What is the appropriate management for a patient with low hematocrit (Hct) and red blood cell (RBC) count but normal hemoglobin (Hb) levels?

Laboratory Artifact: Verify Accuracy Before Clinical Action

The finding of low hematocrit and low RBC count with normal hemoglobin is physiologically inconsistent and most likely represents a laboratory error or pre-analytical artifact that requires immediate sample verification before any clinical intervention.

Understanding the Discrepancy

The relationship between hemoglobin (Hb), hematocrit (Hct), and RBC count follows predictable mathematical relationships in clinical practice:

• Hematocrit typically equals approximately 3 times the hemoglobin value (Hct% ≈ 3 × Hb g/dL), though this relationship can vary with age and is not perfectly linear 1, 2
• When hemoglobin is normal, both hematocrit and RBC count should also be within normal ranges in the absence of specific rare conditions 1
• The combination you describe violates basic hematologic principles and suggests measurement error rather than true pathology 3

Immediate Action Steps

1. Repeat the Complete Blood Count Immediately

• Redraw a fresh blood sample using proper technique to eliminate pre-analytical variables 3
• Ensure proper anticoagulant (K3EDTA) and mixing of the sample, as inadequate mixing can cause spurious results 3
• Verify sample was analyzed within appropriate timeframe (ideally within 4-6 hours of collection at room temperature or 24 hours if refrigerated at 4°C) 3
• Review the peripheral blood smear to assess RBC morphology and verify automated counter results 4

2. Consider Pre-Analytical Factors

Common causes of discordant results include:

• Clotted sample causing falsely low RBC and Hct with preserved Hb measurement 3
• Improper sample storage or transportation affecting RBC integrity while hemoglobin remains stable 3
• Instrument malfunction or calibration error in the automated cell counter 3
• Hemolysis can affect measurements differently depending on timing and severity 3

If Results Persist After Verification

Should the discrepancy remain after proper sample collection and analysis:

Investigate Rare Causes

• Evaluate for plasma volume abnormalities that could theoretically affect Hct disproportionately 2
• Consider polycythemia vera workup if Hb is at upper normal range, as Hct targets differ (maintain <45% in PV patients regardless of Hb) 4
• Assess for occult blood loss with serial measurements, as initial Hb may not reflect acute hemorrhage 4
• Check iron studies, B12, and folate to identify correctable causes before attributing to artifact 4

Clinical Context Matters

• In hemodynamically stable patients without symptoms, observation with repeat testing in 24-48 hours is appropriate 4
• If patient is symptomatic (tachycardia, tachypnea, postural hypotension) with Hb <10 g/dL, transfusion threshold is 8-10 g/dL regardless of Hct discrepancy 4
• For patients with cardiovascular disease, use transfusion trigger of 8 g/dL (target 10 g/dL) if true anemia is confirmed 4, 5

Key Pitfalls to Avoid

• Do not initiate treatment based on discordant laboratory values without verification - this represents a critical safety issue 3
• Do not assume the automated counter is always correct - peripheral smear review by experienced personnel is essential when values don't correlate 4
• Do not delay urgent care if patient is hemodynamically unstable - treat the patient clinically while investigating the laboratory discrepancy 4, 5