Plasma calprotectin - preanalytical stability and interference from hemolysis

Area of Science:

• Clinical Chemistry
• Biomarker Discovery
• Inflammatory Bowel Disease Diagnostics

Background:

• Calprotectin, an activation product of neutrophil granulocytes, is a validated biomarker for inflammatory bowel disease (IBD) using fecal samples.
• Fecal sample collection presents challenges, including cumbersome procedures and numerous pre-analytical errors, driving the need for alternative biomarkers.
• Plasma calprotectin is emerging as a potential alternative biomarker for IBD diagnosis and monitoring.

Purpose of the Study:

• To evaluate the pre-analytical stability and interference susceptibility of plasma calprotectin.
• To establish precision estimates for plasma calprotectin measurements.
• To assess the suitability of plasma calprotectin as a reliable biomarker in clinical settings.

Main Methods:

• Plasma calprotectin was analyzed using the Thermo Fischer Phadia 250 EliA™ Calprotectin immunoassay.
• Precision was determined using patient pools and manufacturer-provided quality controls.
• Stability was assessed after storage at 5-8°C and -20°C.
• Interference from hemolysis was studied at various hemoglobin concentrations.

Main Results:

• Coefficients of variance for plasma calprotectin were below 6.9% in patient samples, indicating good precision.
• Calprotectin demonstrated stability in EDTA plasma stored at 5-8°C for up to 4 days and long-term storage at -20°C.
• High susceptibility to hemolysis interference was observed, particularly at low calprotectin concentrations (<50 ng/mL).
• Hemoglobin levels above 0.02 mmol/L caused a false increase in calprotectin concentrations by up to 100%.

Conclusions:

• Plasma calprotectin is a stable biomarker in EDTA plasma under tested storage conditions.
• The significant interference from hemolysis, especially at low concentrations, poses a critical pre-analytical challenge.
• Careful consideration of sample handling to avoid hemolysis is essential for the accurate clinical application of plasma calprotectin as an IBD biomarker.