Serum calprotectin levels in elderly males and females without bacterial or viral infections.

OBJECTIVES Calprotectin is released from activated leukocytes and calprotectin can thus be used as a marker for leukocyte activation. Faeces calprotectin is not only used as a marker for inflammatory bowel disease but can also be used to detect leukocyte activation in other body fluids. The aim of the present study was to study serum calprotectin levels in non-infected elderly individuals to establish reference intervals for the marker. METHODS Serum calprotectin was analyzed by immunoturbidimetry in 75 year old females and males without known infections. Individuals with CRP>20mg/L were excluded as this could indicate a subclinical infection. The calprotectin levels in the remaining 713 individuals were used to calculate reference values for this population. The Spearman rank correlations between calprotectin and 27 other laboratory biomarkers were also investigated. RESULTS There was a strong positive Spearman rank correlation between calprotectin and CRP (p<0.000001) and alkaline phosphatase (p<0.000001). There were also significant negative correlations between calprotectin and ApoA1 and direct HDL-cholesterol. CONCLUSIONS The reference interval for serum-calprotectin for all study subjects was 0.3-2.6 mg/L. Leukocyte alkaline phosphatase contributes to serum alkaline phosphatase levels.