Uremic middle molecules: separation and quantitation

A chromatographic method for separating uremic middle molecules has been developed, based on a modification of the method of Fürst et al. to permit accurate and rapid (less than 3.5 hours) determination of UMM levels. Semiautomation of the equipment has also resulted in 3 analyses per 8-hr working day. Comparison of UMM results in patients on a carefully controlled study of long (mean 7.5 hr) versus short (mean 3.6 hr) hours of hemodialysis indicate that UMM levels are higher on short dialysis but only peaks 7ao, 7a, 7b, and 7c1 show significant but relatively unimpressive differences between the two regimens. UMM levels have also been obtained in long-term CAPD patients. Data show that UMM levels remain stable, over at least 12 months of CAPD and all UMM levels are lower than in hemodialysis patients. From analysis of generation rate data there is also an indication that UMMs may be dietary related.