Linearity of HA concentration measured by EIA and SRID Independent monovalent pooled harvest (MPH) preparations (n = 16) were assayed by EIA and SRID, and the concentration of HA antigen plotted against each other. Strains tested include: A/Uruguay/716/07 (cross), A/Brisbane/10/07 (square), A/Brisbane/59/07 (open circle), B/Brisbane/03/07 (triangle), B/Florida/04/06 (circle), A/Victoria/210/09 (open diamond) and B/Brisbane/60/08 (diamond). For EIA analysis of these MPHs, mAbs raised against A/Hiroshima/52/05, A/Hiroshima/52/05, A/Brisbane/59/07, B/Panama/45/90, B/Panama/45/90, A/Singapore/37/09 and B/Brisbane/60/08 were used (respectively). The R
2 was determined to be 0·957. Error bars represent ± 1 SD.