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P128 A new chemiluminescent immunoassay for measurement of Calprotectin in stool

A. Mandic Havelka*, M. Hörnfeldt, C. Palm Rosén

Karolinska University Hospital, Clinical Chemistry, Stockholm, Sweden

Background

The interest in calprotectin is constantly increasing due to its potential as a non-invasive, cheap and sensitive marker for intestinal inflammation. Currently, calprotectin is measured with commercially available ELISA and EliA assays. At present, these Methods are time-consuming and used only in clinical laboratories. Determination of calprotectin in stool requires often manual and long pre-analytical processing of the fecal samples, which may lead to long turn-a-round time for the calprotectin Results. We have validated a new chemiluminescent immunoassay for determination of calprotectin in combination with fully automatic system for pre-analytical processing of fecal samples in order to improve efficiency and generate shorter turn-a-round time for the calprotectin Results.

Methods

A new chemiluminescent immunoassay assay (DiaSorin S.p.a.) for determination of calprotectin was validated on LIAISON XL Analyzer (DiaSorin S.p.a.). Pre-analytical processing of fecal samples was performed with a fully automated robotic system (SoniC, S2G Scandinavia), which perform weighing, homogenization and centrifugation of stool samples.

Results

Assay linearity was proven throughout the measuring range from 5 to 800 mg/kg. Samples with higher levels of calprotectin are automatically diluted and reanalyzed. Within-run CVs ranged from 3,8-4,7 %, for concentrations of 40- and 160 mg/kg and total CV was calculated to 5 %.

The LIAISON Calprotectin assay shows good precision between duplicates. 90 samples with the concentrations between 5 mg/kg and 5000 mg/kg were analyzed and CV was calculated to 2%. The assay was compared to the ELISA assay that is currently used in the laboratory (BÜHLMANN Laboratories AG). Results obtained with the chemiluminescent immunoassay showed lower values then Results obtained with ELISA (slope=1,8, R2 = 0,79, n=85 (conc. range 5- 5000 mg/kg), slope = 2,8, R2 = 0,81, n=66 (conc. range 5-300 mg/kg)).

Our laboratory yearly analyze 15 000 calprotectin samples. The turn-around-time for calprotectin Results could be significantly decreased, from 2-3 weeks to 2-3 days when using automatic system for processing of stool samples and new LIAISON Calprotectin assay for measurement of calprotectin in stool.

Conclusion

The chemiluminescent immunoassay for measurement of Calprotectin in stool was shown to be precise with proven linearity over the measuring range. The automation of both pre-analytical processing of stool samples and measurement of calprotectin concentration resulted in improved efficiency and significantly shorter turn-around-time for calprotectin Results.