AbstractThe recent COVID-19 pandemic highlighted the importance of rapid and reliable pathogen detection. In the field of plant health accurate and timely detection is a corner stone for successful pest control. Plant pests can be diagnosed with a variety of tests, which may be developed by commercial companies or research institutions. The reliability of diagnostic tests depends on the intended use of the tests, their performance characteristics and associated uncertainty obtained from validation studies and the experience of the laboratories. The performance characteristics of tests are obtained during a process called validation. Performance characteristics that are frequently used to characterise tests include: analytical sensitivity, analytical specificity (inclusivity and exclusivity), selectivity, repeatability and reproducibility. The validation process requires significant investment in terms of human and financial resources and can be conducted by a single diagnostic laboratory or through interlaboratory comparisons. The purpose of this book is to provide practical and technical guidance for the organisation of test performance studies (TPS), which are one type of interlaboratory comparison where the performance of (a) test(s) (is)are assessed by two or more laboratories. The major steps and challenges faced during the preparation, organisation and reporting of TPS are identified and can be used by organisers of future TPS not only in the field of plant pest detection, but also in other areas.