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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
9
|
| pubmed:dateCreated |
1997-12-9
|
| pubmed:abstractText |
Changes in serum total and ionized magnesium (Mg and Mg2+) and calcium (Ca and Ca2+) were monitored in three patients who transiently developed severe (total Mg < 0.50 mmol/l) to profound hypomagnesemia (total Mg < 0.35 mmol/l) due to cisplatin or interleukin-2 therapies. Mg2+ and Ca2+ were measured with the Nova ion-selective electrodes at 37 degrees C and all results were normalized to pH 7.40. Independent of the etiology, the Mg2+ fraction (Mg2+/total Mg) increased as the concentration of the serum total Mg decreased in all three patients. When the total Mg was around or below 0.35 mmol/l the Mg2+ approached or exceeded total Mg, suggesting an error in the measurement of Mg2+. The findings were extended by including a group of 31 additional patients whose serum total Mg, Mg2+, total Ca, and Ca2+ concentrations varied from abnormally low to above normal. The serum total and ionized concentrations strongly correlated for both Mg (r2 = 0.88) and Ca (r2 = 0.92). The Mg2+ fraction rapidly increased with a fall in the total Mg concentration (r2 = 0.76) and total Mg/total Ca ratio (r2 = 0.71). In fact, with decreasing total Mg concentrations or total Mg/total Ca ratios, the Mg2+ fraction progressively increased to 93-128% of the total, confirming an error in the Mg2+ determinations. The Ca2+ fraction showed a slight and insignificant decrease with falling total Ca concentrations and total Mg/total Ca ratios. The Mg2+ concentration was directly related (r2 = 0.62), whereas the Ca2+ concentration showed a complex relationship to the total Mg/total Ca ratio. Whether this latter relationship represents a technical artifact or a true biological phenomenon requires further study. The apparent overestimation of Mg2+ at very low total Mg concentrations, and in the presence of a very low total Mg/total Ca ratio, could be due to improper chemometric correction of the Ca effect on the Mg electrode, non-linearity, and inadequate calibration. Whatever the mechanism, the failure of this method to correctly measure very low serum Mg2+ concentrations in the sera of patients with severe hypomagnesemia, or likely in any patient with an unusually low total Mg/total Ca ratio, erodes its diagnostic usefulness.
|
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:month |
Sep
|
| pubmed:issn |
0939-4974
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:volume |
35
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
701-9
|
| pubmed:dateRevised |
2004-11-17
|
| pubmed:meshHeading |
pubmed-meshheading:9352233-Adult,
pubmed-meshheading:9352233-Calcium,
pubmed-meshheading:9352233-Calibration,
pubmed-meshheading:9352233-Female,
pubmed-meshheading:9352233-Humans,
pubmed-meshheading:9352233-Ion-Selective Electrodes,
pubmed-meshheading:9352233-Magnesium,
pubmed-meshheading:9352233-Magnesium Deficiency,
pubmed-meshheading:9352233-Male,
pubmed-meshheading:9352233-Middle Aged,
pubmed-meshheading:9352233-Osmolar Concentration,
pubmed-meshheading:9352233-Phosphates,
pubmed-meshheading:9352233-Regression Analysis,
pubmed-meshheading:9352233-Reproducibility of Results
|
| pubmed:year |
1997
|
| pubmed:articleTitle |
Falsely high ionized magnesium results by an ion-selective electrode method in severe hypomagnesemia.
|
| pubmed:affiliation |
Clinical Pathology Department, W. G. Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland, USA. gcsako@nih.gov
|
| pubmed:publicationType |
Journal Article,
Case Reports
|