The test is a sensitive test for recent streptococcal infection. A rise in ASO begins about one week after infection and peaks two to four weeks later. ASO levels do not rise with cutaneous infections. In the absense of complications or reinfection, the ASO level will fall to preinfection levels within 6 to 12 months. Over 80% of patients with acute rheumatic fever and 95% of patients with acute glomerulonephritis have elevated levels of ASO.