Diurnal variation and short-term pre-analytical stability of serum soluble -klotho in healthy volunteers: a pilot study

Aim To investigate the diurnal variability and pre-analytical stability of soluble -klotho in serum. Background Recent evidence suggests that the cleaved extracellular domain of the -klotho receptor, soluble -klotho, affects phosphate homeostasis, ion channel regulation and antifibrotic/antioxidant pathways. However, soluble -klotho measurements have yielded inconsistent results when related to renal function, markers of mineral metabolism and patient outcomes. Pre-analytical factors such as biological variation and analyte stability may affect the interpretation of soluble -klotho results but are yet to be formally assessed. Methods Clotted blood samples were collected from 10 healthy adult volunteers at three time-points during the day to assess diurnal change. Additional samples were collected and allowed to stand at room temperature for 30, 60 and 120min, prior to centrifugation and analysis to evaluate analyte stability. Serum soluble -klotho was measured using a validated commercial enzyme-linked immunosorbent assay. Results Delayed processing of samples had no significant effect on serum soluble -klotho concentrations over a 2-h period. Serum soluble -klotho concentrations remained stable over morning, midday and afternoon time-points in this pilot study. Conclusion Serum soluble -klotho demonstrates short-term pre-analytical stability and minimal diurnal variability in this pilot study. Larger studies are warranted to confirm these findings.