Quantitative analysis of urine sediment using newly designed centrifuge tubes.

We quantified the formed elements of urine sediment using newly designed plastic centrifuge tubes with top and bottom openings and a 0.5 ml sized bottom ball (YZ tube). This design minimizes the adherence of formed elements that occurs on the glass surface of conventional tubes. The numbers of white blood cells (WBC) and red blood cells (RBC) using glass tubes did not differ from those observed using YZ tubes. However, the YZ tube method detected renal casts more frequently than the conventional glass tube method; the detection rate for renal casts in normal urine samples was 21.4% vs 2.9%, in samples from hospitalized patients it was 47.5% vs 10.2%, and from patients with kidney disease it was 88.9% vs. 44.4%. Especially, the YZ tube method detected more hyaline casts in all types of samples. The correlation between the glass tube and YZ tube methods was good for WBC (r=0.996), RBC (r=0.964), and epithelial cell count (r=0.939), but the correlation was weak for casts (r=0.511 for hyaline casts; r=0.359 for other casts). In conclusion, the YZ tube method of urine sediment analyses is an easy and accurate quantitative method; it is recommended as the method of choice for detecting and quantifying pathological casts in urine.