Antistreptolysin O titre (ASOT) is a blood test used to detect the presence of antibodies against the streptococcus bacteria. The significance of ASOT testing lies in its ability to diagnose recent streptococcal infections, particularly Group A streptococcus (GAS) infections. It helps identify individuals with a recent streptococcal infection, such as strep throat or scarlet fever, as well as those at risk of developing complications like rheumatic fever or post streptococcal glomerulonephritis. ASOT testing plays a crucial role in guiding appropriate treatment and preventing potential long-term complications associated with streptococcal infections.