Search

In a recent publication in this journal (1), the mechanisms, detection and prevention of gammopathy interference in clinical chemistry assays were discussed. Here, we report a case in which a monoclonal gammopathy was detected by measurement of the semi-quantitative serum indices on a MODULAR ANALYTICS P module (Roche Diagnostics, Mannheim, Germany). For the serum index measurement, 8 mL of sample are mixed with 200 mL of saline and absorbances at 480, 505, 570, 600, 660 and 700 nm are measured. From these absorbance values, semi-quantitative results are calculated for the degree of lipemia, hemolysis and icterus present in the sample. The degree of lipemia can be more precisely described as the degree of turbidity in the sample. The lipemia index is equivalent to the concentration of Intralipid , up to a linearity limit of 1000 mg/dL. A 50-year-old female patient was admitted to hospital for loss of consciousness, subsequent collapse

Monoclonal gammopathy is characterized by the presence of an M-protein in serum or urine that has homogeneous structural and functional properties. It can occur in very high concentrations and may cause significant interference in clinical chemistry assays. Examples of gammopathy interference for the analytes glucose, bilirubin, gamma-glutamyltransferase, urea and ferritin are presented. Various mechanisms of interference are described, such as the production of turbidity by the M-protein and the binding of the M-protein to a component of the test system or analyte. In immunoglobulin tests, the M-protein is the analyte itself and may not be completely bound by the test antibody owing to its structural properties. Modern analyzers can detect unusual changes in absorption during the course of a reaction, and thus the formation of turbidity due to M-proteins. This interference may be prevented by optimizing the buffering conditions of the reagents to avoid the formation of turbidity or by removal of the M-protein prior to analysis of the sample. Owing to the unique properties of each M-protein, it is impossible to protect common clinical chemistry test systems completely from gammopathy interference. Therefore, efficient ways for the detection of such interference are needed.