Anti-streptolysin (ASO) is one of the markers used for diseases such as rheumatic fever or glomerulenephritis, as those diseases are distinguished by a high increase of the anti-streptolysin title in the asymptomatic period of time which anticipates the start of the disease. In this test the anti-streptolysin antibodies eventually present in the serum agglutinate with latex particles sensitized with O-streptolysis, forming an easily visible agglomerate.