External quality assessment of the detection of rickettsioses in China

ObjectiveTo report a training course on the laboratory diagnoses of rickettsioses that 10 provincial/city CDCs participated in laboratory external quality assurance (EQA) based on the serological specific antibodies detection and rapid PCR amplifying targeted genes of rickettsiae.MethodsAn EQA program to evaluate the following laboratory procedures was developed to detect rickettsiae: (1) immunofluorescent assay (IFA) to detect specific antibodies of A. phagocytophilum, R. heilongjiangensis and O. tsutsugamshi respectively.(2) Two sets of nested PCR were used amplifying groEL genes for most members of the family Rickettsiaceae and amplifying 16SrRNA genes for the most members of family anaplasmae, respectively. A scoring scheme based on the distribution of the median antibody titer values of the serologic assays was designed and a ranking list of the scores of the PCR results based on the detected minimal copy numbers of reference DNA was created.ResultsAmong nine laboratories who reported the results on time, eight laboratories gave acceptable serologic results, the other one provided an unacceptable antibody titer (1:2 vs median 1:64) results for O. tsutsugamshi. The limits of detection (LOD) for the PCR amplifying for five references DNA ranged from 1copy/μ L to 106 copy/μ L.ConclusionWe successfully trained and popularized modern diagnostic methods of rickettsiae in 10 provincial CDCs in China and first conducted the EQA projects and evaluated the results.