Tests for streptolysin-O antibodies in health and suspected streptococcal infections in Saudi Arabia.

'Upper limits of normal' antistreptolysin-O (ASO) titres were determined in various age groups in Saudi Arabia using the conventional haemolysin and the newer, passive agglutination (Blue-ASO) tests. The upper limit of normal values were found to vary with age, being the highest (166 Todd units or 1:320) among the school age children. Serum samples from 744 patients with various clinical manifestations associated with streptococcal infections such as rheumatic fever, glomerulonephritis, tonsillitis, rheumatoid arthritis and polyarthritis were tested by both methods, with the geometric mean titres (GMT) being determined in each age group. In case of school age children with suspected rheumatic fever, and found positive by the tests, a GMT of 458 Todd units (1:1080) was obtained--much higher than the ASO levels detected in positives with glomerulonephritis or tonsillitis. Apart from its relative simplicity, rapidity and ease of performance, the Blue-ASO test was able to detect positivity in 15% of sera from patients of various age groups with suspected rheumatic fever, polyarthritis and tonsillitis who exhibited insignificant levels of ASO by the haemolysin test.