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Translating from egg- to antigen-based indicators for Schistosoma mansoni elimination targets: A Bayesian latent class analysis study
Clark, Jessica Moses, Arinaitwe Nankasi, Andrina Faust, Christina L. Adriko, Moses Ajambo, Diana Besigye, Fred Atuhaire, Arron Wamboko, Aidah Rowel, Candia
Clark, Jessica
Moses, Arinaitwe
Nankasi, Andrina
Faust, Christina L.
Adriko, Moses
Ajambo, Diana
Besigye, Fred
Atuhaire, Arron
Wamboko, Aidah
Rowel, Candia
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Abstract
Schistosomiasis is a parasitic disease affecting over 240-million people. World Health Organization (WHO) targets for Schistosoma mansoni elimination are based on Kato-Katz egg counts, without translation to the widely used, urine-based, point-of-care circulating cathodic antigen diagnostic (POC-CCA). We aimed to standardize POC-CCA score interpretation and translate them to Kato-Katz-based standards, broadening diagnostic utility in progress towards elimination. A Bayesian latent-class model was fit to data from 210 school-aged-children over four timepoints pre- to six-months-post-treatment. We used 1) Kato-Katz and established POC-CCA scoring (Negative, Trace, +, ++ and +++), and 2) Kato-Katz and G-Scores (a new, alternative POC-CCA scoring (G1 to G10)). We established the functional relationship between Kato-Katz counts and POC-CCA scores, and the score-associated probability of true infection. This was combined with measures of sensitivity, specificity, and the area under the curve to determine the optimal POC-CCA scoring system and positivity threshold. A simulation parametrized with model estimates established antigen-based elimination targets. True infection was associated with POC-CCA scores of ≥ + or ≥G3. POC-CCA scores cannot predict Kato-Katz counts because low infection intensities saturate the POC-CCA cassettes. Post-treatment POC-CCA sensitivity/specificity fluctuations indicate a changing relationship between egg excretion and antigen levels (living worms). Elimination targets can be identified by the POC-CCA score distribution in a population. A population with ≤2% ++/+++, or ≤0.5% G7 and above, indicates achieving current WHO Kato-Katz-based elimination targets. Population-level POC-CCA scores can be used to access WHO elimination targets prior to treatment. Caution should be exercised on an individual level and following treatment, as POC-CCAs lack resolution to discern between WHO Kato-Katz-based moderate- and high-intensity-infection categories, with limited use in certain settings and evaluations.
Citation
Clark, J., Moses, A., Nankasi, A., Faust, C. L., Adriko, M., Francoeur, R., ... & Prada, J. M. (2022). Translating From Egg-to Antigen-Based Indicators for Schistosoma mansoni Elimination Targets: A Bayesian Latent Class Analysis Study. Frontiers in Tropical Diseases, 3:825721. https://doi.org/10.3389/fitd.2022.825721
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Frontiers Media
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Frontiers in Tropical Diseases
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This Document is Protected by copyright and was first published by Frontiers. All rights reserved. it is reproduced with permission.
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2673-7515