Leptospirosis is an important re emerging zoonotic disease causing acute febrile illness in tropical regions including Tamil Nadu. Early diagnosis is challenging due to non specific clinical presentation and limited sensitivity of serological tests in the initial phase of illness. Microscopic agglutination test though considered the reference standard requires paired sera and is not useful for early clinical decision making. Polymerase chain reaction based methods can detect leptospiremia in the early acute phase and enable timely treatment.

This study aims to clinically evaluate a novel multiplex PCR panel named LEPTOPLEX targeting LipL21 LipL32 and LipL41 genes for the diagnosis of leptospirosis among clinically suspected adult patients in Kancheepuram district. Adult patients aged 18 to 65 years presenting with acute febrile illness suspected to be leptospirosis will be enrolled. Blood samples will be collected at baseline for LEPTOPLEX testing and compared with conventional PCR and serological testing. Convalescent samples will be collected for serological confirmation.

The primary outcome of the study is to assess the sensitivity and specificity of the LEPTOPLEX multiplex PCR assay at baseline during the acute phase of illness. Secondary outcomes include comparison of detection rates with conventional diagnostic methods assessment of turnaround time agreement with serological reference standard and gene wise positivity pattern.

The study is expected to generate evidence on the utility of LEPTOPLEX as a rapid and reliable diagnostic tool for early detection of leptospirosis and to support its potential use in endemic settings for improved case management and disease control