ELISA in the Evaluation of Therapeutic Response to Albendazole in Neurocysticercosis

Background: Immunological tests are frequently used in the diagnosis of neurocysticercosis (NC), but scant literature is available on the efficacy of these tests in the assessment of therapeutic response. An ELISA using the Cysticercus fasciolaris larval stage of T. taeniaeformis has been evaluated in the post-treatment follow-up of NC in a cohort of 165 cases.

Methods: Cases (n=165) with at least one active cyst documented by computed tomography and a positive pre-treatment serum ELISA for IgG and/or IgM antibodies were treated with albendazole. CT scan and ELISA tests were repeated at 6 months in 148 cases who returned for follow-up.

Results: A radiological response was observed in 132 of 148 cases at follow-up. Sixteen cases were non-responders. Amongst the responders, 111/128 (IgG) and 93/117 (IgM) respectively had converted to negative antibody titers at 6 months. Thirteen of 16 and 12 of 15 non-responders continued to show high anti-Cysticercus IgG and IgM titers. IgG ELISA, IgM ELISA and combined IgG and IgM results exhibited a sensitivity (%) of 81.3, 80.0 and 100, a specificity (%) of 86.7, 79.5 and 72.0, a positive predictive value (PV%) of 97.4, 96.9 and 30.2, and a negative PV(%) of 97.4, 96.9, 100 respectively.

Conclusion: IgG ELISA is a sensitive and specific tool to assess treatment response. A negative ELISA result for both IgG and IgM antibodies denotes a cure. While ELISA cannot replace the visual confirmation provided by radiological imaging in follow-up, the addition of an ELISA test may help overcome the limitations in interpretation of CT scans.