undiagnosed vitamin B12 deficiency is remarkably common in the aged, but no specific risk group for screening can be identified. Thus, biochemical screening of unselected aged population is justified. General practitioners play a key role in diagnosing early vitamin B12 deficiency.

Objective: To study undiagnosed diseases in older people with and without dementia. Design: Cross-sectional population-based study in Lieto, southwestern Finland. Participants: All the inhabitants aged 64 and more in Lieto. Participation rate was 82% (n = 1,260). Measurements: Dementia and its subtypes were diagnosed according to prevailing criteria. Medical conditions were assessed in clinical examinations and from medical records. Results: 112 patients with dementia were found; 66% of them had at least 1 undiagnosed disease compared to 48% of the non-demented group (p = 0.041). The demented subjects had more undiagnosed hypercholesterolaemia (p = 0.039) and undiagnosed hypothyroidism (p = 0.032) than the controls. Conclusion: Undiagnosing is more common among patients with dementia. Screening strategies should be developed further to find these patients.

Results:The intra-and between-assay imprecision (CV) for the holoTC RIA were 4 -7% and 6 -8%, respectively. A 95% central reference interval for serum holoTC was 37-171 pmol/L. All participants (n ‫؍‬ 16) with probable Cbl deficiency, 86% of those with possible, and 30% of those with potential Cbl deficiency had holoTC below the reference limit (<37 pmol/L). The holoTC correlated

Either total vitamin B(12) or holotranscobalamin rather than homocysteine or methylmalonic acid should be used when screening an aged population prone to renal impairment.