Are you experiencing joint pain, a rash, or other symptoms after a sore throat? This test is essential. The ASO Titre detects antibodies your body makes against 'streptolysin O,' a toxin produced by the Group A Strep bacteria. A positive test doesn't mean you have strep now, but it is powerful evidence of a recent infection. This is crucial for diagnosing post-streptococcal complications like rheumatic fever or glomerulonephritis. This simple blood test provides the 'look-back' evidence your doctor needs to connect your current symptoms to a past infection.