An international collaborative study on foot and mouth disease virus assay methods. 2. Quantification of 146S particles.

Workers in 11 laboratories in Europe and one in North America participated in a collaborative study to assess the variability of a sucrose gradient procedure used for the quantification of foot and mouth disease virus (FMDV). To this end, a range of standards was distributed from one of the participating laboratories. A series of adenine preparations were used to assess the various spectrophotometers/UV monitors and it showed most to be accurate and linear in their responses. The FMDV and MS2 ribophage standards were used to assess the sucrose gradient procedure and indicated low levels of within laboratory variation whereas between laboratory variation was greater. Recalculation of results from the unprocessed data in the coordinating laboratory permitted the identification and reduction of one source of between laboratory variation. Despite the observed variations, the results indicated that meaningful comparisons could be made between the data of different laboratories provided that a procedure similar to the one described in this report is used.