Plasma calprotectin – preanalytical stability and interference from hemolysis

Abstract

As an activation product of neutrophil granulocytes, calprotectin has been widely used in fecal samples for diagnosis and monitoring of patients with inflammatory bowel disease. However, fecal sample collection is cumbersome, and pre-analytical sources of error are plentiful. Therefore, plasma calprotectin is being investigated as a promising new biomarker. To utilize any biomarker, pre-analytical factors such as stability and susceptibility to interference from hemolysis must be established. We present precision estimates, stability results as well as interference study on plasma calprotectin in EDTA-plasma using the Thermo Fischer Phadia 250 EliA^TM Calprotectin immunoassay. Precision was estimated by the use of patient pools as well as internal quality controls provided by the manufacturer. Coefficients of variance were below 6.9% for patient samples. Calprotectin was stable in EDTA plasma after storage at 5–8 °C for up to 4 days, as well as after long-term storage at −20 °C. Susceptibility to interference from hemolysis was high, especially for low concentrations of calprotectin (<50 ng/mL) where hemoglobin levels above 0.02 mmol/L lead to false increase in calprotectin concentrations of up to 100%.

Keywords:

• Stability
• plasma calprotectin
• preanalytical
• EDTA-plasma

Acknowledgments

The authors acknowledge the invaluable contributions by Charlotte Nørby Pedersen and laboratory technicians Laura Højbak Munk, Peter Skouboe and Gitte Paulsen.

Disclosure statement

A. B. B. has received speaker fee from Thermo Fisher Scientific. The authors declare no conflict of interest.

Additional information

Funding

This study was supported by the Department of Clinical Biochemistry, Aarhus University Hospital, Central Denmark Region. Thermo Fisher Scientific provided calprotectin kits free of charge for this study [Agreement no. 2021-731-16070]