Factitious results in clinical chemistry tests caused by common endogenous interferents.

T otal laboratory processes are comprised of preanalytical, analytical and postanalytical phases. Quality management must be performed in all phases to yield the accuracy and precision of laboratory results. In spite of large evidence of the benefit in implementing a quality program and the improvement of laboratory automation instruments to reduce all defects within the processes, laboratory errors still occur. The majority of errors lie in the preanalytical phase. Plebani et al, reported that the distribution of mistakes was preanalytical in 68.2%, analytical in 13.3%, and postanalytical in 18.5%. The preanalytical phase involves all the various processes before a sample can be measured. Preanalytical factors are parts of patient-related variables (age, sex, diet, stress, medication, etc.), specimen collection (patient identification, venepuncture techniques, specimen volume, types of anticoagulants, etc.), specimen transport, specimen processing and storage. Analytical factors involve methods and instruments used for measuring analytes in the specimen that currently are performed with a highly advanced technology automation system. Finally, postanalytical factors consist of reporting, comprehension and interpretation of laboratory results. Since the laboratory mistakes are principally detected in the preanalytical phase and may lead to further inappropriate investigations or treatments, detection and management of unsuitable specimens including misidentification, quantity or quality issues play an important role in preventing the errors, thereby reducing unjustified increase in costs. The hemolytic, lipemic or icteric samples which can be detected in the preanalytical phase are considered unsuitable for routine clinical chemistry tests due to biological and analytical interferences. Moreover, the presence of paraproteins interfere in many biochemical measurements. Hemolysis, lipemia, bilirubinemia and paraproteinemia are classified as the most common sources among the endogenous interferents. This article reviews the factitious results in clinical chemistry tests caused by hemolysis, lipemia, bilirubinemia and paraproteinemia and the mechanisms of analytical interferences.