Serum-ionised magnesium in patients with acute myocardial infarction. Relation to cardiac arrhythmias, left ventricular function and mortality.

Measurement of serum-ionised magnesium has recently become available, and we report the first study of the relation of this parameter to arrhythmias, left ventricular function and mortality in patients with an acute myocardial infarction. Serum-ionised magnesium was determined in 217 consecutive patients admitted to hospital with an enzyme confirmed AMI. 70 healthy subjects acted as a control group. The main study parameters were occurrence of arrhythmias, left ventricular function estimated by echocardiography, and mortality after 10 months for the AMI patients. AMI patients had significantly lower serum-ionised magnesium compared to healthy controls but the level of serum-ionised magnesium in the acute phase of a MI was neither related to arrhythmias, left ventricular function nor mortality.

Short Report: Translation of Analysis Results between Serum Ferritin Assays, Ferritin RIA Amersham™ and Abbott AxSYM™ Ferritin.

The serum ferritin assays, Ferritin RIA Amersham™ and Abbott AxSYM™ Ferritin were compared in order to translate values from one assay to the other. Serum ferritin was analysed with both assays in 102 samples. Logarithmic transformation of the results was performed in order to stabilize the variance. The relationship between the untransformed values was most exactly expressed by a proportionality: AxSYM Ferritin = 0.873 * RIA Ferritin. Due to this proportionality, the numerical difference between the assays increases with the ferritin concentration, although the percentage difference between the assays remains constant.

Evaluation of an ionized magnesium-pH analyzer--NOVA 8.

An ion-selective analyzer (NOVA 8 [previously NOVA CRT], NOVA Biomedical Waltham, USA) for simultaneous measurement of the concentration of ionized magnesium (cMG2+) and pH is investigated for linearity and influence of calcium ions on the Mg2+ results in different Mg2+ aqueous solutions with/without added calcium. Within the cMg2+ range 0-3.0 mmol/L, which covers most clinical values, we found cMg2+ values close to the line of identity, with a sensitivity about 94%, but 0.09 mmol/L lower in the absence of Ca2+. The analytical precision (CV) for human serum control was 1.7% in the physiological range. The accuracy and precision data for the Mg2+ electrode meet the demands for reliable results within the range for clinical use. We found a reference interval (95%) for cMg2+ of between 0.43 and 0.59 mmol/L serum, with a mean value of 0.51 mmol/L for healthy adults in the non-fasting state with no relation to sex or age. The mean cMg2+ was 61% of the mean concentration of plasma total magnesium (cTMg) ranging from (95%) 49% to 73%. No significant correlation was found between cMg2+ and total protein, albumin, phosphate, Ca2+, and total CO2. No significant difference was found between mean values for cMg2+ in whole blood, plasma, and serum. Serum samples could be stored for 24 h at 4 degrees C without significant change. Storage at -20 degrees C for 7 months caused a mean cMg2+ decrease of 8.3%. The mean slope delta lgcMg2+/delta pH measured after equilibration with different pCO2 values in each serum sample from the reference population was -0.0110, indicating a close agreement between the values for actual cMg2+ and adjusted cMg2+ (pH = 7.4).

Calibration of Abbott AxSYM Ferritin kit using the WHO Human Liver Ferritin International Standard 80/602.

A commercial ferritin kit (Abbott AxSYM Ferritin) was calibrated using the WHO Human Liver Ferritin International Standard 80/602. The reconstituted WHO freeze-dried standard was diluted to obtain six concentration levels ranging from 10-840 micrograms/l. In the analysis of the data, logarithmic transformation of the results was performed in order to stabilize the variance. The AxSYM kit yielded slightly higher values than the WHO Ferritin Standard (p < 0.05). The relation between the AxSYM kit and the WHO Ferritin Standard (untransformed values) was described by a proportionality: FerritinAxSYM = 1.057 x FerritinWHO. WHO Ferritin Standard values of 12 and 15 micrograms/l (used as cut-off values for absent or small body iron reserves) yielded calculated AxSYM values of 12.7 and 15.9 micrograms/l. A WHO Ferritin Standard value of 30 micrograms/l (used threshold value for the presence of stainable bone marrow haemosiderin iron) yielded a calculated AxSYM value of 31.7 micrograms/l.

Calibration of the Amersham Ferritin RIA kit using the WHO human liver ferritin international standard 80/602.

A commercial ferritin kit (Amersham Ferritin RIA (A)) was calibrated using the WHO human liver ferritin international standard 80/602 (W). The reconstituted WHO freeze-dried standard was diluted to obtain five concentration levels ranging from 10-800 micrograms/l. Logarithmic transformation of the values was performed in order to stabilize the variance, yielding the regression equation: logA = 0.0235 + 1.0022 logW. The slope of the regression line (being very close to, and not significantly different from, one) was set to one, and the relation between the untransformed values then became a proportionality: A = 1.067 x W. A WHO standard ferritin value of 15 micrograms/l (often used as cut-off value for absent iron reserves) and of 30 mu/l (often used as threshold value for the presence of stainable marrow haemosiderin iron) yielded calculated Amersham Ferritin RIA values of 16.0 micrograms/l and 32.0 micrograms/l.

Statistical pitfalls in the comparison between two commercial serum ferritin kits, Pharmacia and Amersham.

Two commercial ferritin kits, Phadebas Ferritin PRIST (kit B) and Ferritin RIA Amersham (kit A) were compared in order to "translate" ferritin values from one kit to the other. Ferritin levels in 222 sera were determined with both kits in the concentration range 5-838 micrograms/l. Regression analysis disclosed a parabolic regression between the logarithmically transformed results obtained with the two kits. Measured kit B values of 10, 12, 15, 30 and 300 micrograms/l corresponded to calculated kit A values of 15, 17, 20, 34 and 321 micrograms/l, respectively. In kit A, storage of sera for two years at -25 degrees C in combination with freeze-thawing three times produced a minor fall (p < 0.0001) in ferritin levels with a median percent decline of 16%.

Venous muscle pump function during pregnancy. Assessment by ambulatory strain-gauge plethysmography.

The venous muscle pump function was quantitatively assessed through pregnancy weeks 16, 30, 38 and 3 months (week 53) following delivery, in 24 pregnant women who completed a normal pregnancy. A statistically significant increase was found in the mean venous reflux (P less than 0.01), which was restored to initial values postpartum. Expelled calf volume remained stable throughout pregnancy but increased following delivery. Venous outflow from the legs was significantly reduced in the third trimester. Subjective symptoms of venous insufficiency increased through pregnancy, but, these symptoms had virtually disappeared post partum, corresponding to the muscle pump normalization. No statistical correlation was found between venous muscle pump values and changes in hormone concentrations of estradiol, estriol and progesterone. It is suggested that venous insufficiency development in pregnancy is caused primarily by mechanical obstruction, or hormonal influence other than that of estradiol, estriol or progesterone. 17% (4.7-37%) of the women with a normal pregnancy developed a pathological venous muscle pump function.

[Ionized calcium, total calcium and albumin corrected calcium in the serum in 1213 patients with suspected calcium metabolic diseases. A prospective multicenter study]. / Ioniseret calcium, totalcalcium og albumin-korrigeret calcium i serum hos 1.213 patienter mistaenkt for calciummetabolisk sygdom. En prospektiv multicenterundersøgelse.

The correlation between serum ionized calcium, serum total calcium and albumin corrected total calcium was investigated in a prospective multicentre investigation of 1,213 patients with suspected calcium metabolic disease. 31.0% of the patients were misclassified when serum total calcium was measured instead of serum ionized calcium. The diagnostic discrepancy between the two methods decreased with the calculation of albumin corrected total calcium or calculated ionized calcium (17.9%). On justing for the analytical error connected with the measurement of ionized calcium, 11.2% of the patients were still misclassified. It is not possible precisely to predict serum ionized calcium from the measurement of serum total calcium and we recommend measurement of serum ionized calcium in patients believed to have calcium metabolic disease.

Comparison of serum total calcium, albumin-corrected total calcium, and ionized calcium in 1213 patients with suspected calcium disorders.

The correlations between serum ionized calcium, serum total calcium, total calcium corrected for albumin and calculated ionized calcium were investigated in a prospective multicentre investigation of 1213 patients suspected of having calcium metabolic disease. Diagnostic discordance between serum total calcium and measured ionized calcium was found in 31% of the patients. With the calculation of albumin-corrected total calcium or calculated ionized calcium the discordance decreased to 17.9%. The diagnostic discordance which could be ascribed to the analytical imprecision (CV = 1.5%) amounted to only 6.7%. Although we found highly significant correlations between the parameters, a considerable scatter around the regression line made prediction of ionized calcium from albumin-corrected total calcium unreliable in many patients.