Confirming Lipemic, Icteric, or Hemolyzed Plasma
The most accurate method to confirm lipemic, icteric, or hemolyzed plasma is by observing plasma color after performing a microhematocrit (option A). 1
Understanding Plasma Appearance and Interferences
Plasma normally appears as a clear, transparent yellow fluid. However, various conditions can alter its appearance:
- Hemolyzed plasma: Appears orange or red due to disruption of red blood cell membranes and release of hemoglobin
- Lipemic plasma: Appears milky or opaque due to elevated lipoproteins (often in postprandial state)
- Icteric plasma: Shows intensified yellow coloration due to elevated bilirubin 1
Why Microhematocrit Is the Correct Method
The microhematocrit procedure allows direct visual observation of separated plasma after centrifugation, making it possible to clearly identify:
- The color and transparency of the plasma layer
- The presence of hemolysis (reddish discoloration)
- Lipemia (milky appearance)
- Icterus (intense yellow coloration) 1
Why Other Options Are Incorrect
Option B (Evaluation of MCV, RBC, and Hct): These parameters measure red blood cell characteristics but do not directly assess plasma appearance or the presence of interferences.
Option C (Manual blood smear review): While useful for cellular evaluation, blood smears don't allow assessment of plasma characteristics since the plasma is spread thinly and dried during preparation.
Option D (Calculations using Hgb and Hct): These calculations relate to red cell indices but don't provide information about plasma appearance or interferences.
Clinical Importance of Detecting Interferences
Identifying these interferences is critical because:
- Hemolyzed, icteric, or lipemic samples can lead to inaccurate laboratory results and potential medical errors 2
- These interferences can affect multiple assays through various mechanisms:
- Spectrophotometric interference
- Release of intracellular components
- Sample dilution
- Chemical interference 3
Modern Laboratory Practices
While visual inspection through microhematocrit is the traditional method to confirm these interferences, modern laboratories increasingly use automated detection systems:
- Automated spectrophotometric detection (serum indices) provides more standardized and objective assessment 2
- Visual inspection has been shown to be highly subjective with poor inter-observer agreement (weighted kappa coefficients: 0.555 for lipemia, 0.529 for icterus, and 0.638 for hemolysis) 2
Pitfalls and Caveats
- Visual assessment is subjective and varies between observers, with the lowest agreement typically seen in assessing icterus 2
- Different assays have varying sensitivities to these interferences; coagulation assays are particularly vulnerable to hemolysis 4
- The degree of interference depends on both the level of the interferent and the specific assay methodology 5
For optimal laboratory practice, microhematocrit observation should be supplemented with automated detection systems whenever possible to ensure accurate identification of these common preanalytical interferences.