Pitfalls in the determination of common analytes in the critically ill.

In the critically ill, the pre-analytical aspects of blood gas analysis still require attention from the clinician. Sampling and transport remain critical factors. Use of drugs may create analytical interferences for common analytes like glucose and protein. Icterus may falsely reduce creatinine and albumin values. Changes in the serum or plasma matrix (reduction of protein, increased covolume of solutes, ...) may furthermore cause important effects on the distribution of electrolytes. Enzyme activity measurements may be erroneous due to lack of essential oligoelements or reducing substances. Immunoassays may suffer from interferences caused by auto-antibodies. In case of hemolysis, a careful interpretation of test results is mandatory.