BSP Parasites Online 2021
Schedule : Back to Dr Jessica Clark

Standardising the interpretation of point-of-care circulating cathodic antigen diagnostics for Schistosoma mansoni: A Bayesian latent class analysis study

Time: To be announced
To be announced
Dr Jessica Clark


J Clark3; M Arinaitwe1; A Nankasi1; C L Faust3; M Adriko1; D Ajambo1; F Besigye1; A Atuhaire1; A Wamboko1; L V Carruthers3; R Francoeur3; E M Tukahebwe1; J M Prada2; P H L Lamberton3
1 Vector Control Division, Ministry of Health, Uganda;  2 University of Surrey, UK;  3 Institute of Biodiversity, Animal Health and comparative Medicine, and Wellcome Centre for Integrative Parasitology, University of Glasgow, UK


Background: Schistosomiasis is targeted by the World Health Organisation (WHO) for elimination as a public health problem (EPHP) by 2030, defined as a population having  ≤1% heavy infections by the Kato-Katz diagnostic. However, Kato-Katz lack sensitivity. The point-of-care circulating cathodic antigen (POC-CCA) tests are also recommended by WHO for Schistosoma mansoni diagnosis, but no guidance exists for their optimal interpretation, or analogous indicators of EPHP.

Methods: We developed a Bayesian latent-class model fit to parasitological data from 210 school-aged-children at four time points from pre-treatment to six-months post-treatment: one with Kato-Katz and POC-CCA+ (the standard POC-CCA scoring method: Negative, Trace, +, ++ and +++) and one Kato-Katz and G-Score (a newly developed scoring method from G1 (negative) to G10). Using parameter estimates, we simulated EPHP settings to establish an EPHP indicator analogous to Kato-Katz. 

Findings: The POC-CCA tests saturate at low infection intensities explaining the lack of correlation between WHO infection intensity categories and POC-CCA scores. Optimal positivity thresholds are + and G3. Scoring system performance was comparable, but fluctuated with treatment. The proportion of a population that has scores of ++ or +++, or G7 and above, can be used as cut offs for if a community has likely reached EPHP.

Interpretation: The POC-CCA cannot be aligned to individual-level egg-count morbidity indicators. POC-CCA policy guidelines should be provided in terms of population-level prevalence. That the performance of the POC-CCA fluctuates with time, indicates a changing relationship between egg production and antigen levels.

Hosted By

British Society for Parasitology (BSP)

We are science based charitable society.
Event Logo Find us on Facebook Follow us on Twitter