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

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.

We employed the indirect immunofluorescent antibody assay (IFA), and two PCR assays, a real-time PCR (qPCR) and a nested-PCR targeting 16S rDNA (rrs) sequence for diagnosis of leptospirosis in febrile patients in Golestan province.

Out of 52 febrile patients, 25 (48.07%) had antibody titers ≥1/80 by IFA, and were defined as positive. In 7, 9, and 7 individuals, the antibody titers were 1/40, 1/20, and 1/10, respectively, and 4 had no antibodies. The qPCR and nested PCR detected leptospiral DNA in 55.75% and 67.3% of the patientschr('39') sera, respectively. The two PCR assays had a Kappa agreement of 0.53 (P< 0.0001), suggesting a moderate agreement, and showed a significant reverse association with the IFA titers (P<0.05).

Our results suggest that higher antibody titers accompanied the spirochetechr('39')s removal from blood by the patientchr('39')s immune response. Hence, a reliable diagnosis of Leptospira infection necessitates deploying a DNA-based method alongside serology.