Standardized counting of circulating platelet microparticles using currently available flow cytometers and...

Area of Science:

• Biotechnology
• Analytical Chemistry
• Clinical Diagnostics

Background:

• Standardization of microparticle (MP) quantification via flow cytometry is hindered by a lack of universal protocols.
• Previous methods relied on forward scatter (FSC)-based thresholds with 0.5 µm or 0.3 µm beads, limiting instrument compatibility.
• Sub-optimal FSC performance in some flow cytometers necessitates alternative detection strategies.

Purpose of the Study:

• To develop a standardized flow cytometry protocol for reproducible microparticle (MP) quantification in plasma.
• To establish an alternative side scatter (SSC)-based detection method compatible with a wider range of flow cytometers.
• To reconcile FSC- and SSC-based gating strategies for enhanced inter-instrument standardization.

Main Methods:

• Utilized reference beads of varying sizes (0.17–0.6 µm equivalent) for side scatter (SSC) threshold setting.
• Compared SSC-based MP gating with established forward scatter (FSC)-based methods.
• Evaluated MP counts on flow cytometers with varying FSC capabilities and SSC resolution.

Main Results:

• Flow cytometers with lower FSC resolution often exhibit superior SSC resolution and background rejection.
• An SSC-based gating strategy using 0.17–0.6 µm equivalent beads yields comparable MP counts to the FSC-based 0.3–1 µm equivalent method.
• The proposed SSC method provides reproducible PMP counts, independent of FSC signal quality.

Conclusions:

• A novel SSC-based standardization protocol enables accurate MP quantification across diverse flow cytometer platforms.
• This dual approach (FSC and SSC) addresses instrument variability and facilitates multicenter studies.
• The use of precisely sized reference beads is critical for achieving standardization in MP counting.