Jinny's graph shows that bilirubin interference has a more pronounced effect at lower concentrations of creatinine. However at higher concentrations this is fairly constant. Depending on the level of bilirubin in the patient sample, diluting the sample might not completely resolve the problem at low concentrations. So although performing a dilution on the patient sample might be a possible solution when measuring creatinine in icteric samples, it all depends on the magnitude of the dilution and the initial bilirubin level. This means that a higher dilution might be required to resolve the problem of bilirubin interference, however this may come at the expense of lowering the concentration of creatinine so much that its concentration falls below the assay's detection limit.
I am of the opinion that when dealing with icteric samples one has to keep in mind that this is not a type of interference which one can avoid by for example using proper sample collection or handling (example to avoid haemolysis), it is the patients clinical condition which is causing this situation. So I think that we should not be telling the patient "I cannot give you a creatinine level because you have liver failure and you have a high bilirubin!" The same applies to other chemistry parameters which are affected from icterus. We should try to find a suitable way on how to handle such situations so to be able to provide our patients with the reliable diagnostic values which are needed for treating their condition. I agree with David that this issue requires further investigation.
Best Wishes to All,
Ian
Ian Brincat
Allied Health Practitioner Medical Laboratory Scientist
Paediatric Medicine Laboratory
Clinical Chemistry
Department of Pathology
Mater Dei Hospital
t: +356 25456368 25456377 e: [log in to unmask] | www.gov.mt
Ministry for Health
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