Understanding the relationship between prevalence of microfilariae and antigenaemia using a model of lymphatic filariasis infection

Abstract

BackgroundLymphatic filariasis is a debilitating neglected tropical disease that affects impoverished communities. Rapid diagnostic tests of antigenaemia are a practical alternative to parasitological tests of microfilaraemia for mapping and surveillance. However the relationship between these two methods of measuring burden has previously been difficult to interpret.MethodsA statistical model of the distribution of worm burden and microfilariae (mf) and resulting antigenaemic and mf prevalence was developed and fitted to surveys of two contrasting sentinel sites undergoing interventions. The fitted model was then used to explore the relationship in various pre- and post-intervention scenarios.ResultsThe model had good quantitative agreement with the data and provided estimates of the reduction in mf output due to treatment. When extrapolating the results to a range of prevalences there was good qualitative agreement with published data.ConclusionsThe observed relationship between antigenamic and mf prevalence is a natural consequence of the relationship between prevalence and intensity of adult worms and mf production. The method described here allows the estimation of key epidemiological parameters and consequently gives insight into the efficacy of an intervention programme.

Understanding the relationship between egg- and antigen-based diagnostics of Schistosoma mansoni infection pre- and post-treatment in Uganda

“…Having multiple diagnostics for a particular disease is becoming more common, but connecting the alternative diagnostics can prove challenging. In neglected tropical diseases, new studies are being done in this scope, such as the work by Irvine et al [ 34 ] in lymphatic filariasis diagnostics. Understanding the interactions between the different diagnostic tools is important, particularly for diseases such as schistosomiasis that have ambitious targets for control and elimination by 2020.…”

Combining different diagnostic studies of lymphatic filariasis for risk mapping in Papua New Guinea: a predictive model from microfilaraemia and antigenaemia prevalence surveys

“…Considering previous indications that the relationship between Mf and antigen diagnostics changes with the presence of MDA [ 26 – 28 ], we began by averaging ICT and Og4C3 values for surveys that reported more than one antigen test. We then conducted an ANOVA test between prevalence values from surveys conducted before and after any MDA, for both Mf and antigen results separately.…”

“…The two other diagnostic tests detect antigen from the adult worms instead [ 23 ]. Efforts to understand the relationship between these types of diagnostics have been inconclusive [ 25 , 26 ] but remain crucial for combining varying types of diagnostic results to develop risk maps of LF in the region [ 26 ]. Thus, the association between Mf detection and antigen results remains an important research question.…”

“…Few studies have explored this association, generally concluding that these two variables lack a predictive relationship that could be used to combine results in studies [ 25 ]. While efforts using logistic regression were unable to produce a predictive model [ 25 ], further approaches have proposed that a relationship between these two diagnostic types exists, and it is based on the distribution of adult worms and their Mf output [ 26 ]. These studies suggest that the relationship between Mf and antigen diagnostics changes with the presence of MDA deployment [ 25 , 26 ], as its implementation effectively reduces the number of Mf, but it takes time to kill off the adult worms which continue to produce antigen in the bloodstream.…”

A geostatistical framework for combining spatially referenced disease prevalence data from multiple diagnostics

“…Alternatively, subject matter knowledge could be used to constrain the admissible forms for and ; see, for example, Irvine et al . () who derive a functional relationship between MF and an immuno‐chromatographic test for prevalence of lymphatic filariasis by making explicit assumptions on the distribution of worms and their reproductive rate in the general population.…”