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

Area of Science:

• Equine parasitology
• Veterinary diagnostics
• Parasitic disease management

Background:

• Fecal egg counts are crucial for diagnosing equine parasites.
• The McMaster test is widely used but susceptible to human error.
• Time pressures in clinical settings may impact diagnostic accuracy.

Purpose of the Study:

• To evaluate the impact of reduced counting duration on McMaster test performance.
• To compare manual McMaster counts with an automated method.
• To assess the effect of counting only one grid on test accuracy.

Main Methods:

• Fifteen fecal samples from infected horses were categorized by egg count.
• Subsamples were counted manually using the McMaster technique (leisure, 1 min, 2 min).
• A single grid count and an automated method were also employed for comparison.

Main Results:

• Reducing counting time to 1 minute decreased manual egg counts by 50-60%.
• A 2-minute count still resulted in ~10% lower counts.
• Restricted counting duration and single-grid counts significantly reduced test precision (increased CoVs).
• The automated method demonstrated superior precision and was less affected by repeated analysis.

Conclusions:

• Modifications to standard McMaster procedures to save time can compromise accuracy and precision.
• Automated methods provide a more reliable alternative for equine fecal egg counts.
• Careful consideration of test modifications is needed to balance practicality with diagnostic quality.