Quality control in the process of preparation for urinary sediment samples is
important for accurate diagnosis. In Japan, hematuria is defined as the presence of
occult blood and five or more red blood cells per high power field in urinary sediment
examination. The Japanese guidelines on urinary sediment examination procedures
state that a urine sample should be centrifuged for 5 minutes at 500×g in the
preparation process. Consequently, remaining components in the supernatant after
centrifugation, especially suspended red blood cells, have been reported. However,
changes in remaining red blood cells have not been investigated under different
centrifugal conditions. We have investigated the percentage of remaining red blood cells
in the supernatant, an issue in the guidelines on urinary sediment examination
procedures, using artificial hematuria.
Experiment 1: To investigate the percentage of remaining red blood cells with
different centrifugal forces, we prepared two types of artificial hematuria with pseudo -
urine made of saline and that made of 5% dextrose in acetated Ringer’s solution and
examined the percentage of remaining red blood cells in the supernatant after
centrifugation at 400 to 900×g. Although 3%-5% of the red blood cells remained at 500
×g specified by the standard guideline, the percentage decreased to 2.0% or less at 700
×g or higher.
xperiment 2: Regarding the percentage of remaining red blood cells at different
hours, the percentage was 6.87% for 5 minutes, 0.38% for 10 minutes, and 0.23% for 15
minutes at 500×g in artificial hematuria with pseudo-urine made of saline.
This study suggests that a certain percentage of red blood cells is suspended in the
supernatant by following the current Japanese guidelines on urinary sediment
examination procedures, which could affect the number of red blood cells in urinary
sediment examination.
標本の精度管理から考える尿沈渣検査の課題 －標本作製における相対的遠心力の影響－
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