FACTORS OF INTERFERENCE IN LABORATORY INVESTIGATIONS: HEMOLYSIS, ICTERUS, LIPEMIA

Abstract

The accuracy of laboratory investigation results depends on various factors, including interfer- ence factors. Additionally, it is worth noting that a significant number of samples are photometrical- ly measured in the wavelength range of 350 to 600 nm, which corresponds to the absorption peak of many interferents. In laboratories where the process of sample rejection is established based on serum indices (color scale) and specific cutoff points for samples showing hemolysis, icterus, and lipemia, the issuance of falsely elevated/decreased investigation results to the clinic is avoided. The declared criteria for sample rejection should comply with the recommendations of CLSI CA-56A and CLSI EP 07 standards. The majority of errors in the preanalytical stage are caused by hemolysis. All hemolyzed sam- ples with a concentration of free hemoglobin equal to or greater than 10.0 g/L should be rejected, and the laboratory report should indicate the reason for rejection as "Hemolyzed sample. Resampling is required." Each laboratory establishes its own cutoff point for free hemoglobin, bili- rubin and triglicerol concentration in the sample. This is because an increase in hemolysis index in serum/plasma leads to falsely increased levels of certain analytes (such as inorganic phosphorus, potassium, folic acid, magnesium, iron, urea, LDH, AST, ALT). Conversely, the concentration of albumin, bilirubin, glucose, sodium, and chloride in such samples is falsely decreased. The presence of icterus in samples is always indicative of a pathological process. The elevation of bilirubin con- centration in the sample will be reflected in the increase/decrease of analytes such as creatinine, total protein, triglycerides, cholesterol, phosphorus, magnesium, urea, hormones (free triiodothyro-nine, testosterone, estradiol), and others. An increase in triglyceride and lipoprotein concentration in the sample significantly affects the levels of analytes such as phosphorus, creatinine, total protein and calcium. The presence of hemolysis, icterus, and lipemia in samples affects the measurement of various analytes and, consequently, the results of laboratory investigations and patient safety. Laboratories should have a developed procedure for systematic identification of interfering agents and decision- making regarding the handling of such samples to ensure the reliability of obtained data.