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In December 1992, Pennypacker et al1 reported that the true prevalence of Cbl deficiency in 152 elderly outpatients was at least 14.5%. These patients had elevated levels of serum MMA and/or homocysteine, which fell strikingly in every patient treated with Cbl.1
In June 1993, Norman and Morrison2 found that the prevalence of elevated urinary MMA levels varied from 3.0% to 5.1% in a cohort of 809 elderly individuals from various settings undergoing screening of MMA levels. They subsequently concluded that this value represented the true rate of Cbl deficiency.2
Pennypacker et al1 studied geriatric outpatients from a Veterans Affairs Medical Center and a university health science center, while Norman and Morrison2 studied elderly individuals from a health fair, eight retirement apartments, an assessment center, and a nursing home. Although all populations were elderly, the results were significantly different.
The group undergoing testing by Norman and
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