Aim: Determining the stability of biomarkers continues to present challenges. Disease states, complex matrices and differences between recombinant and endogenous analytes require new approaches to maintain stability and measure it. In this report, we determine stability for two assays using trending and statistical analysis. Methodology & results: Monitoring trends helps identify out of specification measurements and determine whether concerns are due to the stability of the analyte. We also describe challenges presented when measuring arginase activity in human sputum, a complex matrix, for respiratory diseases. We controlled preanalytical protease activity and collection heterogeneity and monitored incurred sample stability to improve stability of arginine. Conclusion: These new approaches to achieving and determining biomarker stability may provide solutions for increasingly complex biomarker measurements.
Keywords: control charts; incurred sample stability; regulated bioanalysis; sputum.