Qualitative Differences between Positive Streptococcal Antifibrinolysin Tests.

Abstract

Positive streptococcal antifibrinolysin tests are generally regarded as indicative of the presence of a specific “antibody.” There are instances, however, when this seems unlikely. Milstone5 has recently demonstrated that the plasma-clots of rabbits are resistant to lysis by human strains of hemolytic streptococci because they lack a substance—“lytic factor”—which is present in normal human serum. The addition of “lytic factor” to rabbit plasma results in rapid liquefaction of the clot by fibrinolysin. This observation was of considerable interest to us because of its possible clinical application since it might explain some of the apparently non-specific positive antifibrinolysin tests (resistant clots) which we have observed in infants and children. Newborn blood frequently gives a positive test in spite of the fact that there is no clinical or bacteriological evidence of a recent hemolytic streptococcal infection in the mother and her test is negative., As a starting point for the present study the blood from newborn infants was chosen first for comparison with the blood of children with positive tests following a hemolytic streptococcal infection. It seemed likely that newborns would generally have resistant plasma-clots for only one of two reasons—either because of absence of a substance or because of the presence of antifibrinolysin. In sick children both of these factors might be involved. This study represents a comparison of the blood of 10 normal newborns with that of 10 children who were convalescing from scarlet fever and other hemolytic streptococcal infections. All had maximally positive streptococcal antifibrinolysin tests. Methods The routine antifibrinolysin tests was performed as originally described by Tillett and Garner. 0.2 cc of human plasma was diluted with 0.8 cc of normal salt solution. To this was added 0.5 cc of an 18-hour broth culture of hemolytic streptococcus (known to dissolve normal plasma-clots in 15 minutes).