The aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed.

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This cross sectional study shows that low plasma 25OHD is a major risk factor for hyperparathyroidism and Looser's zones. In dialysis patients, we suggest that the plasma levels of 25OHD are maintained around the upper limit of the reference range of sunny countries.

Given comparable control of plasma calcium, phosphate and 25-OH vitamin D, PTH control is comparable in both strategies. Sevelamer does not induce greater vitamin D depletion than CaCO(3). The transient decrease of serum bicarbonate after discontinuation of CaCO(3) in the sevelamer group suggests a less optimal prevention of acidosis. The sevelamer-induced decrease in LDL cholesterol gives this drug a potential advantage in cardiovascular prevention.

The predictive value of three different RIAs of PTH for the diagnosis of the histological type of bone disease has been compared in 24 asymptomatic patients on chronic hemodialysis who had never been exposed to aluminum intoxication and who agreed to have a bone biopsy after double tetracycline labeling. The serum concentrations of PTH were measured using a two-site immunoradiometric assay for intact PTH(1-84) and region specific assays directed against the C-terminal (53-84) fragment or the midregion (44-68) of the molecule. The bone histomorphometric analysis showed that six patients had nonaluminic adynamic bone disease with low bone formation rate (BFR), eight had mild hyperparathyroidism characterized by increased bone resorption and normal BFR, nine had severe hyperparathyroidism with increased BFR, and only one had true osteomalacia with increased osteoid seam thickness. All PTH assays correlated with the various parameters of bone resorption and bone formation and were able to differentiate the histological type of bone disease only when groups of patients were considered. For classifying individual patients into severe hyperparathyroidism and adynamic bone disease groups, the intact PTH assay had the best predictive value with a sensitivity of 100% and a specificity of at least 70%. A nonaluminic adynamic bone disease was observed in more than 50% of the patients who had normal intact PTH levels (6/11). It is concluded that the intact PTH measurement is superior to C-terminal and midregion assays for the prediction of the histological type of bone disease in hemodialyzed patients and should be of considerable value to adapt their treatment in order to avoid the emergence of both severe hyperparathyroidism and adynamic bone disease. In the absence of aluminum intoxication it seems that maintaining intact PTH concentrations 1 to 1.5 times the upper limit of normal would correspond to the best bone histology.