An understanding of diurnal change is one of the important milestones for either biomarker validation or therapeutic level monitoring. The present study determines the most suitable period during the day for serum chondroitin sulfate WF6 (CS-WF6) and hyaluronic acid (HA) collection, and identifies the possible factors which affect the estimated putative half-life of serum CS-WF6 and hyaluronic acid (HA).
Forty-nine volunteers were enrolled in the present study, 22 healthy, 14 with anterior cruciate ligament (ACL) injury, and 13 volunteers with osteoarthritis (OA). Blood sample collection was carried out every four hours starting at 18.00 hours for 24 hours, with additional samples taken at 07:00 and 08:00 hours. Serum CS-WF6, HA levels were determined by an ELISA-based assay.
The serum CS-WF6 level was significantly different between the normal and both pathological conditions. The serum HA level was significantly different in every condition. There was no diurnal pattern of serum CS-WF6 and HA during the 24 hour period. An estimated putative half-life of serum CS-WF6 and HA was 4.32 ± 2.63 and 4.10 ± 2.34, respectively. The maximum CS-WF6, creatinine clearance (CrCl) level and body mass index (BMI) were not related to the changes of the WF6 half-life. The higher maximum HA and CrCl level related to the longer half-life of serum HA level, p = 0.008 and p = 0.001, respectively.
There was no diurnal pattern of serum CS-WF6 and HA due to the present study approach. Two hours after awakening in official time would be the suitable for serum CS-WF6. Two hours after awakening and after meals were suitable times for serum HA collection.