HEMÓLISIS de muestras: Causas y recomendaciones

Understanding Hemolysis in Clinical Laboratories

What is Hemolysis?

• Hemolysis refers to the breakdown of blood cells, releasing their contents into serum or plasma, characterized by shades from pink to intense red.

• It is quantitatively defined as free hemoglobin levels exceeding 0.3 g/L and is a common preanalytical error leading to sample rejection.

Impact of Hemolysis on Analytes

• Hemolysis can cause fictitious increases in analyte levels, particularly potassium due to its higher intracellular concentration compared to extracellular.

• Enzymes like lactic dehydrogenase, aspartate aminotransferase, and creatine phosphokinase are also significantly affected by hemolysis.

• The color change from hemoglobin interferes with bilirubin measurements and other colorimetric techniques that absorb at similar wavelengths.

Types of Hemolysis

In Vivo vs. In Vitro

• In vivo hemolysis occurs in about 2% of cases due to conditions like hemolytic anemias or autoimmune diseases; it cannot be prevented by phlebotomists.

• In vitro hemolysis accounts for 98% of cases and can be prevented through proper phlebotomy and sample handling practices.

Causes and Prevention of In Vitro Hemolysis

Preanalytical Phase Considerations

• One major cause is inadequate drying of the skin after alcohol swabbing, which can contaminate samples if not dried properly.

• Excessive manipulation during vein puncture can damage tissues and lead to hemolyzed samples; knowing vein direction helps minimize this risk.

Sample Handling Techniques

• Blood should not be transferred directly from a syringe into tubes by puncturing the cap; alternative collection methods should be used to avoid negative pressure that causes hemolysis.

Storage and Transportation Issues

• Samples stored outside optimal temperatures (2° - 6° C), especially extreme heat or cold, accelerate cell death leading to hemolysis.

• Using conventional red tubes without separating gel may result in delayed detection of hemolysis days after extraction due to natural cell death processes.

Transporting Samples Safely

Understanding Hemolysis in Laboratory Samples

Transporting Serum to Avoid Cell Contact

• The ideal practice is to transport serum that has been separated from the globular package to prevent contact with cells, which can lead to glucose consumption by those cells.

• There are scenarios where obtaining a new sample is challenging due to the patient's condition or if they are no longer present in the laboratory or hospital when hemolysis is observed.

• Laboratory procedures may vary significantly as there is no standardized protocol for handling hemolyzed samples.

Approaches to Handling Hemolyzed Samples

• When faced with a hemolyzed sample, one option is to reject it entirely and refrain from processing or reporting any parameters affected by hemolysis.

• An alternative approach involves processing and reporting the sample while noting its hemolyzed state and degree of hemolysis, including free hemoglobin concentration for physician consideration.

• Many laboratories do not adopt this latter approach since critical values like potassium and lactic dehydrogenase become meaningless when evaluated in a hemolyzed sample.

Recent Evaluations on Sample Processing