Limitations
The 25(OH)D results of the hospital admitted patients may not completely
compatible with the healthy population. Due to the retrospective design,
dietary habits of patients, food fortifications, taking vitamin D
supplements, or duration of sun exposure are not known. Lastly, two
different methodologies for 25(OH)D measurement was used, CLIA and HPLC.
The most valid method has been reported as HPLC, and measurements with
CLIA could result in lower values [34].