The routine procedure is based on the examination of concentrated urine sediment for the presence and quantity of red cells, white cells, crystals or casts, which are precipitins of the Tamm-Horsfall mucoprotein, secreted by the renal tubules, the clumping of cells or other material within a protein matrix. Formed in the renal tubules, these appear as molds, or “casts” of the renal tubule.
     A 12 mL volume of urine is placed into a conical centrifuge tube and centrifuged for 5 minutes at 1500 rpm (400 RCF Relative Centrifugal Force). With the exception of a one milliliter aliquot, the urine supernatant is decanted. The urine sediment pellet is resuspended in the one milliliter aliquot and a drop is placed on a microscope slide. A stain, such as Sternheimer-Malbin (KOVA Stain) permits easier viewing of the sediment. The urine sediment is first examined at 100x in order to identify and enumerate any casts present. The magnification is then increased to 400x for examination of cells, crystals and bacteria.
     Careful enumeration of red and white blood cells, casts and crystals (formed elements) is important in assessing the state of the patient. Use of glass slides and coverslips makes enumeration difficult. The volume of urine dropped on the slide, the tendency of the coverslip to float and for the formed elements to stream and concentrate at the edges are major sources of variation. When using the high power field (hpf) method of enumeration, these effects are difficult to manage. In contrast, use of chambered slides, such as a hemocytometer or the KOVA Glasstic™ Slide 10 eliminates much of this difficulty. Additional benefits of the hemocytometer are the counting grid in the focal plane of the cells, crystals and casts and the fixed volume capacity of the chamber. The grid provides a simple means of both defining the area being counted, to avoid duplication, and a mathematical tool for calculating the cells, crystals and casts per volume of urine. All of these features are offered by the Glasstic Slide 10 with grids with the added benefit of permitting up to ten samples to be viewed on a single, disposable slide.