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Vitamin B₁₂ deficiency occurs frequently, especially among the elderly. However, screening for vitamin B₁₂ deficiency is hampered by poor sensitivity of the existing total vitamin B₁₂ assay. Methylmalonic acid (MMA) is considered as the most representative indicator of metabolic vitamin B₁₂ deficiency and is used as such in this study. The aim of this study was to validate the clinical usefulness of holotranscobalamin (holoTC) as an initial screening assay for metabolic vitamin B₁₂ deficiency in a mixed patient population.

Three hundred and sixty blood samples were collected by five Dutch hospitals. Vitamin B₁₂ and holoTC in serum were measured (AxSYM; Abbott). MMA in serum was measured by tandem mass spectrometry (LC-MS/MS).

Receiver operating curve (ROC) analysis demonstrated a greater area under the curve (AUC) for holoTC than for vitamin B₁₂ in detecting vitamin B …