The performance of a point-of-care test for the diagnosis of Neurocysticercosis in a resource-poor community setting in Zambia - a diagnostic accuracy study

Abstract

Background: Neurocysticercosis (NCC) is the main cause of epilepsy in Taenia solium endemic rural communities. NCC diagnosis is difficult due to unavailability and unaffordability of serologic assays and neuroimaging. This study aimed to assess the performance of a cheap, novel T. solium lateral-flow point-of-care (TS POC) test for the diagnosis of NCC in a community setting.

Methods: A diagnostic accuracy study with prospective data collection, using a two-stage design was conducted in Sinda district of the Eastern province of Zambia between December 2017 and June 2019. Eligible participants were tested with the TS POC test. Thereafter, participants with a TS POC CC+ result and a subset of participants with a TS POC CC- result were subjected to serological testing for reference assays, and cerebral computed tomography (CT) for the reference diagnosis of NCC.

Findings: A total of 1249 participants were tested with the TS POC of which 177 (14%) were positive. Of the 151 TS POC CC+ and 82 TS POC CC- participants with cerebral CT examination, 35 TS POC CC+ and 10 TS POC CC-, respectively, had NCC. The sensitivity of the TS POC CC strip was 26% (uncertainty interval [UI] 15-41) for any type of NCC, which was similar to that estimated for the rT24H-EITB (23%, UI 8-48) and the serum antigen ELISA (30%, UI 11-58). The specificity was 88% (UI 85-90) for the TS POC, 89% (UI 79-94) for the rT24H-EITB, and 82% (UI 71-89) for the antigen ELISA. For NCC with active stage lesions, sensitivity was >99% (UI 58->99) for the TS POC, 76% (UI 40-94) for the rT24H-EITB and 76% (UI 39-94) for the antigen ELISA.

Interpretation: The TS POC CC had a promising sensitivity for diagnosis of participants with active NCC lesions within a community-based setting. Accuracy for NCC at any stage was limited for all tests (TS POC, rT24H-EITB and antigen ELISA). With further development the TS POC CC may enable a better detection and faster referral of NCC patients who may benefit from antiparasitic treatment.

Funding: European and Developing Countries Clinical Trials Partnership (EDCTP) and the German Federal Ministry of Education and Research (BMBF).

Keywords: Antigen ELISA; Diagnosis; Neurocysticercosis; Point-of-care test; Taenia solium; rT24H-EITB.

Fig. 1

Flowchart of the study to assess the performance of the TS POC CC test strip (index test) for the detection of NCC.

Fig. 2

Study area Sinda district.

Fig. 3

TS POC CC results and serological reference tests by NCC status (disaggregated by A: active-stage NCC, B: only calcified stage lesions, C: No NCC); numbers on the bars indicate the number of NCC lesions. Each column represents one participant unless indicated differently by a number in the box. EITB, Electroimmunotransfer blot; ELISA, Enzyme linked immunosorbent assay; rT24H, Recombinant protein for Taenia solium; TS POC CC, Taenia solium point-of-care cysticercosis test. Note that the POC negatives are underrepresented in this figure.

Fig. 4

Comparison of the performance of TS POC CC and serological tests for the diagnosis of NCC and active NCC. EITB, Electroimmunotransfer blot; ELISA, Enzyme linked immunosorbent assay; rT24H, Recombinant protein for Taenia solium; TS POC CC, Taenia solium point-of-care cysticercosis test.