Comparison of different serological methods for the determination of antibodies to Chlamydia psittaci in pigeon sera.

Several methods for detecting antibodies to Chlamydia psittaci using sera from pigeons were compared with regard to their sensitivity, specificity and efficacy. The reference method used was indirect immunofluorescence (IFI), which uses as antigen intracellular inclusions in McCoy cell monolayers. Indirect micro-immunofluorescence (MIF) using as antigen C. psittaci cultured on yolk sacs of embryonated eggs, direct and indirect complement fixation tests (CFT and ICFT, respectively), and enzyme-linked immunosorbent assay (ELISA) were compared to the reference method. Indirect micro-immunofluorescence proved to be the most efficient method, while ELISA was the most sensitive, though showing a very low specificity. No statistically significant difference was found in comparing the two complement fixation tests. The use of ICFT to check for the negative results obtained in CFT is questioned. Possible reasons for the different results with the methods used are discussed.