Magnesium

Catalog Number: 20737593322

SYSTEM INFORMATION

For cobas c 311/501 analyzers:

MG: ACN 693 (serum and plasma)

MGU: ACN 695 (urine)

S-MG: ACN 770 (STAT, serum and plasma, reaction time: 3)

S-MGU: ACN 771 (STAT, urine, reaction time: 3)

For cobas c 502 analyzer:

MG2: ACN 8693 (serum and plasma)

MGU2: ACN 8695 (urine)

S-MG2: ACN 8770 (STAT, serum and plasma, reaction time: 3)

SMGU2: ACN 8771 (STAT, urine, reaction time: 3)

INTENDED USE

In vitro test for the quantitative determination of magnesium in human serum, plasma and urine on Roche/Hitachi cobas c systems.

STORAGE AND STABILITY

MG
Shelf life at 15-25 °C: See expiration date on cobas c pack label.
On-board in use and refrigerated on the analyzer: 12 weeks
Diluent NaCl 9 %
Shelf life at 2-8 °C: See expiration date on cobas c pack label.
On-board in use and refrigerated on the analyzer: 12 weeks

APPLICATION FOR SERUM AND PLASMA

cobas c 311 test definition
Assay type 2 Point End
Reaction time / Assay points 10 / 6-9 (STAT 3 / 6-9)
Wavelength (sub/main) 450/660 nm
Reaction direction Decrease
Units mmol/L (mg/dL, mval/L)
Reagent pipetting Diluent (H2O)
R1 160 µL 20 µL
R2 28 µL 30 µL
Sample volumes Sample Sample dilution
Sample Diluent (NaCl)
Normal 2 µL
Decreased 10 µL 15 µL 135 µL
Increased 4 µL

cobas c 501/502 test definition
Assay type 2 Point End
Reaction time / Assay points 10 / 10-15 (STAT 3 / 10-15)
Wavelength (sub/main) 450/660 nm
Reaction direction Decrease
Units mmol/L (mg/dL, mval/L)
Reagent pipetting Diluent (H2O)
R1 160 µL 20 µL
R2 28 µL 30 µL
Sample volumes Sample Sample dilution
Sample Diluent (NaCl)
Normal 2 µL
Decreased 10 µL 15 µL 135 µL
Increased 4 µL

CALIBRATION

Traceability: This method has been standardized against atomic absorption spectrometry.

For the USA, this method has been standardized against SRM 929 (IDMS).

Calibrators S1: H2OS2: C.f.a.s.
Calibration mode Linear
Calibration frequency 2-point calibrationafter reagent lot changeas required following quality control procedures

LIMITS AND RANGES

Measuring range

Serum/plasma

0.1-2.5 mmol/L (0.24-6.08 mg/dL)

Determine samples having higher concentrations via the rerun function. Dilution of samples via the rerun function is a 1:2 dilution. Results from samples diluted by the rerun function are automatically multiplied by a factor of 2.

Urine

0.5-12.5 mmol/L (1.22-30.4 mg/dL)

Determine samples having higher concentrations via the rerun function. Dilution of samples via the rerun function is a 1:2 dilution. Results from samples diluted by the rerun function are automatically multiplied by a factor of 2.

Lower limits of measurement

Lower detection limit of the test

Serum/plasma

0.1 mmol/L (0.24 mg/dL)

The lower detection limit represents the lowest measurable analyte level that can be distinguished from zero. It is calculated as the value lying three standard deviations above that of the lowest standard (standard

1 + 3 SD, repeatability, n = 21).

Urine

0.5 mmol/L (1.22 mg/dL)

The lower detection limit represents the lowest measurable analyte level that can be distinguished from zero. It is calculated as the value lying three standard deviations above that of the lowest standard (standard

1 + 3 SD, repeatability, n = 21).

SPECIFIC PERFORMANCE DATA

Representative performance data on the analyzers are given below. Results obtained in individual laboratories may differ.

PRECISION

Precision was determined using human samples and controls in an internal protocol. Serum/plasma: Repeatability* (n = 21), intermediate precision** (3 aliquots per run, 1 run per day, 21 days); Urine: Repeatability* (n = 21), intermediate precision** (3 aliquots per run, 1 run per day, 10 days). The following results were obtained:

Serum/plasma

Urine

Repeatability* Meanmmol/L (mg/dL) SDmmol/L (mg/dL) CV%
Precinorm U 1.00 (2.43) 0.01 (0.02) 1.5
Precipath U 1.62 (3.89) 0.01 (0.02) 0.7
Human serum 1 0.79 (1.92) 0.01 (0.02) 1.1
Human serum 2 1.65 (4.01) 0.01 (0.02) 0.7

Intermediate precision** Meanmmol/L (mg/dL) SDmmol/L (mg/dL) CV%
Precinorm U 0.929 (2.26) 0.008 (0.02) 1.5
Precipath U 1.55 (3.77) 0.01 (0.02) 0.7
Human serum 3 0.530 (1.29) 0.008 (0.02) 1.1
Human serum 4 1.64 (3.99) 0.01 (0.02) 0.6

Repeatability* Meanmmol/L (mg/dL) SDmmol/L (mg/dL) CV%
Control level 1 2.68 (6.51) 0.02 (0.05) 0.8
Control level 2 5.57 (13.5) 0.03 (0.1) 0.6
Human urine 1 0.621 (1.51) 0.008 (0.02) 1.2
Human urine 2 4.74 (11.5) 0.04 (0.1) 0.8

Intermediate precision** Meanmmol/L (mg/dL) SDmmol/L (mg/dL) CV%
Control level 1 2.09 (5.08) 0.03 (0.07) 1.4
Control level 2 4.73 (11.5) 0.04 (0.1) 0.8
Human urine 3 1.41 (3.43) 0.05 (0.12) 3.9
Human urine 4 11.5 (27.9) 0.05 (0.12) 0.4
* repeatability = within-run precision
** intermediate precision = total precision / between run precision / between day precision

METHOD COMPARISON

Magnesium values for human serum/plasma and urine samples obtained on a Roche/Hitachi cobas c 501 analyzer (y) were compared with those determined using the same reagent on a Roche/Hitachi 917 analyzer (x).

Serum/plasma

Sample size (n) = 217

Urine

Sample size (n) = 172

Passing/Bablok11 Linear regression
y = 1.000x + 0.052 mmol/L y = 1.008x + 0.044 mmol/L
t = 0.922 r = 0.998
The sample concentrations were between 0.530 and 1.94 mmol/L (1.29 and 4.71 mg/dL).

Passing/Bablok11 Linear regression
y = 1.003x - 0.040 mmol/L y = 1.004x - 0.023 mmol/L
t = 0.959 r = 0.999
The sample concentrations were between 0.500 and 10.5 mmol/L (1.22 and 25.5 mg/dL).