Overestimation of the 25(OH)D Serum Concentration With the Automated IDS EIA Kit

We have recently observed an increasing number of patients presenting very high serum levels of 25-hydroxyvitamin D [25(OH)D] (> 150 ng/mL), which, in all cases, had been measuredwith the IDS EIA kit adapted on different open automated platforms. We performed a comparison between the IDS EIA kit adapted on two different open automated platforms and the DiaSorin RIA. We found a systematic bias (higher levels with the IDS EIA kit) for concentrations more than 50-60 ng/mL that was less obvious when the IDS EIA was used in its manual procedure. We thus suggest to use the IDS EIA kit in itsmanual procedure rather than to adapt it on an automated platform, and to interpret cautiously a 25(OH)D greater than 100 ng/mL with this kit. (C) 2011 American Society for Bone and Mineral Research.