Comparison of diagnostic potential of serological, molecular and cell culture methods for detection of Q fever in ruminants

Q fever is an infectious disease caused by Coxiella burnetii. Diagnosis of Q fever based on clinical symptoms is unattainable; thus, different laboratory techniques are used to detect the infection. The aim of the study was to compare the diagnostic potential of ELISA, CFT, conventional PCR, real-time PCR and cell culture. The tests were carried out on 2251 serum samples from ruminants. Moreover, 668 placentas, 1277 vaginal swabs and 306 specimens of the internal organs of aborted foetuses were examined by PCR and cell culture. Pearson's chi-square test was used to compare the results obtained by ELISA, CFT, PCR, real-time PCR and isolation in cell culture. The χ2 test confirmed that in most cases the results obtained by means of the different methods were correlated with each other (P < 0.05). The highest correlation coefficients (r = 0.76–0.87) were observed in the case of real-time PCR and conventional PCR. ELISA and CFT were moderately correlated (r = 0.43–0.45). When the comparison was made between the results of tests run on samples from swabs and aborted foetuses, the r values between ELISA and CFT were lower than those between ELISA and PCRs. A negligible, or weak to moderate relationship was mostly observed when the method of cell culture isolation was compared with all the other analytical techniques investigated. The use of a combination of different laboratory methods, preferably ELISA for serology and polymerase chain reactions for the agent detection, is suggested to achieve the correct diagnosis of Q fever.