A Study in Total Vitamin D Assay

A renewed interest in vitamin D reflects almost the high prevalence of vitamin D deficiency worldwide and the increased publication connecting its deficiency to other clinical conditions other than bone health [1]. Therefore, the combination of total vitamin D levels with other tests should be considered when studying certain clinical conditions such as bone diseases and diabetes mellitus [2]. In most assays underestimation of the vitamin levels observed even with the new measurement of total vitamin D (D3+ D2) assay [1,3]. Also reference range for the vitamin around 50 nmol/l was established that is increased as you reach the equator due to increased sun exposure [2]. Assay provided in our country uses 75 nmol/l as reference range, regardless the fact that different assays will produce different results. We studied total vitamin D using two different assays (Roche and diaSorin).