Survival predictability of time-varying indicators of bone disease in maintenance hemodialysis patients.

Although renal osteodystrophy and vitamin D analogs may be related to survival in maintenance hemodialysis (MHD) patients, most studies have examined associations between baseline values and survival without accounting for variations in clinical and laboratory measures over time. We examined associations between survival and quarterly laboratory values and administered paricalcitol in a 2-year (July 2001-June 2003) cohort of 58,058 MHD patients from all DaVita dialysis clinics in USA using both time-dependent Cox models with repeated measures and fixed-covariate Cox models with only baseline values. Whereas hypercalcemia and hyperphosphatemia were robust predictors of higher death risk in all models, the association between serum calcium and mortality was different in time-varying models. Changes in baseline calcium and phosphorus values beyond the Kidney Disease Outcome Quality Initiative recommended targets were associated with increased mortality. Associations between high serum parathyroid hormone and increased death risk were masked by case-mix characteristics of MHD patients. Time-varying serum alkaline phosphatase had an incremental association with mortality. Administration of any dose of paricalcitol was associated with improved survival in time-varying models. Controlling for nutritional markers may introduce overadjustment bias owing to their strong collinearity with osteodystrophy surrogates. Whereas both time-dependent and fixed-covariate Cox models result in similar associations between osteodystrophy indicators and survival, subtle but potentially clinically relevant differences between the two models exist, probably because fixed models do not account for variations of osteodystrophy indices and changes in medication dose over time.

Thyrotoxic hypokalemic periodic paralysis: report of four cases in black American males.

Thyrotoxic periodic paralysis (TPP) is an unusual complication of a fairly common disease affecting mostly Asian males. In the United States, there have been several reports of TPP in different ethnic populations and it appears that the incidence is approximately one-tenth of that found in Asian countries. Only six reports of TPP in African-Americans could be found in the literature; however, we are reporting four cases diagnosed within a 13-year period at our institution. We conclude that TPP may occur more often in Blacks than previously suspected and should be considered when patients present with unexplained hypokalemia, muscular weakness and rhabdomyolysis. The epidemiology, clinical manifestations, pathophysiology, and treatment of TPP are reviewed.

Preparation of radiolabled tetracosa mono- and dienoic acid methyl esters from rat erythrocyte lipids by thin layer chromatography.

An easy method of obtaining pure fatty acid methyl esters (FAME) of tetracosa mono- and dienoic acids (24:1, 24:2) using thin layer chromatography (TLC) is described. The total lipids isolated from rat erythrocytes were treated with methanolic-NaOH. Sphingomyelin was unaffected by this treatment and was separated from FAME of glycerolipids and cholesterol by TLC. FAME of sphingomyelin were then prepared by acid methanolysis. These esters migrated into 2 distinct bands on TLC. The slow moving band contained FAME of 16:0, 16:1, 18:0, 18:1, 19:0 and 20:0 wheras the fast moving band contained FAME of 22:0, 23:0, 24:0, 24:1 and 24:2. After AgNO3-TLC, the FAME of the fast moving band separated into 3 species; esters of saturated acids, 24:1 and 24:2, respectively. With erythrocyte lipids of rats fed a fat-free diet and injected with 14C-18:1, this method yielded 14C-24:1. From rats injected with 14C-18:2 and maintained on a corn oil diet, 14C-24:2 was obtained.