Reproducibility of monoamine metabolite measurements in human cerebrospinal fluid

The levels of homovanillic acid (HVA), 5-hydroxy indolacetic acid (5HIAA), and 3-methoxy-4-hydroxy phenylglycol (MHPG) were determined in the cerebrospinal fluid (CSF) of 28 patients with cognitive disorders on Day 1 and Days 8 or 15. During that period all patients were kept hospitalized under strict standard conditions, did not develop any acute CNS lesion, had no changes in their treatment and no acute systemic disease. The mean levels found in the first and second determinations were almost identical for the 3 metabolites; respectively 37.8 ng/ml and 36.3 ng/ml for HVA, 27.8 ng/ml and 27.9 ng/ml for 5HIAA, and 12.9 ng/ml and 12.3 ng/ml for MHPG. Thus, the mean values of these metabolites in CSF are reproducible at least during a 15-day hospitalization. However statistically significant individual changes in metabolite levels were found between the two samples in 82% of patients for HVA, 32% for HIAA and 48% for MHPG. The number of patients required to detect a significant change in the mean levels of each monoamine metabolite has been calculated taking into account the extent of intraindividual variations.