A Prospective Study of the Persistence of Mycoplasma Pneumoniae Antibody Levels

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Abstract
Sera from 13 patients with initial complement fixation (CF) titres of 160 or above, and from 5 with rising titres to Mycoplasma pneumoniae were tested at 2-monthly intervals for CF antibodies and for cold agglutinins. In an attempt to differentiate between ‘early’ and ‘late’ sera with raised titres, initial sera and those, taken 6 to 8 months later, with a CF titre of 160 or above were tested by the metabolic inhibition test and also treated with 2-mercaptoethanol (2ME). Cold agglutinins were detected in 5 of the 13 initial sera but in none of the 7 ‘late’ sera with raised CF titres. A 4-fold or greater fall in the CF titre after treatment with 2ME occurred in 5 of the 12 initial sera tested, and in one of the 7 ‘late’ sera. Metabolic inhibiting antibodies were present in 7 of the 12 initial sera and in 4 of the 6 ‘late’ sera tested. In only one patient with a raised initial CF titre but no cold agglutinins and no 2ME effect was there later evidence of a current infection with M. pneumoniae. Cold agglutinins were present and/or there was a 2ME effect in the initial sera from all 5 patients with rising titres. It is concluded that a combination of cold agglutinins and the effect of 2ME on the CF titres will help to differentiate ‘early’ from ‘late’ sera with significantly raised CF antibodies.