What situations can cause erroneous results of a body fluid cell count when using an automated instrument, such as White Blood Cell (WBC) counts, bloody fluids, low cell counts, or interfering substances like lipemia?

Situations That Cause Erroneous Results in Automated Body Fluid Cell Counts

The most common situations that cause erroneous results of body fluid cell counts when using automated instruments include grossly bloody fluids, cell counts below 100/μL, large or clustered cells, highly viscous synovial fluids, and interfering substances like lipemia, hemolysis, or marked xanthochromia that affect hemoglobin measurement (options B and C are correct).

Common Causes of Erroneous Automated Body Fluid Cell Counts

Specimen-Related Factors

• Low Cell Counts (<100/μL)

  • Automated instruments have limited sensitivity at very low cell concentrations 1
  • Manual counting methods may be more reliable for specimens with cell counts below 100/μL 2

• Grossly Bloody Fluids

  • High RBC counts can interfere with accurate WBC enumeration 1
  • Blood contamination can lead to falsely elevated WBC counts 3

• Highly Viscous Samples

  • Synovial fluids with high viscosity may not flow properly through analyzer apertures 3
  • Can lead to inaccurate cell distribution and counting errors 1

• Large or Clustered Cells

  • Cell aggregates may be counted as single events, leading to falsely low counts 1
  • Clustered cells can block analyzer apertures or be misclassified 3

Interfering Substances

• Lipemia, Hemolysis, and Xanthochromia

  • These conditions interfere with optical measurements used for cell counting 4
  • Can affect light scatter patterns and fluorescence readings 5
  • May lead to inaccurate hemoglobin measurements that impact calculated parameters 4

• Presence of Non-Cellular Particles

  • Bacteria, yeast cells, and debris can be misidentified as WBCs 1
  • One study found significant discrepancies between automated and manual counts due to interfering factors such as bacteria and yeast cells 1

Impact on Different Body Fluids

Synovial Fluid

• False-positive automated WBC counts occur in 10.1% of total knee arthroplasty samples and 34.3% of total hip arthroplasty samples 3
• Presence of arthroplasty components substantially increases risk of false-positive automated counts 3

Cerebrospinal Fluid (CSF)

• Very low cell counts (common in CSF) are particularly challenging for automated analyzers 2
• Special protocols may be needed for accurate CSF cell counting 2

Peritoneal and Pleural Fluids

• Automated analyzers may provide reliable counts for initial screening but require scattergram inspection 1
• Interfering factors can lead to falsely elevated WBC counts 1

Best Practices to Minimize Erroneous Results

• Inspect scattergrams carefully when using automated analyzers 1
• Consider reflex manual counting for critical specimens, especially from arthroplasty sites 3
• Maintain proper instrument calibration and quality control 5
• Be aware of the lower limit of quantitation for your specific analyzer 1

When to Reject Specimens

• If blood is hemolyzed or frozen 6
• If clots are visible 6
• If the specimen is greater than 48 hours old 6

In conclusion, while automated cell counting offers efficiency and standardization for body fluid analysis, laboratories must be aware of these potential sources of error and implement appropriate protocols to ensure accurate results, particularly in challenging specimens.