Interferences on Serum samples and it preservation. Compiled by: Thamer Hamdan M.Sc. Clinical Microbiology and Immunology. Interference occurs when a substance or process falsely alters an assay result. Interferences are classified as endogenous or exogenous.
Compiled by: ThamerHamdan
M.Sc. Clinical Microbiology and Immunology
Interference occurs when a substance or process falsely alters an assay result.
Endogenous interference originates from substances found naturally in the patient sample. They may be natural substances or health-related factors:
-haemolysis (haemoglobin and other substances) (reddish).
-bilirubin (Icteric) (yellowish).
-Lipids, proteins, antibodies (autoantibodies, heterophile antibodies).
-excessive analyte concentration, and cross-reacting substances.
Exogenous interference results from substances not naturally found in the patient’s specimen including
-Drugs (parent drug, metabolites, and additives),
- poisons, herbal products, IV fluids, substances used as therapy.
- It may also arise from collection tube components, test sample additives such as preservatives.
-Processes affecting the sample (e.g. transport, storage, and centrifugation).
-Clots (post-refrigeration in heparin plasma, slow-clotting serum).
- Carryover contamination.
Hemolysis is the breakage of the red blood cell’s (RBC’s) membrane, causing the release of the hemoglobin and other internal components into the surrounding fluid. Hemolysis is visually detected by showing a pink to red tinge in serum or plasma.
• Vigorous mixing or shaking of a specimen may cause hemolysis.
• Not allowing the serum specimen to clot for the recommended amount of time can result in fibrin formation in the serum. The use of applicator sticks to dislodge the fibrin may cause rupture of RBCs, resulting in hemolysis.
• Prolonged contact of serum or plasma with cells may result in hemolysis.
• Exposure to excessive heat or cold can cause RBC rupture and hemolysis.
Effects of hemolysis
-for short term storage: refrigerator
-for long term storage: Freezer or deep freeze