The use of laboratory tests in patients with mild cognitive impairment.

Cognitive decline in elderly people can be caused by a specific and treatable metabolic disorder, and the use of laboratory tests is recommended as part of the diagnostic workup of patients with dementia. Patients with mild cognitive impairment (MCI) are commonly investigated by a similar laboratory diagnostic workup, however it is not known whether this clinical practice is justified. In the present study, we compared the frequencies of laboratory abnormalities, and laboratory abnormalities relevant for cognitive impairment, in consecutive patients with MCI or dementia (all types) observed in a memory clinic setting. As much as 55.1% of patients with MCI and 60.0% of patients with dementia had at least one abnormal laboratory value (a non-significant difference). The most frequent abnormal analysis was the serum cholesterol, that was high in 28.8% of patients with MCI and in 20.4% of patients with dementia. It was possible to detect, both in patients with MCI (1.5% and in patients with dementia (3.5%, a non-significant difference), abnormal metabolic values, indicating poorly controlled diabetes, renal failure, hyponatremia, folate or vitamin B12 deficiency and hyperthyroidism, which correction led to clinical improvement. The majority (62.5% of these alterations were previously unknown. These findings give support to the use of the laboratory diagnostic workup of dementia in patients with mild cognitive impairment.