Proficiency Testing in a Laboratory Accreditation Program for the Bacterial Ring Rot Pathogen of Potato.

Area of Science:

• Plant Pathology
• Analytical Chemistry
• Microbiology

Background:

• Accurate detection of Clavibacter michiganensis subsp. sepedonicus is crucial for potato crop health.
• Enzyme-linked immunosorbent assay (ELISA) and immunofluorescence are common diagnostic methods.
• Understanding test variability is essential for reliable diagnostics and quality control.

Purpose of the Study:

• To quantify the repeatability and reproducibility of ELISA and immunofluorescence assays for Clavibacter michiganensis subsp. sepedonicus detection.
• To assess the performance of these methods using proficiency testing data.
• To evaluate the suitability of z-scores for monitoring analyst performance.

Main Methods:

• Analysis of data from eight laboratories participating in a proficiency testing program.
• Calculation of standard deviations for repeatability and reproducibility for both ELISA and immunofluorescence.
• Application of the Association of Official Analytical Chemists (AOAC) z-score procedure for performance evaluation.

Main Results:

• ELISA showed small repeatability standard deviation, increasing with absorbance; reproducibility standard deviation was larger and also increased at high absorbances.
• Immunofluorescence repeatability and reproducibility standard deviations were similar and increased with bacterial concentration.
• Over 90% of ELISA z-scores and 80% of immunofluorescence z-scores fell within the acceptable range.

Conclusions:

• Both ELISA and immunofluorescence are reliable methods for detecting Clavibacter michiganensis subsp. sepedonicus in potato tissue.
• Z-scores effectively evaluate analyst proficiency, with potential application in quality control systems.
• The study highlights the importance of inter-laboratory validation for diagnostic test accuracy.