Hemoglobin variability and mortality in ESRD

Hemoglobin levels vary substantially over time in hemodialysis patients, and this variability may portend poor outcomes. For a given patient, hemoglobin concentration over time can be described by absolute levels, rate of change, or by the difference between observed level and expected level based on the preceding trend (i.e., seemingly random variability). We investigated the independent associations of these different methods of describing hemoglobin over time with mortality in a retrospective cohort of 34,963 hemodialysis patients. Hemoglobin concentration over time was modeled with linear regression for each subject, and the model was then used to define the subject's absolute level of hemoglobin (intercept), temporal trend in hemoglobin (slope), and hemoglobin variability (residual standard deviation). Survival analyses indicated that each 1g/dl increase in the residual standard deviation was associated with a 33% increase in rate of death, even after adjusting for multiple covariates. Patient characteristics accounted for very little of the variation in our hemoglobin variability metric (R2 = 0.019). We conclude that greater hemoglobin variability is independently associated with higher mortality.

Hypophosphatemia: clinical consequences and management

Current evidence regarding the clinical consequences of hypophosphatemia is not straightforward. Given the potentially different implications of hypophosphatemia among various patient groups, this commentary touches on patients with low serum phosphate after acute hospitalization, those with chronic ambulatory hypophosphatemia, and those with hypophosphatemia in the setting of advanced renal disease. Finally, this commentary examines the evidence regarding how best to replete phosphorous in the hypophosphatemic patient.

Cobalamin C deficiency complicated by an atypical glomerulopathy

Cobalamin C (cbl C) deficiency, an inherited disorder of vitamin B12 metabolism, causes elevated levels of methylmalonic acid and homocysteine and decreased methionine in all body fluids. Renal complications of cbl C disease are thrombotic microangiopathy (TMA), chronic renal failure, tubulointerstitial nephritis and proximal renal tubular acidosis. There is, however, only one case report of primary glomerular pathology, focal segmental glomerulosclerosis, in a cbl C deficient patient. We report a case of an atypical glomerulopathy in a 16-year-old male patient with cbl C deficiency. The glomerulopathy manifested with proteinuria and progressive renal insufficiency. The renal histologic, immunofluorescent and ultrastructural findings were similar, but not identical, to idiopathic membranoproliferative glomerulonephritis (MPGN) but also overlapped with those of a TMA. The serum complement profile was normal; there were scanty glomerular deposits of C3, no deposits of IgG and ultrastructural findings that were similar to those seen in either MPGN type III or a TMA. On the basis of these findings we have designated the renal disease as an atypical glomerulopathy.