Interfering substances in test results of clinical samples

In the testing of clinical samples, it is sometimes encountered that there are no abnormalities in reagents, instruments and operations, and the results of quality control and other samples are normal, but the measured values of individual samples are inconsistent with clinical judgment. This situation may be the cause of interfering substances. In recent years, the influence of interfering substances on the results of clinical chemistry tests has received more and more attention.

Interfering substances in test results of clinical samples

Classification of interfering substances


Metabolites of the patient's pathology, such as abnormal monoclonal immunoglobulin in patients with multiple myeloma.


Drugs used in the treatment of patients, such as ascorbic acid, calcium hydroxybenzenesulfonate, dobutamine hydrochloride and so on.


Substances ingested by the patient, such as alcohol, nutrients, and beverages.


Additives during sample processing, such as anticoagulants, preservatives, stabilizers, and so on.


Contaminants introduced by the operator during sample processing, such as hand cream, glove dust, etc.


Endogenous interfering substances in the sample matrix itself, such as bilirubin, hemoglobin, triglycerides, cholesterol, etc.

Interfering substances in test results of clinical samples

Mechanisms by which interfering substances interfere with the immune response

1.Physical effects

interfering substances have similar physical properties with analytes, such as color, light scattering (light absorption), electrode response, elution sites.

2.Chemical effects

interfering substances can compete for reagents, inhibit the indication reaction, change the morphology of the analyte.

3.Enzyme inhibition

interfering substances can chelate metal ions necessary for enzyme activation, bind enzyme catalytic sites, oxidize sulfhydryl groups necessary for enzyme molecules, and so on.


interfering substances can react with reagents in the same way as analytes, and it can cross-react with antibodies in immunochemical methods.

5.Water substitution

Water-soluble substances (proteins, lipids) in the sample affect the determination of analytes by substituting the volume of water-soluble plasma.

6.Matrix effect

interfering substances can change the physical properties of the sample matrix, such as viscosity, surface tension, ionic strength, etc.

Methods of avoiding or minimizing interference

 Sample dilution. If there is interference, the sample dilution is not linear, to be measured when the sample value becomes linear, that is, the measured value is accurate.

 Pay attention to the standardization of sample handling:Keep blood collection instruments(including syringes, needles, and test tubes)clean;Syringe needles should not be sterilized with alcohol, as alcohol can cause hemolysis;The pressure pulse band should not be tied too tightly for too long, and the blood should not be injected into the test tube too quickly when drawing blood, but slowly injected into the test tube along the wall of the tube, so as not to cause rupture of blood cells due to excessive blood bubbles;Blood should not be stored in the refrigerator freezer to avoid hemolysis caused by melting. Blood should not be left for too long to prevent disinfectant or other substances from dripping into the specimen.

 Pay attention to the status of the sample. When there is abnormality mark it on the report or ask for re-collection of blood.

 Check drug instructions in advance and, if possible, stop taking medication some time before blood collection.

 Enhance the anti-interference ability of in vitro diagnostic reagents by improving the process.

 Change the test method.

Interfering substances in test results of clinical samples






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