When a blood specimen is described as “hemolyzed,” it means the red blood cells within the collected sample have broken open. This process, called hemolysis, releases their internal contents into the surrounding plasma or serum. Hemolysis alters the sample itself, not necessarily reflecting a patient’s health condition. This issue impacts the reliability of laboratory test results, often requiring a new blood draw for accurate assessment.
What Hemolysis Is
Hemolysis is the physical rupture of red blood cells, releasing their hemoglobin and other internal components into the plasma or serum. Hemoglobin, the protein responsible for blood’s red color, changes the sample’s appearance upon release. Instead of the typical clear, straw-yellow color, a hemolyzed sample appears pink, red, or even cherry-red, depending on the extent of hemolysis. This discoloration indicates the sample’s integrity is compromised, and free hemoglobin can interfere with laboratory analyses.
Why Hemolysis Occurs
Most instances of hemolysis in blood samples are not due to a patient’s medical condition but rather to factors related to the collection, handling, or processing of the sample. Improper venipuncture technique is a common contributor, such as using a needle that is too small, which can cause red blood cells to break as they are forced through a narrow opening. Drawing blood too forcefully, either with a syringe or through an intravenous catheter, can also damage these fragile cells. Vigorous shaking of the blood collection tube instead of gentle inversion can mechanically disrupt red blood cells. Delays in processing, extreme temperatures during transport or storage, and incomplete filling of collection tubes can also lead to hemolysis.
How Hemolysis Affects Lab Results
Hemolysis significantly impacts the accuracy of laboratory test results because contents released from broken red blood cells interfere with many analytical methods. Red blood cells contain high concentrations of substances like potassium, lactate dehydrogenase (LDH), and aspartate aminotransferase (AST). When released into plasma or serum, these can falsely elevate test results for specific analytes, potentially leading to misinterpretation. For instance, a hemolyzed sample might show an artificially high potassium level, prompting unnecessary medical interventions.
Free hemoglobin itself can interfere with tests relying on light absorption, a common method in clinical chemistry. This optical interference leads to inaccurate readings for various tests, including some liver function tests and immunoassay measurements. Hemoglobin can also chemically interfere with assay reactions or degrade other analytes, such as insulin, causing falsely decreased results. Such inaccuracies can lead to incorrect diagnoses or inappropriate treatment decisions, which is why laboratories often reject hemolyzed specimens.
What Happens After a Hemolyzed Specimen
When a laboratory receives a hemolyzed blood specimen, it typically cannot be reliably processed for many tests. Laboratories often use automated systems to detect hemolysis, or it may be visually apparent from the pink or red discoloration of the plasma or serum. Upon identifying a hemolyzed sample, the laboratory usually notifies the healthcare provider who ordered the tests.
The most common next step is to request a redraw of the blood sample. This ensures a new, high-quality specimen is obtained for accurate and reliable test results. While a redraw can be inconvenient, it is a routine measure for patient safety and proper medical management. A hemolyzed sample usually signifies an issue with sample collection or handling, rather than an underlying health problem for the patient.