The Antistreptolysin O (ASO) titre measures antibodies against streptolysin O, produced by group A streptococcus bacteria. Indicators of illness such as bacterial endocarditis, glomerulonephritis, rheumatic fever, and strep throat. The test aids in evaluating the immune response to untreated streptococcal infections, providing valuable insights for healthcare professionals linking symptoms to prior streptococcal exposure.