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Home / Equine Research Bank / Vet Parasitol X / The effect of counting duration on quantitative fecal egg co...
Veterinary parasitology: X2019; 2; 100020; doi: 10.1016/j.vpoa.2019.100020

The effect of counting duration on quantitative fecal egg count test performance.

Abstract: Fecal egg counts are the primary diagnostic tools of equine parasitology and use of the McMaster test and its variants in clinical practice is widely recommended. Manual counting is, however, prone to various sources of human error. For example, in real-world situations analysts can be under significant pressure to process high numbers of samples in a limited time. This practice could affect test result quality, but yet no studies have determined whether this is the case. This study's purpose was to assess the effect of shortened counting duration (from either restricting counting time or counting only one grid of a slide) on McMaster test performance, and to compare the results to those of an automated test whose output is not subject to such limitations. Fifteen fecal samples from horses infected with strongylid parasites were divided equally into three groups based on high, medium and low levels of egg content (201-500, 501-1000 and 1001+ eggs/g). Slurries were produced from each sample and 10 subsamples of each were counted by both the McMaster and automated methods. McMaster slides were first counted at leisure, and then twice again with counting time being restricted to either one or two min. The effect of reducing sample processing time by counting only one grid of the McMaster slide was also assessed. Counting for one min significantly decreased manual egg counts by 50-60% relative to counts conducted at leisure (p < 0.001). While these decreases were somewhat ameliorated by counting for two min, the results were still approximately 10% lower than the at-leisure counts, a difference that was also statistically significant (p < 0.001). Furthermore, restricted counting duration also resulted in a significant decrease of approximately one-third in McMaster test precision, as assessed by the coefficients of variation (CoVs) of the 10 replicates of each sample, as did counting just a single grid of the McMaster slide. These differences effectively further improved the observed superior precision of the automated method compared to at-leisure manual McMaster counting, and the automated counts and their precision remained relatively unaffected following multiple analyses of the same processed samples. Taken together, these results indicate that analysists should carefully assess the possible effects on test performance of modifications to standard egg-counting procedures that are designed to account for real-world pressures, in order to achieve an optimal compromise between test accuracy and precision on one hand and practicality on the other.
© 2019 The Authors.
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Publication Date: 2019-11-18 PubMed ID: 32904743PubMed Central: PMC7458370DOI: 10.1016/j.vpoa.2019.100020Google Scholar: Lookup
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  • Journal Article

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.

The research investigates the impact of counting time on the performance of the McMaster fecal egg count test, a primary tool for diagnosing equine parasites. The results indicate that both reducing the counting duration and only inspecting one grid of the slide significantly affect the test results and precision.

Objective of the Study

  • The primary goal of this research was to understand how the duration of manual egg counting and the decision to only count one grid of the slide during the McMaster test could impact its results and precision.
  • The study also compares the McMaster method’s performance under different conditions to an automated test, which is not sensitive to such limitations.

Methods Used

  • Fifteen fecal samples from horses infected with strongylid parasites were divided into three groups based on egg content levels (high, medium and low).
  • Each sample was then turned into a slurry, and 10 subsamples were prepared and counted using both the McMaster and automated methods.
  • The McMaster slides were first counted without time restrictions (“at leisure”), then counted again twice under time-constrained conditions.
  • Additionally, the impact of counting just one grid of the McMaster slide was assessed as a measure of reducing sample processing time.

Key Findings

  • Limiting the counting duration to one minute led to a significant decrease in egg counts by 50-60% compared to leisurely counting (p < 0.001).
  • While extending the counting duration to two minutes improved the counts, the results were still around 10% lower than leisurely counts, a statistically significant difference (p < 0.001).
  • Counting duration restrictions also reduced the precision of the McMaster test by approximately one-third, as did counting only one grid of the slide.
  • The automated egg counting method demonstrated superior precision compared to manual McMaster counting, practically unaffected by multiple sample analyses.

Implications

  • The outcomes suggest that it is essential for analysts to consider how amendments to standard egg-counting procedures, made to accommodate real-world pressures, might influence test performance.
  • There needs to be a balance between test accuracy and precision and practical constraints to ensure valid and reliable results.

Cite This Article

APA
Slusarewicz M, Slusarewicz P, Nielsen MK. (2019). The effect of counting duration on quantitative fecal egg count test performance. Vet Parasitol X, 2, 100020. https://doi.org/10.1016/j.vpoa.2019.100020

Publication

Veterinary parasitology: X
ISSN: 2590-1389
NlmUniqueID: 101755316
Country: Netherlands
Language: English
Volume: 2
Pages: 100020
PII: 100020

Researcher Affiliations

Slusarewicz, Megan
  • MEP Equine Solutions, 3905 English Oak Circle, Lexington, KY 40514, USA.
Slusarewicz, Paul
  • MEP Equine Solutions, 3905 English Oak Circle, Lexington, KY 40514, USA.
  • M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, 1400 Nicholasville Road, Lexington, KY 40546, USA.
Nielsen, Martin K
  • M.H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, 1400 Nicholasville Road, Lexington, KY 40546, USA.

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Citations

This article has been cited 3 times.
  1. Johnson WL, Reynolds S, Adkins CL, Wehus-Tow B, Brennan J, Krus CB, Buttke D, Martin JM, Jesudoss Chelladurai JRJ. A comparison of Mini-FLOTAC and McMaster techniques, overdispersion and prevalence of parasites in naturally infected North American bison (Bison bison) in the USA. Curr Res Parasitol Vector Borne Dis 2022;2:100103.
    doi: 10.1016/j.crpvbd.2022.100103pubmed: 36437837google scholar: lookup
  2. Ghafar A, Abbas G, King J, Jacobson C, Hughes KJ, El-Hage C, Beasley A, Bauquier J, Wilkes EJA, Hurley J, Cudmore L, Carrigan P, Tennent-Brown B, Nielsen MK, Gauci CG, Beveridge I, Jabbar A. Comparative studies on faecal egg counting techniques used for the detection of gastrointestinal parasites of equines: A systematic review. Curr Res Parasitol Vector Borne Dis 2021;1:100046.
    doi: 10.1016/j.crpvbd.2021.100046pubmed: 35284858google scholar: lookup
  3. Mirzaei A, Rahmani Shahraki A, Maunsell FP, Diehl BN. Evaluation of the Diagnostic Performance and Validation of an AI-Assisted Fluorescence Imaging Device for Fecal Egg Counts Against the Manual McMaster Reference Method in Kiko Male Goats. Animals (Basel) 2026 Jan 14;16(2).
    doi: 10.3390/ani16020248pubmed: 41594438google scholar: lookup
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