Hemolyzed Samples and Laboratory Interference
A hemolyzed sample does NOT cause falsely elevated sodium or BUN levels; in fact, hemolysis has minimal to no clinically significant effect on these specific analytes. Both sodium and BUN measurements remain within acceptable error limits even with moderate to severe hemolysis 1.
Effect of Hemolysis on Sodium
Sodium measurements are remarkably stable in hemolyzed samples, with mean differences between hemolyzed and non-hemolyzed samples remaining within Clinical Laboratory Improvement Amendments (CLIA'88) total allowable error limits across all degrees of hemolysis 2, 1.
The percentage difference for sodium in hemolyzed samples compared to fresh samples stays within acceptable criteria, making it safe to analyze sodium even in visibly hemolyzed specimens 1.
Effect of Hemolysis on BUN
BUN is one of the most hemolysis-resistant analytes, with all dilutions of hemolyzed samples (from 10% to 100% hemolysis) showing percentage differences within total allowable error limits 1.
Studies consistently demonstrate that BUN measurements remain accurate and clinically reliable regardless of hemolysis severity 2, 1.
It is safe to analyze a hemolyzed sample for BUN without requiring sample rejection or redraw 1.
Analytes Actually Affected by Hemolysis
The following analytes ARE significantly affected by hemolysis and should NOT be analyzed in hemolyzed samples:
Potassium (K+): Shows marked elevation due to release from lysed red blood cells, exceeding acceptable error limits even with mild hemolysis 2, 1.
Lactate dehydrogenase (LDH): Dramatically elevated due to high intracellular RBC concentrations 2, 1.
Aspartate aminotransferase (AST): Significantly increased with hemolysis 2.
Total protein: Exceeds acceptable limits in hemolyzed samples 2, 1.
Phosphorus: Shows clinically significant elevation with hemolysis 2, 1.
Clinical Interpretation in Your Patient
Given that your patient has:
- Normal creatinine and GFR
- Elevated sodium and BUN
- A hemolyzed sample
The elevated sodium and BUN are NOT artifacts of hemolysis and represent true physiological values 2, 1. You should investigate other causes:
Causes of Elevated BUN with Normal Creatinine
Volume depletion/prerenal azotemia: Enhanced tubular reabsorption of urea occurs with decreased renal perfusion while creatinine clearance remains relatively stable 3.
High protein intake or increased protein catabolism: BUN rises disproportionately to creatinine 3.
Gastrointestinal bleeding: Absorbed blood proteins increase BUN 3.
Medications: Corticosteroids, tetracyclines can increase BUN 3.
Causes of Elevated Sodium with Normal Renal Function
Dehydration/water deficit: Pure water loss concentrates sodium 4.
Diabetes insipidus: Central or nephrogenic causes 4.
Hyperaldosteronism: Sodium retention with normal GFR 4.
Laboratory Quality Considerations
Good laboratory practices should routinely detect hemolysis through hemolytic index measurement and prevent release of erroneous results for affected analytes 5.
Creatinine measurement can be affected by hemolysis through enzymatic interference, but this typically causes falsely LOW values, not elevation 5.
Request repeat testing only for potassium, LDH, AST, total protein, and phosphorus if clinical decisions depend on these values 2, 1.