β2-Microglobulin is small 11.8 kDa protein presents on the surface of all nucleated cell in the human body, it forms part of the non-variable chain of Major Histocompatibility Complex class I. β2-Microglobulin production is constant and it is continuously released into the bloodstream. Its production increases during active infections, inflammation or blood cancers. The Kidneys are the main route of its elimination. It accumulates in patients with kidney disease and levels can rise significantly in patients with end-stage renal failure. Studies have shown that its accumulation in dialysis patients contributes to dialysis-related amyloidosis.

Haemodialysis is a significant contributor to removal of β2-microglobulin in those on dialysis. It removes β2-microglobulin from the blood rather than directly from tissues. Blood levels fall during dialysis. However, after haemodialysis, β2-microglobulin gradually moves from tissues into the bloodstream until equilibrium is reached (post-dialysis rebound). Our own published data and unpublished data suggest this rebound occurs by two hours post-dialysis approximately but is significant in magnitude. β2-Microglobulin is increasingly recognized as an important marker of middle-molecule solute clearance.

The investigators plan to recruit thirty haemodialysis patients. During two dialysis sessions blood samples will be taken to measure β2-microglobulin. During the first session, samples will be taken pre-dialysis and at intervals during the session. Post-dialysis samples will be taken at 1 and 2 hour time points. The investigators will perform a physical examination, fluid/nutrition assessment. Dialysis prescription and routine monthly blood and urine results will also be recorded, and patients will be asked to complete questionnaires about dialysis symptoms, fatigue and post-dialysis recovery time. At the start of the next dialysis, one final β2-microglobulin sample will be taken.

β2-microglobulin removal may be a useful marker of dialysis quality. The investigators aim to develop a predictive model to estimate the equilibrated β2-microglobulin to allow its dialysis clearance to be accurately assessed.