or specificity for detecting C282Y homozygotes with fasting versus non-fasting specimens. 1 However, confirming an elevated TS with a second determination remains advisable. 1

When Genetic Testing is Negative

If HFE testing is uninformative but iron overload is suspected, further genetic testing should only be pursued after confirming true iron overload by measuring hepatic iron concentration through liver biopsy or MRI. 4 In patients of non-European ancestry with elevated iron parameters, the pre-test probability of C282Y mutation is very low, and direct sequencing of a broader gene panel (HFE, HJV, TFR2, CP, SLC40A1) may be considered. 1