Commutability of food microbiology proficiency testing samples

Area of Science:

• Food science
• Microbiology
• Analytical chemistry

Background:

• Proficiency testing (PT) is crucial for assessing laboratory analytical performance in food microbiology.
• Current PT practices often use artificial samples (reference materials, irradiated foods), raising concerns about their suitability compared to routine food samples.
• The commutability, or equivalence, of results between artificial and authentic samples is not well-established and can impact method evaluation.

Purpose of the Study:

• To conduct the first assessment of sample commutability in food microbiology proficiency testing.
• To evaluate the suitability of different PT sample types for accurately assessing laboratory performance.
• To identify potential issues arising from the use of artificial versus authentic food samples in PT.

Main Methods:

• Organized 13 food microbiology PTs with 10-28 participating laboratories.
• Utilized three types of PT items: genuine food samples, sterile food samples, and reference materials.
• Assessed commutability by comparing result distributions from natural and artificial PT samples, focusing on matrix effects.

Main Results:

• Matrix-correlated issues were observed when using non-food matrices like reference materials.
• Artificially inoculated food samples demonstrated fewer commutability issues compared to reference materials.
• The type of PT item significantly influenced the comparability of results.

Conclusions:

• Authentic or artificially inoculated food samples are essential for accurate performance evaluation in food microbiology PT.
• Conveniently used reference materials can introduce commutability problems, potentially leading to incorrect conclusions about method performance.
• Sample matrix effects are a critical factor in PT, highlighting the need for commutable samples to ensure reliable laboratory assessments.