Preliminary investigations on the diagnostic value of passive hemagglutination and complement fixation tests in infections with Mycoplasma pneumoniae.

In order to evaluate the efficiency of passive hemagglutination (PHA) and complement fixation (CF) tests for the diagnosis of M. pneumoniae infections, 144 serum samples--out of which 81 from patients with respiratory and cutaneous infections and 63 from subjects with other diseases (controls)--were comparatively investigated by the two methods. The PHA test made evident a positivity index of 65% in the case of mixed pneumonias, as against 17% in controls, while the results obtained by CF were almost identical in the two groups investigated. The high specificity and sensitivity of the PHA reaction recommend this method for the diagnosis of acute M. pneumoniae infections.

Passive hemagglutination and complement fixation reactions in the early diagnosis of Mycoplasma pneumoniae infections.

Complement fixation (CF) and passive hemagglutination (PHA) tests (the latter with a M. pneumoniae antigen coupled by glutaraldehyde onto red blood cells) were performed in 263 patients with various infectious diseases (mostly in the 1st and 2nd week after onset) and non-infectious ones. CF reaction proved to be inappropriate for the early etiological diagnosis of mycoplasma infections, since the high titers were distributed undifferentially among the various patient groups and many sera (38%) showed anticomplementary activity. A PHA titer of at least 1/128 (preferably of 1/512) points to the presence of a M. pneumoniae infection, especially if clinical, radiological and laboratory data suggest a nonbacterial or mixed pneumonia. The diagnosis is often early enough to orientate the etiological therapy towards macrolides and tetracyclines. The PHA reaction recommended is specific, sensitive, reproducible and easy to perform.