Three Extra Helpful Parameters on the Full Blood Count (FBC)

Available Only at Reference Facilities

PATHCHAT Edition No. 19
Please contact your local Ampath pathologist for more information.

Introduction

🔹 Three additional parameters on the FBC can provide valuable diagnostic insights:

1. Immature Granulocyte Count (IG count).
2. Immature Platelet Fraction (IPF count).
3. Platelet-O Count (Optical Platelet Count).

These parameters are available only on specialized Sysmex XE-2100 analysers at reference laboratories.

1. Immature Granulocyte Count (IG Count)

🔹 What is it?

• The IG count measures the presence of immature granulocytes (stab cells, metamyelocytes, and myelocytes) in peripheral blood.
• In non-pregnant adults and neonates, the presence of IGs indicates infection, inflammation, or bone marrow stimulation.

🔹 Clinical Applications:
✅ Early detection of bacterial infections, especially in children.
✅ Identifying bacterial infections in neonates.
✅ Early recognition of sepsis in adults.
✅ Monitoring immunocompromised patients, including:

• Patients in intensive care units (ICUs).
• Chemotherapy patients.
• HIV/AIDS patients.

🔹 Reference Range:

• Normal IG count: 0.5% or 0.03 × 10⁹/L.

📌 Only available at reference laboratories with specialized software.

2. Immature Platelet Fraction (IPF Count)

🔹 What is it?

• The IPF measures the proportion of newly released (reticulated) platelets, which are larger and more reactive than mature platelets.
• Helps distinguish between bone marrow failure (low platelet production) and peripheral platelet destruction (high platelet consumption).

🔹 Clinical Applications:
✅ Assessing platelet recovery after chemotherapy or bone marrow transplant.
✅ Differentiating thrombocytopenia causes:

• Low IPF: Suggests bone marrow suppression (aplastic anaemia, chemotherapy effects).
• High IPF: Suggests increased platelet destruction (immune thrombocytopenic purpura (ITP), thrombotic thrombocytopenic purpura (TTP)).
  ✅ Predicting bleeding risk in thrombocytopenic patients.
  ✅ Monitoring pregnancy complications, including:
• Pre-eclampsia.
• Pregnancy-induced hypertension (PIH).

🔹 Reference Range:

• Normal IPF count: 1.1% – 6.1%.

📌 The IPF count remains stable in EDTA samples for up to 48 hours at room temperature.

3. Platelet-O Count (Optical Platelet Count)

🔹 What is it?

• Traditional automated analysers struggle to accurately count platelets at low levels due to interference from cell fragments and debris.
• The Platelet-O Count uses fluorescent staining and laser-based flow cytometry to accurately count platelets.
• It distinguishes between:
  • Normal platelets.
  • Giant platelets (common in platelet disorders).
  • Platelet fragments (which can cause false high counts in traditional methods).

🔹 Clinical Applications:
✅ Confirming accurate platelet counts, especially at low levels.
✅ Differentiating giant platelets from red cells.
✅ Correcting false platelet counts in samples with debris or clumping.
✅ Monitoring patients with platelet disorders, including:

• Immune thrombocytopenia (ITP).
• Bone marrow disorders.
• Disseminated intravascular coagulation (DIC).

🔹 Important Considerations:

• Falsely low platelet counts may occur due to platelet clumping (caused by faulty venesection or EDTA-dependent antibodies).
• If an unexpectedly low count is detected:
  • A fresh sample should be collected using a different anticoagulant (e.g., citrate tube).
  • Microscopic evaluation is required to confirm true platelet count.

Platelet Clumping & EDTA Sensitivity

🔹 Causes of Falsely Low Platelet Counts:

• Platelet activation due to faulty venesection.
• Antibody-mediated platelet aggregation (EDTA-dependent reaction) → Leads to Platelet Satellitism (platelets adhering to white blood cells).

🔹 How to Confirm a True Low Platelet Count:
✅ Examine a blood smear under a microscope to check for clumping.
✅ If clumping is suspected, repeat platelet count using a citrate tube instead of EDTA.

Key Takeaways for Clinicians

✅ Immature granulocyte count is useful for early infection detection, especially in sepsis and neonates.
✅ Immature platelet fraction helps differentiate between bone marrow failure and increased platelet destruction.
✅ Platelet-O count improves accuracy in low platelet counts and avoids errors due to clumping or debris.
✅ If platelet clumping is suspected, use a citrate tube instead of EDTA for accurate results.

References

1. Briggs C et al. (2000). New quantitative parameters on a recently introduced automated blood cell counter – the XE2100. Clinical Laboratory Haematology, 22, 345–350.
2. Briggs C et al. (2004). Assessment of an immature platelet fraction (IPF) in peripheral thrombocytopaenia. British Journal of Haematology, 126, 93–99.
3. Bruegel M et al. (2004). Reference values for immature granulocytes in healthy blood donors generated on the Sysmex XE-2100 automated Hematology analyser. Sysmex Journal International, 14(1), 5–7.
4. Segal HC et al. (2005). Accuracy of platelet counting haematology analysers in severe thrombocytopaenia and potential impact on blood transfusion. British Journal of Haematology, 128, 520–525.

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