Sorting out difficulties in immunological diagnosis of neurocysticercosis: Development and assessment of real time loop mediated isothermal amplification of cysticercal DNA in blood

Purpose of the study: Among various immunological tests available for diagnosis of neurocysticercosis (NCC), only EITB (Electroimmunotransfer blot for detection of anticysticercal antibodies) had gained widespread acceptance. However EITB is not available widely and is costly (Indian rupees 15,000/- approximately). We evaluated utility of Loop mediated isothermal amplification (LAMP) assay for detection of Taenia solium cox1 gene in blood of patients with NCC. Patients and methods: Current study included 100 consecutive patients of NCC at a tertiary teaching hospital in Northern India. All the patients underwent detailed history and examinations as well as gadolinium enhanced magnetic resonance imaging of brain. LAMP assay was performed in all the patients. The results were compared with 50 controls. Results: LAMP detected Taenia Solium cox1 gene in 74% of all blood samples in patients of NCC.The overall sensitivity of LAMP assay for detection of cox1 gene was 74% in all patients with NCC, 71.8% in patients with intraparenchymal brain cysts only and 86.7% of patients with extraparenchymal brain cysts with or without intraparenchymal brain cysts. The overall specificity of LAMP assay was 90% in all these three subgroups. The positive predictive value of real time LAMP assay was close to 93% for almost all forms of NCC- both solitary and multiple while negative predictive value ranged from 57 to 64%. Conclusion: Real time LAMP assay of blood for detection of Taenia solium cox1 gene appears to be a promising toll for diagnosis of NCC.