Multiple regression analyses for log-transformed factor VIII. For each model, the variables identified as making a significant contribution to the final model, once adjusted for the presence of other variables within the model, are presented. (Full model descriptive parameters are presented in online supplementary table 3.) Note that von Willebrand factor was only measured routinely for series 2, and therefore was not part of the series 1 model. There was no significant difference if transferrin saturation index was used instead of serum iron (data not shown). Higher order variables and interaction terms were not significant in either model. To enhance statistical power, we considered pooling the series, but this was not valid for these analyses, because in a combined stepwise regression model, the series indicator was significant.