Abstract
We encountered the case of a patient with IgM type monoclonal gammopathy whose IgM value was measured to be falsely low without notification by an error code using a turbidimetric immunoassay (TIA) system. Although the true IgM value might be about 2,800 mg/dL as indicated by protein fraction electrophoresis, the value was 420 mg/dL in the original assay. Assay by sample dilution was carried out, but the values remained low up to 10-fold dilution. The reaction curve suggested that the generation of abnormal turbidity in the first reaction at a low dilution was responsible for the problem. No error code appeared in any dilution series of the patient’s serum. Measurements of IgG and IgA were also affected and the values were falsely low. Given that we reported the case of another patient with IgM monoclonal gammopathy whose IgM was falsely low as determined by TIA, we strongly recommend to suspect a false result and conduct further tests to collect information, such as the albumin-to-globulin ratio, or protein fraction electrophoresis in IgM monoclonal gammopathy. Regarding the TIA system, the construction of a retest logic, improvement of reagents, and installation of an abnormal reaction detection mechanism are necessary.
