Clinical investigation of the effect of blood sampling day on serum phosphorus concentration

: Whether the presence or absence of notification about the blood sampling date affects the serum phosphate concentration was examined. After periodical sampling at the beginning of the week with 2-day interval for regular dialysis, the blood was sampled on the midweek day with 1-day interval for dialysis upon the patient's consent right before sampling without an advance notification. In the next month subsequently periodical sampling at the beginning of the week and the sampling on the midweek day were performed after notification of the twice blood sampling before 1 week in advance. Then both serum phosphorus data were comparably investigated. In case the sampling was not notified, there is no difference in the serum concentration between the beginning of the week and the midweek day. On the other hand, in case the sampling was notified, the serum concentration significantly decreased on the weekday compared to that at the beginning of the week. It therefore was risky that the serum phosphorus concentration at the beginning of the week with 2-day interval for dialysis was presumed to be higher value than that on the midweek day with 1-day interval for dialysis. We need to consider the possibility that the presence or absence of notification about the blood sampling date affects the level of serum phosphorus concentration.