Formation of nonspecific precipitants in sera by counterimmunoelectrophoresis.

Formation of nonspecific precipitants in sera in different kinds of agarose and batches of barbital buffer by routine counterimmunoelectrophoresis was observed. These nonspecific precipitants consistently locating at the cathodal side of the well upon counterimmunoelectrophoresis can lead to the incorrect interpretation that a specific antibody is present in the patient's serum against the antigens tested. This observation indicates the importance of including a negative control (patient's serum alone) with each individual sample tested by counterimmunoelectrophoresis for the detection of specific antibody to reduce false-positives.