An international collaborative study on foot and mouth disease virus assay methods. 1. Virus infectivity and...

In a collaborative study sponsored by the European Commission for the Control of Foot and Mouth Disease, workers in 19 laboratories participated in the early phases (1, 2 and 4). All three phases were devoted to assessments of virus infectivity and the neutralizing activity of sera. Virus preparations and antisera distributed from one laboratory were tested either by 'in house' or suggested methods. Analyses of the results clearly showed that whilst 'within' laboratory variation in the results of replicate tests was low, there were significant differences in the results from various laboratories. By attempting to standardize test conditions with distributed materials, e.g. media and cells, etc., the 'between' laboratory variation was reduced.