Multi-center evaluation of a user-friendly lateral flow assay to determine IP-10 and CCL4 levels in blood of TB and non-TB cases in Africa

Abstract

Objective: Multi-center evaluation of a user-friendly lateral flow test for detection of IP-10 and CCL4 levels in Mycobacterium tuberculosis (Mtb) antigen-stimulated whole blood samples from tuberculosis (TB) suspects.

Design and methods: A quantitative lateral flow (LF)-based assay platform was applied to detect chemokines IP-10 and CCL4. Chemokine quantitation was achieved using interference-free, fluorescent up-converting phosphor (UCP) labels. The new assays allowed worldwide shipping and storage without requiring a cold chain and were tested at seven institutes (including Ethiopia, Malawi, The Gambia, South Africa, Uganda and Namibia) employing portable lightweight readers for detection of the UCP label. At each site, clinical samples, confirmed TB and non-TB (i.e. other respiratory diseases (ORD)) cases, were collected and analyzed simultaneously with quality control (QC) human IP-10 or CCL4 standards.

Results: Performance of the UCP-LF assay in Africa using QC standards indicated high robustness allowing quantitative detection between 100 and 100,000pg/mL. The optimized assays allowed successful determination of chemokine levels using 1μL whole blood sample from the locally recruited subjects with TB or ORD.

Conclusion: This African multi-center trial further demonstrated the applicability of the low-tech and robust UCP-LF platform as a convenient quantitative assay for chemokine detection in whole blood. Ambient shipping and storage of all assay reagents and the availability of lightweight standalone readers were acknowledged as essential requirement for test implementation in particular in remote and resource-limited settings.

Keywords: CCL4; Chemokine; Diagnosis, field-friendly, lateral flow; IP-10; Tuberculosis; Up-converting phosphor, UCP.