Haematinic Tests: Changes to Reference Ranges and Comments

Lab Update 56: Haematinic Tests

1. Updated Reference Ranges for Iron Studies

Ferritin

• Lower reference limit changed to 30 µg/L
• Units updated from ng/mL --> µg/L

Transferrin Saturation (TS)

• New lower reference limit: 20%

These changes are based on expert consensus due to previous ranges being clinically inappropriate.

2. Iron Profile & Inflammation

Key Concepts

• Ferritin ↑ with inflammation (positive acute-phase protein)
• Transferrin ↓ with inflammation (negative acute-phase protein)

Iron Deficiency (ID) may be masked in chronic conditions like:

• Obesity
• Diabetes
• Heart failure
• Inflammatory bowel disease

Diagnostic Tips

• In inflammation: Ferritin 100 µg/L + TS20% → ID likely
• In chronic inflammation: Even Ferritin > 100 µg/L + TS20% → ID possible

Additional Tests to Confirm ID

• Soluble Transferrin Receptor (STFR) ↑
• Reticulocyte Hb Content (RET) ↓

3. Folate & Vitamin B12 Interpretation

Vitamin B12

• Always test in megaloblastic anaemia or if neurological symptoms are present

Folate

• Test in high-risk groups:
  • ‍GI conditions
  • Excess alcohol
  • Poor diet

Borderline Results?

• Use Homocysteine and Methylmalonic Acid (MMA) to clarify:
  • Both ↑ → B12 deficiency
  • Homocysteine ↑ + MMA normal → Folate deficiency

False Normal B12

• May occur with elevated transcobalamin due to:
  • Malignancies
  • Liver disease
  • Autoimmune disorders

False Low B12

• Seen in:
  • Multiple myeloma
  • HIV
  • Pregnancy
  • Oral contraceptives, phenytoin

4. Folate Testing: Serum vs Red Cell

Serum Folate

• Affected by recent supplement intake
• Preferred test for folate deficiency
• Better for:
  • B12 deficiency
  • NTD risk in pregnancy
  • Pre-dialysis haemodialysis
  • Capecitabine toxicity risk

Red Cell Folate

• Better for long-term folate status
• Preferred in:
  • Post-dialysis haemodialysis
  • Long-term NTD risk (non-pregnant)
  • Unresolved anaemia

📞 Need help? Contact your local Ampath representative.

References

1. Naveed K et al., 2023 – Ferritin decision limits
2. Simmonds WM et al., 2024 – Iron deficiency in sub-Saharan Africa
3. Means RT & Fairfield KM – Vitamin B12 & Folate deficiency
4. Farrell CL et al., 2013 – Serum vs Red Cell Folate

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