Use and interpretation of the antistreptolysin test.

Numerous laboratory tests have been devised and used with varying enthusiasm as aids in the diagnosis of rheumatic fever, but the establishment of the intimate relationship between this condition and upper respiratory tract streptococcal infection has directed interest mainly to the demonstration of serological evidence of streptococcal activity in rheumatic subjects. Of the various tests used for this purpose, the antistreptolysin "O", originally introduced by Todd (1932a, b), has emerged as the most reliable and consistent, but as yet there is no general agreement as to its true value, possibly due to lack of understanding of its interpretation and limitations. In this laboratory the estimation of antistreptolysin "O" titres (A.S.L.T.) was undertaken, in the first place, as part of a study on rheumatic heart disease in conjunction with the late area cardiologist, Dr. J. W. Brown. However, it rapidly became established in the area as a routine test in the investigation of acute rheumatism and other diverse clinical conditions. The experience gained from the interpretations of