title: Erythrocyte magnesium in elderly patients: not a reliable guide to magnesium status.
abstract: To assess body magnesium status in various illness states in older people by measurement of serum magnesium (S Mg) and erythrocyte magnesium (E Mg) and to explore the limitations of E Mg measurement. S Mg and E Mg were measured in 150 consecutive out-patients, mean age 77 years, and in 100 consecutive in-patient admissions, mean age 80 years. Results were analysed for different diagnostic groups S Mg was normally distributed for both in-patients and out-patients, mean values 0.79 mmol/l and 0.77 mmol/l respectively. In-patient E Mg concentrations were often higher but the distribution was considerably skewed, median 2.28 mmol/l, mean 2.35 mmol/l. Out-patient E Mg concentration followed a near normal distribution, median 2.32 mmol/l, mean 2.30 mmol/l. There was a significant correlation between E Mg and S Mg for out-patients, R = 0.29 (p < 0.001). In-patients with infections and pressure sores had significantly raised E Mg concentrations but normal or low S Mg. High E Mg concentrations in illness are likely to be due to alterations in characteristics of the erythrocytes themselves rather than an indication of body magnesium excess. E Mg concentrations in illness should be interpreted with caution.
authors.affiliation: Department of Geriatric Medicine, Royal Infirmary, Glasgow, UK.
authors.forename: B J
authors.initials: BJ
authors.lastname: Martin
authors.forename: T D
authors.initials: TD
authors.lastname: Lyon
authors.forename: G S
authors.initials: GS
authors.lastname: Fell
authors.forename: P
authors.initials: P
authors.lastname: McKay
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000437:Alcoholism / Q000097:blood; D015415:Biomarkers / Q000097:blood; D002561:Cerebrovascular Disorders / Q000097:blood; D016001:Confidence Intervals; D004912:Erythrocytes / Q000737:chemistry*; D005260:Female; D006333:Heart Failure / Q000097:blood; D006801:Humans; D007297:Inpatients; D007592:Joint Diseases / Q000097:blood; D008274:Magnesium / Q000097:blood*; D008297:Male; D009752:Nutritional Status; D010045:Outpatients; D003668:Pressure Ulcer / Q000097:blood; D015203:Reproducibility of Results; D012141:Respiratory Tract Infections / Q000097:blood
chemical_list: D015415:Biomarkers; D008274:Magnesium