Study of the Disappearance of Congo Red from the Blood of Non-amyloid Subjects and Patients

In a case suspected clinically of having amyloidosis because of the presence of a chronic infection, large liver and spleen, and moderate albuminuria, a Congo Red test done by the current standard method (1) proved to be negative according to present interpretation (60 per cent of the dye was removed from the blood at the end of 60 minutes). A moderate amount of amyloid was, however, shown to be present by biopsy of the liver. For this and other considerations it was decided to review the various methods of carrying out the test and the criteria employed in interpretation. In 1923 Bennhold (2) described a method for the laboratory diagnosis of amyloidosis by the intravenous injection of 10 cc. of a 1 per cent solution of Congo Red.' He regarded the disappearance of more than 60 per cent of the Congo Red at the end of an hour as presumptive evidence of amyloid disease. Subsequent investigators (Friedman and Auerbach [1], Taran and Eckstein [31, Lipstein [4], Auerbach and Stemmerman [5]), modified Bennhold's original method because they found that many falsely positive results were obtained using his criteria. They suggested that at least 90 per cent of the dye be absorbed in an hour before making the diagnosis of amyloidosis. In 1942, Taran and Eckstein (3) found that the 4-minute specimen was frequently too light in color to be relied upon as the standard or 100 per cent specimen. They recommended that a 2minute specimen be taken in addition to the 4minute and 1-hour samples, advising that the 2minute specimen be used as the standard for comparison (100 per cent). They gave 1 cc. of a 1 per cent Congo Red solution for each 10 pounds of body weight. In order to avoid errors due to