Leishmaniasis direct agglutination test: using pictorials as training materials to reduce inter-reader variability...

Area of Science:

• Medical Diagnostics
• Parasitology
• Public Health

Background:

• The Direct Agglutination Test (DAT) is a key diagnostic tool for Visceral Leishmaniasis (VL), despite potential inter-reader variability due to subjective interpretation.
• Standardization of DAT is essential for reliable diagnosis in endemic regions.

Purpose of the Study:

• To assess inter-laboratory agreement in DAT results for VL diagnosis.
• To propose and evaluate a pictorial-based approach for standardizing DAT result interpretation.

Main Methods:

• A proficiency panel of 15 sera was distributed to nine laboratories across different continents.
• Inter-laboratory agreement was calculated pre- and post-refresher training, including on-site training with photographic aids.
• Statistical analysis, including the Wilcoxon rank-sum test, was used to evaluate changes in concordance and variance.

Main Results:

• Initial concordance with reference laboratories was 50%, improving to 84% after training.
• Agreement on negative sera increased from 94% to 98% post-training.
• Variance in titre readings significantly decreased from 3.3 to 1.0 titres after implementing standardized training.

Conclusions:

• Subjective endpoint reading is the primary cause of disagreement in DAT results.
• Pictorial training materials effectively reduce result disparity and promote standardized DAT reading without compromising diagnostic sensitivity for VL.