What is urinalysis with automated (auto) and microscopic (w/scope) components?

Urinalysis, Auto w/Scope: A Comprehensive Diagnostic Tool

Urinalysis with automated and microscopic components (URINALYSIS, AUTO W/SCOPE) is a two-part diagnostic test that combines automated analysis of urine with microscopic examination, providing comprehensive evaluation of urine samples for detecting urinary tract infections, kidney disease, and other conditions affecting the urinary system.

Components of Urinalysis, Auto w/Scope

Automated Analysis

• Technology Used:

  • Image-based systems using flow imaging analysis technology and software to classify particles in uncentrifuged urine specimens 1
  • CMOS (complementary metal oxide semiconductor) technology for enhanced analytical sensitivity 2
  • Automated reflectometry for quantitative reading of urinary test strips 2

• Parameters Measured:

  • Physical characteristics: Color, clarity, specific gravity
  • Chemical analysis (dipstick):
    • Leukocyte esterase - indicates presence of white blood cells (94% sensitivity in clinically suspected UTI) 1
    • Nitrite - indicates presence of bacteria that convert nitrate to nitrite (highly specific but less sensitive) 1
    • pH, protein, glucose, ketones, bilirubin, urobilinogen, blood

Microscopic Examination (w/scope)

• Purpose: Visual confirmation and identification of cellular elements and other particles
• Elements Identified:
  • Red blood cells (RBCs) - regular or dysmorphic
  • White blood cells (WBCs)
  • Epithelial cells
  • Bacteria
  • Casts (hyaline, granular, cellular)
  • Crystals
  • Yeast
  • Other organisms or particles

Clinical Applications

Urinary Tract Infection Detection

• Automated urinalysis combined with microscopy has sensitivity of 82% and specificity of 92% for UTI detection 1
• Important considerations:
  • Negative urinalysis does not always exclude UTI in children under 2 years (10-50% of culture-positive UTIs can have negative urinalysis) 1
  • Combined leukocyte esterase and nitrite positivity has 96% specificity for UTI 1

Kidney Disease Evaluation

• Helps detect:
  • Glomerular bleeding (presence of dysmorphic RBCs)
  • Proteinuria
  • Casts (indicating kidney tubular damage)
  • Crystals (may indicate stone formation)

Diagnostic Algorithm

1. Automated analysis first:

   • Provides rapid screening of physical and chemical parameters
   • Quantifies cellular elements through flow cytometry or image-based analysis
   • Flags abnormal results

2. Microscopic review when indicated:

   • Performed when automated analysis shows abnormalities
   • Required for confirmation of certain elements like dysmorphic RBCs, casts, crystals 3
   • Essential for distinguishing true UTI from asymptomatic bacteriuria 1

Advantages Over Traditional Methods

• Standardization: Reduces variability in results compared to manual methods 4
• Quantitative reporting: Provides precise counts rather than semi-quantitative estimates 4
• Improved workflow: Higher throughput in clinical laboratories 2
• Enhanced sensitivity: Better detection of certain elements like casts and dysmorphic erythrocytes 4

Limitations and Pitfalls

• Auto-classification limitations: Less reliable for identifying yeast and bacterial cocci 4

• Need for manual review: Some specimens still require microscopic confirmation, particularly for:

  • Dysmorphic erythrocytes
  • Differentiation of cast types
  • Certain crystals
  • Trichomonas and oval fat bodies 3

• Sample handling considerations:

  • Specimens should be processed promptly or refrigerated to prevent bacterial overgrowth 1
  • Proper collection techniques are essential to avoid contamination

Interpretation Considerations

• Asymptomatic bacteriuria: Presence of bacteria without pyuria often indicates colonization rather than infection 1
• Dilution effects: Integration of dilution parameters (creatinine, specific gravity) improves result interpretation 2
• Culture correlation: For suspected UTI, culture remains the gold standard with interpretation based on colony counts:
  • ≥50,000 CFUs/mL of a single pathogen typically indicates significant bacteriuria in children 1
  • Collection method affects threshold for positive culture (catheterization vs. clean catch) 1

The automated and microscopic components of urinalysis complement each other, providing a comprehensive evaluation that balances efficiency with diagnostic accuracy. While automation has significantly improved standardization and workflow, microscopic review remains essential for certain clinical scenarios.