🔬 What Happens to Your Blood Test Results When Hemolysis Occurs?
🔬 What Happens to Your Blood Test Results When Hemolysis Occurs?
In clinical laboratories, one of the most common reasons for sample rejection is hemolysis. Many patients hear, “We need to redraw your blood due to hemolysis,” without fully understanding what this means. Hemolysis can significantly distort test results and interfere with accurate clinical interpretation.
This article outlines why hemolysis occurs, how it affects laboratory values, and which parameters increase or decrease when hemolysis is present.
🩸 1. What Is Hemolysis?
Hemolysis refers to the breakdown of red blood cells (RBCs), leading to the release of intracellular components into the serum or plasma.
While minimal hemolysis can naturally occur, excessive hemolysis during blood collection or specimen handling can alter laboratory values so severely that the results become unreliable.
🩸 2. Why Does Hemolysis Occur?
Most hemolysis happens outside the body (in vitro) during venipuncture or laboratory processing.
▶ (1) Causes Related to Blood Collection Technique
- Pulling the syringe plunger too quickly and forcefully
- Using a needle that is too small
- Incorrect needle angle causing vessel wall trauma
- Forcing blood into collection tubes under pressure
- Excessive vacuum pressure of the tube
- Instructing patients to repeatedly clench and relax their fist
▶ (2) Causes During Laboratory Processing
- Vigorous shaking of blood collection tubes
- Incorrect centrifugation speed or duration
- Strong vibration during specimen transport
- Improper storage (excessive heat, freezing, etc.)
▶ (3) In Vivo Hemolysis (less common)
Although uncommon in routine testing, hemolysis can also occur inside the body due to:
- Hemolytic anemia
- Sepsis
- ABO-incompatible transfusion
- G6PD deficiency
In outpatient and health-screening settings, in vitro hemolysis is by far the most frequent cause.
🧪 3. How Hemolysis Affects Laboratory Results
When RBCs rupture, intracellular components flood into serum or plasma, causing certain analytes to rise or fall abnormally.
📈 4. Tests That Increase Due to Hemolysis
These parameters typically increase because of leakage from RBCs or analytical interference.
🔺 (1) Potassium (K⁺)
- One of the most dramatically affected analytes
- RBCs contain high intracellular potassium
- Leading cause of pseudohyperkalemia
🔺 (2) LDH (Lactate Dehydrogenase)
- Extremely high concentration inside RBCs
- Markedly increases even with mild hemolysis
🔺 (3) AST and ALT
- RBCs contain substantial AST and ALT
- AST tends to rise more than ALT
🔺 (4) Iron
- Hemoglobin breakdown releases iron into serum
🔺 (5) Inorganic Phosphate
- Intracellular phosphate leaks into plasma
🔺 (6) Total Protein
- Mild increase due to release of intracellular proteins
🔺 (7) Magnesium, CK
- May also increase depending on degree of hemolysis
📉 5. Tests That Decrease Due to Hemolysis
A few analytes show falsely decreased levels.
🔻 (1) Total Bilirubin
Hemoglobin released from RBCs interferes with photometric bilirubin assays, causing falsely low bilirubin values.
🔻 (2) Others
Certain analytes may appear decreased depending on the measurement method due to optical interference, but bilirubin is the most consistent and clinically relevant.
🧬 6. Why Hemolysis Matters
Excessive hemolysis can lead to:
- Misinterpretation of results
- Unnecessary repeat testing
- False diagnosis, especially hyperkalemia
- Incorrect clinical decisions, potentially dangerous
- Loss of specimen reliability, requiring redraw
Preventing hemolysis during blood collection is essential to ensuring accurate and trustworthy laboratory results.
📚 7. References
- Lippi G, et al. Hemolysis: an overview of the leading cause of unsuitable specimens in clinical laboratories. Clin Chem Lab Med.
- CLSI GP41-A7. Collection of Diagnostic Venous Blood Specimens.
- Simundic AM. Hemolysis interference in clinical chemistry assays: recommendations from the IFCC Working Group.
- Burtis CA, Bruns DE. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics.
- Snyder SR, et al. Impact of hemolysis on clinical laboratory tests. Arch Pathol Lab Med.