Objective: Vitamin B12 has important functions in the body. Its deficiency results in hematological and neurological impairments. Unless the deficiency status treated on early stage this neurological degenerations become permanent. Some studies have shown that the vitamin B12 levels persist between reference ranges, even the deficiency occurs. In addition holotranscobalamin that is the active form of vitamin B12 has been shown that can lead to early diagnosis. We aimed to reveal the relation between them within the 100-300ng/L of total vitamin B12 levels by evaluating the holotranscobalamin.

Material and Method: Patients (n:449) were divided into two groups according to their levels of vitamin B12 levels: group 1 (<189 ng/L); group 2 (>189ng/L). We used cut-off values 189 ng/mL for vitamin B12 and 25,1 pmol/L for holotranscobalamin as deficiency indicators. Both analytes were measured by Chemiluminesans Microparticule Immunassay (CMIA) method. The relation between two vitamins was evaluated by Pearson corelation analysis method.

Results: There was a positive statistically significant correlation between vitamin B12 and holotranscobalamin in our groups. (r=0,491, p<0.001 and r=0,271, p<0.001, respectively). By the way it seems the relation power decreased while total vitamin B12 levels increased, especially in second group that in reference ranges Holotranscobalamin levels were below cut-off value in 31,4% patients.

Discussion: Its shown that total vitamin B12 measurement isn't enough to diagnose deficiency, esspecially in 100-300ng/L levels holotranscobalamin can assist for early diagnosis and lead to early treatment that protect clinical impairments.