[Value of the Twar strain for chlamydiosis serology. Choice of a strategy of detecting antibodies].

We examined 212 sera from patients with respiratory diseases (n = 55), from women regularly attending a gynaecology clinic (n = 155) and from patients with cat-scratch disease (n = 2), using the complement fixation test against Chlamydia psittaci and IgG indirect immunofluorescence tests against 3 different strains of C. psittaci, C. trachomatis (serotype L2) and the TWAR strain. Forty-one sera were positive. The TWAR strain raised the serological detection rate of antibodies to chlamydia up to 97.5 percent of sera which were initially positive with one and/or another of the four reactions used, as against 43.9 percent only for the two conventional indirect immunofluorescence reactions (anti-C. psittaci and anti-C. trachomatis); the increase was particularly marked in patients with respiratory diseases. Although it seems to be possible, in practice, to detect these antibodies using only the three indirect immunofluorescence tests, we continue to use the complement fixation test not only because it may be positive at the onset of infection, but also because it reflects immunological changes. Thus, the contribution of the TWAR strain to the laboratory diagnosis of chlamydial infection is considerable, and it is no longer possible to do without this strain in serological investigations.