The range of antistreptolysin-O titer among 3129 healthy individuals in winter and summer in Tehran, Iran.

A rise in ASO titre can be demonstrated in 75-80% of patients following untreated streptococcal upper respiratory infection. The difficulty, however, is that there is no such thing as normal ASO titre. The levels encountered in a given population depend upon age, geographical location, season, etc. It was, therefore, on this basis that sera were taken from 3129 healthy individuals during winter and summer in Tehran for the determination of ASO titres. Sixty-three individuals were treated both during summer and winter. During summer only 4 (6%) had titres above 250 T.U. and 59 (94%) below 250 T.U. The same individuals, when tested during the winter, showed that 7 (11%) had ASO titres above 250 T.U. and 56 (89%) below 250 T.U. This seasonal difference is statistically significant. In another study 320 individuals were tested during summer and another 394 individuals during winter. Among the summer group 31 (10%) were above 250 T.U. and 289 (90%) were below 250 T.U. In the winter group 55 (14%) were above 250 T.U. and 339 (86%) were below 250 T.U. This difference is again statistically significant. Further, 35 samples of pooled sera representing 2289 individuals were treated during the winter. Here 563 (24%) were above and 1723 (76%) were below 250 T.U. The possible sources of error in this group, in comparison with the other, are discussed.