MLTS 1453 - Exam 3: Ch. 7

What is a urinalysis microscopic exam based on?

physical and chemical results

What is included in the physical exam in urinalysis?

color and clarity

What is included in the chemical exam in urinalysis?

• blood

• protein

• nitrite

• leukocyte esterase

• possible glucose

When does CLSI recommend to perform microscopic screening?

• requested by the physician

• laboratory-specified population (geriatric, diabetic, dialysis pt, etc.)

• any abnormal physical or chemical result

What preparations are made on the specimen before for a microscopic examination?

• examine when fresh or preserved—RBCs, WBCs, casts disintegrate in dilute (hypotonic, alkaline urine

• refrigeration precipitates crystals (amorphous urates / phosphates)—can obscure other elements

• MSCC urine

• thoroughly mix specimen before loading slide

Before a microscopic examination, how should a midstream clean catch be graded?

• less contamination (epithelial cells)

• abundance of epithelial = contamination

• abundance of epithelial w/ a +LE or +nitrite = UTI

What should the urine specimen volume be for a microscopic examnination?

• centrifuge 10-15 mL urine (reagent strips fit into 12 mL)

• quantities <12 mL should be documented

• some labs correct for volume

How should a urine specimen be centrifuged for microscopic examnination?

• standardize speed and time of centrifugation should be consistent

• 5 min. at relative centrifugal force (RCF) of 400 is ideal

• cap all specimens

How should the sediment in urine be prepared for microscopic examination?

• volume of sediment examined: 0.5-1.0 mL

• sediment must be resuspended via gentle agitation

• vigorous agitation must be avoided

What does commercial systems control in urine specimen?

consistent volume of sediment

Glass Slide Method

• 20 µL

• 22 × 22 glass cover slip

• do not overflow cover slip (heavier elements (casts) flow outside)

Commercial Systems

• capped, calibrated centrifuge tubes

• decanting pipettes to control sediment volume

Slides in commercial systems provide what?

• control the amount of sediment examined

• produce consistent monolayer of sediment for examination

• provide calibrated grids for more consistent quantitation

When examining for sediment, what is the minimum power fields?

• 10 low (10x)

• 10 high (40x)

What is the low power field used for when examining for sediment?

casts, general composition

Explain the process of sediment examination when using low power.

• initial focusing w/ low power, reduced light

• focus on epithelial cell, not artifacts that are in a different place

• scan edges of coverslip for casts w/ glass slide method

What is the high power field used for when examining for sedimen?

identification of type of sediment

After microscopic examination, how should results be reported?

• consistent within laboratory

• casts: average/LPF

• RBCs, WBCs: average/HPF

• epithelial cells, crystals, etc., in semiquantitative terms: few, moderate, many; 1-4+; followed by /LPF or /HPF

Why would sediment appear in urine?

• cells and casts in various stages of development and degeneration

• distortion of cells and crystals by the chemical content of the specimen

• presence of inclusions in cells and casts

• contamination by artifacts

What does using a bright-field microscopy do for urine examination?

increase the visibility of sediment

What stains can be used to identify characteristics of cellular structures (nuclei, cytoplasm, inclusions, etc.)?

• lipid stain

• gram stain

• prussian blue stain

• hansel stain

• acetic acid

Lipid Stains

• result in the appearance of free fat droplets and lipid-containing cells and casts in the sediment

• oil red O and sudan III stains used

• triglycerides and neutral fats = orange-red

• capable of polarizaiton

• cholesterol crystals do not stain

Gram Stain

• used primarily for the differentiation b/w gram-pos. (blue) and gram-neg. (red) bacteria

• identification of bacterial casts

Prussian Blue Stain

• hemosiderin granules seen w/ hemoglobinuria

• used for iron, stains the hemosiderin granules blue

Hansel Stain

• polynuclear WBCs are almost always neutrophils associated w/ microbial infection

• preferred stain for urinary eosinophils

• consists of methylene blue and eosin Y in methanol

Acetic Acid

• acidic acid will enhance WBC and epithelial cells

• RBCs lysed by acetic acid

• amorphous phosphate (commonly from refrigeration) crystals dissolves

Bright-Field Microscopy

• for examination of urine sediment can cause issues when the amount of light reaching specimen is not controlled

• sediment examination using a decreased light by adjusting rheostat on light source

• staining can increase visualization

Phase-Contrast Microscopy

• accomplished by adaptation of a bright-field microscope w/ a phase-contrast obj. lens and a matching condenser

• particularly advantageous for identifying low-refractive hyaline casts or mixed cellular casts and mucous threads

Polarizing Microscopy

• aids in the identification of crystals and lipids

• confirms the identificaiton nof