Effect of peroral AA-calcium on whole blood ionized calcium levels in patients with hypoparathyroidism. A dose-finding pilot study

Abstract We measured ionized calcium concentrations in whole blood from 91 patients who had no clinical or biochemical evidence of disturbed calcium homeostasis and who had a wide range of serum albumin concentrations. We used both a standard Ciba-Corning 634 analyzer, which has a membrane-restricted saturated KCl reference electrode bridge, and a modified instrument with a 150 mmol/L NaCl bridge. After adjusting the externally standardized values from each instrument for their least-squares regressions on pH, there was a significant correlation between ionized calcium and albumin only with the standard analyzer. In contrast, only values from the modified instrument correlated with serum chloride; this was not explained by ionic strength or organic anion interferences. We conclude that there is unlikely to be any major advantage in using a membrane-restricted isotonic NaCl reference electrode for in vitro clinical measurements, although it may be of value for in vivo monitoring. The importance of measuring serum albumin when using most commercial ionized calcium analyzers is emphasized.

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Effect of storage on measurement of ionized calcium in serum of uremic patients.

Clinical Chemistry ◽

10.1093/clinchem/31.2.287 ◽

1985 ◽

Vol 31 (2) ◽

pp. 287-289 ◽

Cited By ~ 14

Author(s):

N I Nikolakakis ◽

A M De Francisco ◽

R S Rodger ◽

E Gaiger ◽

T H Goodship ◽

...

Keyword(s):

Whole Blood ◽

Room Temperature ◽

Ionized Calcium ◽

Measured Concentration ◽

Analytical Variance ◽

Serum Ionized Calcium ◽

Uremic Patients ◽

Serum Storage

Abstract We studied, in 70 acidotic and non-acidotic uremic patients, the analytical variance in serum ionized calcium as related to duration and temperature of storage. Storage of serum or whole blood at 4 degrees C for as long as 6 h did not significantly alter the measured concentration of ionized calcium in the serum. Storage at room temperature for 6 h, or longer at 4 degrees C or -20 degrees C, resulted in inaccuracies in 39 to 79% of the samples of serum and in 38 to 92% of the samples of whole blood. These errors were not negated by correcting the values for ionized calcium to a pH of 7.40. Indeed, corrected values for calcium were even more unreliable in acidotic patients. We conclude that samples from uremic patients should be analyzed for ionized calcium within 2 h, or within 6 h if stored at 4 degrees C.

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Dry electrolyte-balanced heparinized syringes evaluated for determining ionized calcium and other electrolytes in whole blood

Clinical Chemistry ◽

10.1093/clinchem/37.10.1730 ◽

1991 ◽

Vol 37 (10) ◽

pp. 1730-1733 ◽

Cited By ~ 25

Author(s):

J Toffaletti ◽

P Ernst ◽

P Hunt ◽

B Abrams

Keyword(s):

Whole Blood ◽

Cellular Metabolism ◽

Ionized Calcium ◽

Blood Collection ◽

Heparin Concentration ◽

Incomplete Filling ◽

Blood Collection Tubes

Abstract By analyzing whole blood containing no anticoagulants (uncoagulated whole blood) immediately after collection, we evaluated the relative changes in the concentrations of ionized calcium and other electrolytes in whole blood collected in dry heparinized syringes and in serum prepared from blood collected in evacuated blood-collection tubes. Using these dry heparinized syringes, we collected and analyzed whole blood that contained either 33 or 13 int. units of lithium heparin or 40 int. units of electrolyte-balanced heparin per milliliter of blood. We evaluated the effects both of these heparins at different concentrations of ionized calcium and of the incomplete filling of the syringes. We conclude that: (a) when analyzed within 2-3 min after collection, uncoagulated whole blood provides ionized calcium results unaffected by anticoagulants or cellular metabolism; (b) the preparation of serum unpredictably changes ionized calcium; (c) the use of dry electrolyte-balanced heparin virtually eliminates the interference in ionized calcium concentrations between 0.9 and 1.6 mmol/L; and (d) incomplete filling of electrolyte-balanced heparinized syringes produces no effect in syringes two-thirds full (60 int. units/mL heparin concentration) and a small effect in syringes one-third full (120 int. units/mL heparin).

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Critical analytical and clinical aspects of ionized calcium in neonates.

Clinical Chemistry ◽

10.1093/clinchem/35.10.2027 ◽

1989 ◽

Vol 35 (10) ◽

pp. 2027-2033 ◽

Cited By ~ 13

Author(s):

J Wandrup

Keyword(s):

Calcium Homeostasis ◽

Whole Blood ◽

Clinical Symptoms ◽

Maternal Blood ◽

Ionized Calcium ◽

Preterm Neonates ◽

Clinical Aspects ◽

Cross Sectional ◽

Significant Data ◽

Neonatal Hypocalcemia

Abstract Clinical diagnosis in neonates is often based primarily on biochemical data, because clinical symptoms are difficult to assess and inconclusive. A knowledge of the validity of the data would therefore seem very important. Practical technical assessments lead me to conclude that measurement of ionized calcium at actual pH in anaerobic capillary samples of whole blood, currently practicable, is an easy and optimal laboratory analysis when biologically significant data are required for assessment of acute disturbances in calcium homeostasis of neonates. Values are given for ionized calcium, describing the relations in cord and maternal blood in uncomplicated pregnancies at term. Recent published cross-sectional and longitudinal reference values for ionized calcium, measured during the first weeks in healthy full-term and preterm neonates, seem to provide a new basis for the diagnosis and management of early neonatal hypocalcemia.

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