The influence of bilirubin, haemolysis and turbidity on 20 analytical tests performed on automatic analysers. Results of an interlaboratory study.

The director of a laboratory has to be sure to give out reliable results for routine tests on automatic analysers regardless of the clinical context. However, he may find hyperbilirubinaemia in some circumstances, parenteral nutrition causing turbidity in others, and haemolysis occurring if sampling is difficult. For this reason, the Commission for Instrumentation of the Société Française de Biologie Clinique (SFBC) (president Alain Feuillu) decided to look into "visible" interferences--bilirubin, haemolysis and turbidity--and their effect on 20 major tests: 13 substrates/chemistries: albumin, calcium, cholesterol, creatinine, glucose, iron, magnesium, phosphorus, total bilirubin, total proteins, triacylglycerols, uric acid, urea, and 7 enzymatic activities: alkaline phosphatase, alanine aminotransferase, alpha-amylase, aspartate aminotransferase, creatine kinase, gamma-glutamyl transferase and lactate dehydrogenase measured on 15 automatic analysers representative of those found on the French market (Astra 8, AU 510, AU 5010, AU 5000, Chem 1, CX 7, Dax 72, Dimension, Ektachem, Hitachi 717, Hitachi 737, Hitachi 747, Monarch, Open 30, Paramax, Wako 30 R) and to see how much they affect the accuracy of results under routine conditions in the laboratory. The study was carried out following the SFBC protocol for the validation of techniques using spiked plasma pools with bilirubin, ditauro-bilirubin, haemoglobin (from haemolysate) and Intralipid (turbidity). Overall, the following results were obtained: haemolysis affects tests the most often (34.5% of cases); total bilirubin interferes in 21.7% of cases; direct bilirubin and turbidity seem to interfere less at around 17%. The different tests are not affected to the same extent; enzyme activity is hardly affected at all; on the other hand certain major tests are extremely sensitive, increasingly so as we go through the following: creatinine (interference of bilirubin), triacylglycerols (interference of bilirubin and haemoglobin), glucose (interference of bilirubin), cholesterol (interference of bilirubin), phosphorus (interference of bilirubin and haemoglobin), uric acid (interference of turbidity), iron (interference of haemoglobin and turbidity), total proteins (interference of bilirubin, haemoglobin and turbidity) and bilirubin (interference of haemoglobin and turbidity). Three categories of interferences can be found: interference by addition, chemical interference and spectral interference, and the results show that not only the choice of a method is important on the analyser, but also how this has been adapted. By looking into these conditions carefully, it is sometimes possible to find a reason for the problem and thereby a simple solution to correct it.(ABSTRACT TRUNCATED AT 400 WORDS)