Veterinary parasitology2021; 296; 109509; doi: 10.1016/j.vetpar.2021.109509

What makes a good fecal egg count technique?

Nielsen, MK

Abstract: The first parasite fecal egg counting techniques were described over 100 years ago, and fecal egg counting remains essential in parasitology research as well as in clinical practice today. Several novel techniques have been introduced and validated in recent years, but this work has also highlighted several current issues in this research field. There is a lack of consensus on which diagnostic parameters to evaluate and how to properly design studies doing so. Furthermore, there is a confusing and sometimes incorrect use of terminology describing performance of fecal egg counting techniques, and it would be helpful to address these. This manuscript reviews qualitative and quantitative diagnostic performance parameters, discusses their relevance for fecal egg counting techniques, and highlights some of the challenges with determining them. Qualitative parameters such as diagnostic sensitivity and specificity may be considered classic diagnostic performance metrics, but they generally only have implications at low egg count levels. The detection limit of a given technique is often referred to as the "analytical sensitivity", but this is misleading as the detection limit is a theoretically derived number, whereas analytical sensitivity is determined experimentally. Thus, the detection limit is not a diagnostic performance parameter and does not inform on the diagnostic sensitivity of a technique. Quantitative performance parameters such as accuracy and precision are highly relevant for describing the performance of fecal egg counting techniques, and precision is arguably the more important of the two. An absolute determination of accuracy can only be achieved by use of samples spiked with known quantities of parasite ova, but spiking does not necessarily mimic the true distribution of eggs within a sample, and accuracy estimates are difficult to reproduce between laboratories. Instead, analysis of samples from naturally infected animals can be used to achieve a relative ranking of techniques according to egg count magnitude. Precision can be estimated in a number of different approaches, but it is important to ensure a relevant representation of egg count levels in the study sample set, as low egg counts tend to associate with lower precision estimates. Coefficients of variation generally provide meaningful measures of precision that are independent of the multiplication factor of the techniques evaluated. Taken together, there is a need for clear guidelines for studies validating fecal egg counting techniques in veterinary parasitology with emphasis on what should be evaluated, how studies could be designed, and how to appropriately analyze the data. Furthermore, there is a clear need for better consensus regarding use of terminology describing the diagnostic performance of fecal egg count techniques.

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Publication Date: 2021-06-27 PubMed ID: 34218175DOI: 10.1016/j.vetpar.2021.109509Google Scholar: Lookup

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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research article evaluates and provides guidance on different techniques used for counting parasitic eggs in fecal samples, critiquing various qualitative and quantitative parameters and highlighting the need for better standardization in the field.

Introduction

The study delves into fecal egg counting techniques which are an essential part of parasitology research and veterinary clinical practice. The paper critiques the current issues including lack of consensus in the evaluation process, improper design of research studies and incorrect use of terminology.

Qualitative Parameters

The authors focus on diagnostic sensitivity and specificity as major qualitative diagnostic metrics. However, they assert these parameters are significant only at lower egg count levels.
They clarify that the term “analytical sensitivity” is often incorrectly used to mean the detection limit. They emphasize that these two are distinct, as detection limit is theoretically derived whereas analytical sensitivity is experimental.

Quantitative Parameters

The authors further discuss accuracy and precision as vital quantitative performance parameters.
They opine that precision outweighs accuracy and a good measure of precision is detailed in the study through variation coefficients.
They critically disapprove that absolute accuracy can only be determined with spiked samples. They argue that spiking does not truly represent the egg’s distribution in a sample and that such determinations are tough to reproduce in different labs.
Instead, they recommend using samples from naturally infected animals to rank techniques relative to egg count size.

Proposed Guidelines

The article ends with a call for clear guidelines on validating fecal egg counting methods in veterinary parasitology. This includes recommendations on what should be evaluated, how studies should be structured, and the data analysis procedure.
The authors also stress the need for a consensus on terminologies used in discussing the diagnostic performance of these techniques.

Cite This Article

APA

Nielsen MK. (2021). What makes a good fecal egg count technique? Vet Parasitol, 296, 109509. https://doi.org/10.1016/j.vetpar.2021.109509

Publication

Veterinary parasitology

ISSN: 1873-2550

NlmUniqueID: 7602745

Country: Netherlands

Language: English

Volume: 296

Pages: 109509

PII: S0304-4017(21)00168-0

Researcher Affiliations

Nielsen, Martin K

M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA. Electronic address: martin.nielsen@uky.edu.

MeSH Terms

Animals
Feces / parasitology
Ovum
Parasite Egg Count / standards
Parasite Egg Count / veterinary
Parasitology / methods
Sensitivity and Specificity

Citations

This article has been cited 16 times.

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