The purpose of a new study published in American Journal of Human Biology was to describe the validation of a commercial ELISA assay to measure osteocalcin—a biomarker of bone formation—from dried blood spots (DBS).

This study entailed the validation of the Osteocalcin Human Simple Step ELISA kit from Abcam (ab1951214) using 158 matched plasma and DBS samples. Limit of detection, analyte stability and specific forms of osteocalcin measured by the kit were also investigated.

The results revealed that:

• The mean plasma osteocalcin value was 218.2 ng/mL (range 64.6-618.1 ng/mL).
• Linear relationships existed between plasma and DBS concentrations of osteocalcin, with no apparent bias in plasma versus DBS concentrations.
• There was no apparent interference of the DBS matrix with measurement of osteocalcin in DBS.
• Intra-assay coefficient of variation (CV) for DBS was approximately 8% while average inter-assay CV was 14.8%. Limit of detection was 0.34 ng/mL.
• Furthermore, osteocalcin concentrations were stable in DBS stored at -28°C and room temperature, but not those stored at 37°C. This ELISA kit detected total osteocalcin.

The findings suggested that osteocalcin can be measured from DBS. Combined with a previously validated DBS assay for TRACP-5b—a bone resorption biomarker—these assays have the potential to shed light on and further clarify many factors contributing to bone strength.

Source: American Journal of Human Biology. 2020 Feb 4:e23394. doi: 10.1002/ajhb.23394.