required sample size in vaccination-challenge experiments with infectious bronchitis virus, a meta-analysis

• Published in: Avian pathology 2013-02, Vol.42 (1), p.9-16
• Main Authors: de Wit, J. J, Boelm, G. J, van Gerwe, T. J. W. M, Swart, W. A. J. M
• Format: Article
• Language: English
• Subjects: adults; Age; Animal diseases; Animal welfare; Animals; Antibodies, Viral - analysis; Binomial Distribution; Bronchitis; Cell culture; Chickens; Cluster Analysis; Coronavirus Infections - prevention & control; Coronavirus Infections - veterinary; Coronavirus Infections - virology; Data processing; Female; Immunization; infectious bronchitis; Infectious bronchitis virus; Infectious bronchitis virus - immunology; Male; Meta-analysis; Netherlands; Organ culture; Organ Culture Techniques - statistics & numerical data; Organ Culture Techniques - veterinary; Poultry; Poultry Diseases - prevention & control; Poultry Diseases - virology; Reviews; Sample Size; Specific Pathogen-Free Organisms; Statistics; Trachea - immunology; Vaccination; Vaccination - veterinary; Viral Vaccines - immunology; Viruses; Workers
• ISSN: 1465-3338; 0307-9457; 1465-3338
• DOI: 10.1080/03079457.2012.751485

For statistical, animal welfare and financial reasons the choice of the number of chickens per group in experiments is important. This estimation, together with the number of tracheal organ cultures (TOCs) that need to be examined from each chicken in order to assess protection, should be based on the difference in level of protection that one would like to be able to detect (effect size), the expected variability of the results between and within the chickens, the desired confidence level and the power of the study. To obtain data that would facilitate this estimation, a meta-analysis was performed on the data from 18 infectious bronchitis virus (IBV) vaccination-challenge experiments performed at the Dutch Animal Health Service Deventer, the Netherlands (GD) in order to determine and quantify the source of variation in the mean level of protection of different groups. For the calculations, 137 groups of chickens were subdivided into 10 clusters based on age (young or adult), vaccination (none, homologous or heterologous), challenge (IBV or mock infected) and location of vaccination (isolator at GD or in the field). The results were used to estimate the required number of chickens per group for the different clusters using 2, 5 or 10 TOCs per chicken to be able to detect effect sizes of 6.25%, 12.5%, 25% and 50% between groups of chickens with 95% confidence (P