Diagnosis of Leptospirosis in Febrile Patients of Golestan Province, Iran: Serology versus PCR

Introduction: Leptospirosis is a significant public health problem in the Caspian littoral of Iran comprising Gilan, Mazandaran, and Golestan provinces.  In Golestan province, serology assays indicated anti-Leptospira antibodies in animals and humans; however, no reliable record of infections in patients with signs and symptoms of the disease is available. Methods: We employed the indirect immunofluorescent antibody assay (IFA), and two PCR assays, a real-time PCR (qPCR) and a nested-PCR targeting ۱۶S rDNA (rrs) sequence for diagnosis of leptospirosis in febrile patients in Golestan province. Results: Out of ۵۲ febrile patients, ۲۵ (۴۸.۰۷%) had antibody titers ≥۱/۸۰ by IFA, and were defined as positive. In ۷, ۹, and ۷ individuals, the antibody titers were ۱/۴۰, ۱/۲۰, and ۱/۱۰, respectively, and ۴ had no antibodies. The qPCR and nested PCR detected leptospiral DNA in ۵۵.۷۵% and ۶۷.۳% of the patients' sera, respectively. The two PCR assays had a Kappa agreement of ۰.۵۳ (P< ۰.۰۰۰۱), suggesting a moderate agreement, and showed a significant reverse association with the IFA titers (P<۰.۰۵). Conclusion: Our results suggest that higher antibody titers accompanied the spirochete's removal from blood by the patient's immune response. Hence, a reliable diagnosis of Leptospira infection necessitates deploying a DNA-based method alongside serology.

Keywords:

Leptospirosis , IFA , PCR , Golestan , Iran , Diagnosis , Kappa statistics