Impact of Lipemic Plasma on CBC Parameters
Hemoglobin measurement is the directly measured parameter most significantly affected by lipemic plasma on most automated CBC instruments. 1, 2
Mechanism of Interference
Lipemic plasma affects automated CBC analysis through several mechanisms:
- Lipemic samples appear milky or opaque due to elevated lipoproteins, creating optical interference 1
- The turbidity caused by high triglyceride levels directly interferes with spectrophotometric measurements 2
- This interference primarily affects hemoglobin measurement, which relies on direct colorimetric assessment 3, 2
Specific Parameters Affected
Primary Impact:
- Hemoglobin (Hgb): Most significantly affected parameter
Secondary Impacts:
- Mean Corpuscular Hemoglobin Concentration (MCHC): Affected due to its calculation using hemoglobin values 2
- Mean Corpuscular Hemoglobin (MCH): Also affected as it's calculated using hemoglobin values 2
Detection of Lipemic Interference
Lipemic plasma can be identified through:
- Visual inspection - appears milky or opaque 1
- Microhematocrit procedure - allows direct observation of separated plasma after centrifugation 1
- Automated lipemia index on some analyzers
Correction Methods
When lipemic samples are encountered:
- High-speed centrifugation (10,000×g for 15 minutes) can effectively remove lipemia without significantly affecting test results 4, 5
- A correction formula can be applied using separate measurements of plasma and whole blood 2:
- Measure hemoglobin in both whole blood and separated plasma
- Calculate corrected hemoglobin by subtracting the plasma contribution
Clinical Implications
- Uncorrected lipemic interference can lead to:
- Misdiagnosis of anemia or polycythemia
- Inappropriate treatment decisions based on inaccurate hemoglobin values
- Errors in calculated parameters like MCHC and MCH
Practical Recommendations
- Always visually inspect samples for lipemia before analysis
- Consider high-speed centrifugation for lipemic samples
- Document the presence of lipemia in laboratory reports
- Consider requesting a new sample collected after fasting when severe lipemia is present
- Apply correction formulas when available for critical hemoglobin measurements in lipemic samples
Common Pitfalls
- Failing to recognize lipemia as a source of analytical error
- Reporting potentially inaccurate hemoglobin results without appropriate correction
- Using ultracentrifugation (which is effective but impractical in most clinical settings) when high-speed centrifugation is sufficient 4
- Applying liquid-liquid extraction methods that may introduce additional interferences 4
Understanding the significant impact of lipemia on hemoglobin measurement is essential for accurate CBC interpretation and appropriate clinical decision-making.