During the past few years the congo red test for the confirmation of amyloid deposits in the body has been serviceable in our hands in elucidating the nature of obscure enlargements of the spleen and the liver. Since this test is not as well known as it deserves to be, and since we feel that many problems in diagnosis might be clarified by its use, reports are presented of 7 cases in which this test was of great value in arriving at a diagnosis. It should be emphasized that if positive, the information derived from the test is unequivocal, but there may be a small to moderate degree of amyloid present, undetectable by the test.
Bennhold1 found that congo red, if carefully prepared, could be injected intravenously without danger. He presented 10 cases demonstrating that amyloid deposits in the liver would remove the dye rapidly from the circulating blood.
HARMON PH, KERNWEIN G. UTILITY OF THE CONGO RED TEST IN DIAGNOSIS AND IN DIFFERENTIAL DIAGNOSIS. Arch Intern Med (Chic). 1942;70(3):421-433. doi:10.1001/archinte.1942.00200210076006