Falsely elevated plasma creatinine due to monoclonal gammopathy Analytical interference may give rise to falsely elevated as well as reduced clinical biochemical results. Hemolysis, icterus and lipemia in patient samples are well-known causes of analytical interference. Laboratories usually automatically check for these interferences and take them into account. However, other causes of interference are more difficult to detect, such as those caused by heterophilic antibodies and in this case a falsely elevated plasma creatinine level caused by a monoclonal IgM gammopathy. Analytical interference should be considered in cases with unexpected laboratory results and inconsistent pattern of results, in which contact and discussion with the laboratory is advised.