Streptococcal Glomerulonephritis is best diagnosed by

In rheumatic fever and glomerulonephritis, the retrospective diagnosis of streptococcal infection may be established by demonstrating a high level of antibody to streptococcal toxins. Antideoxyribonuclease B titers higher than 300 are taken as significant. It is useful in the retrospective diagnosis of streptococcal pyoderma, in which ASO titer is of much less value. Reference: Textbook of Microbiology; Anathanarayan and paniker's; 10th edition; Page no: 214