This study focuses on harmonising the competition ELISA (cELISA) assay for Plasmodium falciparum (P. falciparum), using the 1st WHO reference reagent for anti-malaria (P. falciparum) human reference serum (10/198). Antibody-mediated immune responses against the Apical Membrane Antigen 1 (AMA1) play a significant role in protection against malaria. However, the sequence diversity of AMA1 and cross-reactivity among variants pose challenges in assessing antibody responses. To address this, the cELISA assay was selected to examine cross-reactive antibody responses against different variants. The harmonisation process for cELISA was performed in three laboratories. The 10/198 served as an internal standard for the calculation of IgG concentrations in the cELISA using ADAMSEL software. Additionally, a novel semi-automated analytical tool was developed in the R-statistics environment. This tool is freely available for download and streamlines generating results while minimising human error. This study demonstrated the effectiveness of the 1st WHO reference reagent as a standard for cELISA. Additionally, the ADAMSEL software and R-platform tool provide a user-friendly and accessible tool for the analysis of cELISA data. Its automation capabilities improve efficiency and ensure global accessibility at no cost, benefitting laboratories with limited resources.