EVALUATION OF PCR AND ELISA-IgM RESULTS IN THE LABORATORY DIAGNOSIS OF CRIMEAN-CONGO HAEMORRHAGIC FEVER CASES IN 2008 IN TURKEY

Crimean-Congo hemorrhagic fever (CCHF) is a fatal zoonotic viral haemorrhagic infection described in Africa, Asia, Eastern Europe, and the Middle East. CCHF virus (CCHFV) classified in Bunyaviridae family and Nairovirus genus, is transmitted to humans by tick (Hyalomma and Ixodid) bites and human to human transmission may occur by direct contact with blood or other infected tissues. The disease became endemic and a public health problem since 2002 outbreak in Turkey. The specific laboratory diagnosis and confirmation of the disease is performed in Refik Saydam National Public Health Agency, by using molecular and serological methods. For this purpose serum and/or plasma samples from suspected CCHF patients are submitted to the reference laboratory with an official "possible case report form". According to the algorithm in our laboratory, the first samples which were sent from possible acute cases were searched initially by an in-house real time-polymerase chain reaction (PCR) method and those which were found negative with PCR, were then studied by in-house ELISA method in terms of CCHF-IgM antibodies. In 2008, a total of 4634 samples obtained from 2855 CCHF suspected patients have been examined for the positivity of CCHFV, and 1315 (46%) cases were found to be positive by molecular and/or serologic methods. The aim of this study was to evaluate the results of 726 cases whose at least 2 samples were sent to laboratory, with at least 1 positivity in at least 1 clinical sample with either PCR or IgM ELISA, or both, and with complete informations in possible case report form, during 2008 in Turkey. The positive results were also analyzed according to the starting date of the complaints and the date samples received in order to evaluate the positivity rates of molecular and serological methods with regard to the time. The first serum samples in 94.1% (683/726) of cases were found to be positive with PCR and/or ELISA-IgM methods. PCR positivity was found as 78.1% (5671726), while CCHFV-IgM positivity was detected in 116 (72.9%) in the remaining 159 PCR negative samples. In the first sera, PCR and ELISA results were evaluated in relation to the start of complaints and the date samples received. After the onset of symptoms, PCR positivity was determined as 83.4% in the samples taken in the first 5 days, and reduces to 67.5% in the samples between 6-10 days. The detection rate of CCHFV-IgM increases up to 95% when PCR positivity rate decreases after the 5(th) day. As expected, positivity is determined to be high by PCR in the first days, and ELISA-IgM after the 5(th) day. In conclusion, recording clinical data such as the onset of disease and the date of sample received ensure the accurate evaluation of the disease and the laboratory results are reliably accomplished in a short time