A typical blood sample consists of the fluid portion (plasma or serum) and formed elements, including red blood cells, white blood cells, and platelets. Red blood cells make up about 40% to 45% of total blood volume and carry oxygen throughout the body. When a sample is identified as “hemolyzed,” it means the red blood cells have prematurely broken down or ruptured. This rupture releases the cells’ internal contents into the surrounding fluid, which severely compromises the accuracy of laboratory testing and often necessitates a redraw.
Understanding the Process of Hemolysis
Hemolysis is derived from the Greek words “hemo” (blood) and “lysis” (to break or rupture). Red blood cells are enclosed by a delicate membrane that maintains a precise balance of contents. When this membrane is damaged, the cell’s structure destabilizes, causing it to burst.
The primary content released upon rupture is hemoglobin, the protein that gives blood its red color. Hemoglobin spills into the plasma or serum, visibly tinting the fluid a reddish or pinkish color. The cell also releases high concentrations of internal substances, such as specific enzymes and electrolytes, which directly interferes with the accuracy of many blood tests.
Common Causes of Sample Hemolysis
Hemolysis in a collected sample, known as in vitro hemolysis, is most frequently caused by issues during the collection or handling process. Mechanical stress is a common factor, particularly if the blood is forced through a needle that is too small, damaging the fragile red cell membranes. Drawing blood too quickly, especially with excessive suction, generates high pressure that can also cause the cells to break apart.
Improper handling of the sample after collection is another frequent cause of cell destruction. Vigorously shaking a tube, rather than gently inverting it, causes mechanical trauma. Extreme temperature changes, such as freezing or excessive heat, can destroy the red blood cell membranes by altering their structure. Using an incorrect blood-to-anticoagulant ratio in the collection tube can also lead to red cell rupture.
How Hemolysis Affects Laboratory Results
The integrity of a blood test result depends on the liquid component being free of excessive cellular debris. The release of hemoglobin severely interferes with photometric tests, which rely on light absorption to measure substance concentrations. The intense color of the released hemoglobin skews the light readings, causing color interference and leading to inaccurate results for many analytes.
Hemolysis also causes the false elevation of specific substances highly concentrated inside the red blood cells. Potassium (K+), for example, is approximately 23 times more concentrated inside the cells than in the plasma. When cells rupture, this large amount of potassium floods the surrounding fluid, leading to a falsely high lab result. Similarly, intracellular enzymes like Aspartate Aminotransferase (AST) and Lactate Dehydrogenase (LDH) are released, resulting in artificially elevated levels for these common liver and tissue damage markers.
What Happens When a Sample Is Hemolyzed
When a laboratory receives a noticeably hemolyzed sample, standard protocol dictates that it must be rejected for testing. The compromised integrity makes it impossible to distinguish the patient’s true physiological values from the contamination caused by the ruptured cells. The lab will flag the sample and notify the healthcare provider that the specimen is unsuitable for analysis.
The practical resolution is almost always a recollection, meaning the patient must have their blood drawn again. Healthcare professionals take corrective steps during the second draw to prevent recurrence, such as using a larger needle size or mixing the blood more gently. The goal is to obtain a fresh, non-hemolyzed sample to ensure the patient receives accurate diagnostic information.