To better understand these findings we undertook a number of joint modeling analyses aiming to ascertain whether reuse a) affected the exposure to middle molecules (β2M concentration) b) whether the association of a given β2M concentration with survival differed according to the extent of dialyzer reuse and c) whether the apparent attenuation of the protective effect of HF dialysis reflected worse outcomes with reused high flux membranes or improved survival in patients exposed to reused LF dialyzers. This evidence concerns the gene B2M and hydrops fetalis.