Background Count on a Particle Counter
The "background count" on a particle counter is a measure of interference or particle impurities in diluent or sheath fluid (D).
Understanding Background Count in Laboratory Analysis
Background count is a critical measurement in particle analysis that represents contamination or interference present in the system before actual sample analysis. This measurement is essential for accurate results in both clinical and research laboratory settings.
Definition and Purpose
Background count serves several important functions:
- It quantifies the baseline level of particles present in the system that are not from the sample
- It allows for correction of actual sample results by subtracting this baseline contamination
- It verifies the cleanliness of the analytical system and reagents
- It ensures quality control in particle counting procedures
Sources of Background Count
Background counts typically originate from:
- Airborne microplastic particles or fibers 1
- Contaminants in diluent or sheath fluid used in the system
- Impurities in reagents or buffers
- Environmental contamination during sample handling
Importance in Laboratory Practice
Quality Control Measures
To minimize background count, laboratories implement several measures:
- Using clean air conditions (laminar flow cabinets or clean air laboratories) 1
- Covering samples when not being processed
- Wearing cotton lab coats to avoid synthetic fiber contamination
- Pre-rinsing and cleaning all materials and laboratory surfaces 1
Validation Through Controls
Two types of controls are essential for validating background count:
Negative controls (procedural blanks):
- At least three replicated blanks should be analyzed 1
- These quantify the variability of contamination
- Allow for correction of actual sample results
Positive controls:
- Verify recovery of particles during sample processing
- Assess losses that may occur during various steps of analysis 1
Clinical Implications
Accurate background count assessment is crucial for:
- Ensuring reliable cell counts in hematology analyzers
- Preventing false positive results in flow cytometry
- Maintaining accuracy in particle tracking analysis and resistive pulse sensing 1
- Validating results in research applications involving extracellular vesicles 1
Common Pitfalls and Best Practices
Pitfalls to Avoid
- Failing to run sufficient procedural blanks
- Not correcting sample results for background contamination
- Overlooking environmental sources of contamination
- Using inappropriate materials that may introduce particles
Best Practices
- Implement standardized protocols for background count assessment
- Regularly monitor and document background counts
- Ensure proper cleaning of all equipment and reagents
- Use appropriate negative controls to quantify contamination levels 1
- Report background count values alongside sample results for transparency
By understanding and properly accounting for background count, laboratories can ensure accurate and reliable particle analysis results, which is essential for both clinical diagnostics and research applications.