Which sequence correctly describes how to prepare urinary sediment?

• A. fill conical tube with urine sample; centrifuge urine at 1,500 rpm for 3-5 mins; pour off supernatant; re-suspend sediment; tap or pipette onto slide; scan on 10x, examine on 40x, condenser down, low light
• B. fill conical tube with urine sample; pour off supernatant; centrifuge urine at 1,500 rpm for 3-5 mins; tap or pipette onto slide; re-suspend sediment; scan on 10x, examine on 40x, condenser down, low light
• C. centrifuge urine first; fill conical tube with urine sample; re-suspend sediment; pour off supernatant; tap onto slide; scan on 10x
• D. fill conical tube with urine sample; centrifuge at 2,000 rpm for 5 mins; re-suspend sediment; pour off supernatant; tap onto slide; scan on 4x

Answer: (A)

The key idea is to concentrate the sediment so you can see what’s inside. You do this by spinning the urine so the solid material forms a pellet, then removing the liquid and making a small, even smear of the sediment on a slide for microscopic examination. First, fill the tube with urine and centrifuge it for a few minutes at about 1,500 rpm to collect the sediment. After spinning, pour off the liquid carefully, leaving the pellet intact. Gently resuspend the sediment in a small amount of liquid so it becomes a uniform suspension that can be spread on the slide. Then place a drop on the slide and create a thin film for viewing. Start your search at low power (10x) to locate the material, then switch to higher power (40x) for detailed observation, with the condenser lowered and light kept low to improve contrast.

This approach explains why the correct sequence works: centrifuge to form a pellet, remove the supernatant, resuspend the sediment, mount on the slide, and examine first at 10x then at 40x with appropriate lighting. Sequences that omit centrifugation, discard supernatant before spinning, use inappropriate speeds, or begin at too low a magnification won’t yield a representative, easily visualized sediment.