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2. C-Peptide Elecsys Reagent Kit, Cat. No. 03184897 - 100 tests

The electrochemiluminescence immunoassay “ECLIA” is intended for use on the Roche Elecsys 1010/2010 and MODULAR ANALYTICS E170 (Elecsys module) immunoassay analyzers.

Principle:

Sample, a biotinylated monoclonal C-peptide-specific antibody, and a monoclonal C-peptide-specific antibody labeled with a ruthenium complex (Tris(2,2’-bipyridyl)ruthenium(II)-complex (Ru(bpy)2+3 ) react to form a sandwich complex. After addition of streptavidin-coated microparticles, the complex becomes bound to the solid phase via interaction of biotin and streptavidin. The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell.  Application of a voltage to the electrode then induces chemiluminescent emission which is measured by a photomultiplier. Results are determined via a calibration curve which is instrument-specifically generated by 2-point calibration and a master curve provided via the reagent barcode.

Specimen Collection and Preparation:

Only the specimens listed below were tested and found acceptable.
1.  Serum collected using standard sampling tubes or tubes containing separating gel.
2.  Li-heparin and K3-EDTA plasma.
Criterion: Recovery within 90-110% of serum value or slope 0.9-1.1+ coefficient of correlation > 0.95.
Assay within 2-3 hours, or store frozen at –20oC for 1-2 weeks.

Measuring Range:

3 - 13300 pmol/L or 0.01-40 ng/mL (defined by the lower detection limit and the maximum of the master curve).
Values below the detection limit are reported as < 3 pmol/L (< 0.01 ng/mL).
Values above the measuring range are reported as > 13300 pmol/L (> 40 ng/mL)

Reference Ranges:  

370 – 1470 pmol/L

Precision:

Serum and plasma:
 Reproducibility was determined using Elecsys reagents, pooled human sera, and controls in a modified protocol (EP5-A) of the NCCLS (National Committee for Clinical Laboratory Standards): 6 times daily for 10 days (n = 60); human serum 3 at one day 5 times (n = 59); within-run precision on MODULAR ANALYTICS E170 analyzer (n = 21). The following results were obtained:
 MODULAR ANALYTICS E170
E170                                        Within-run precision                                    Total precision

Sample Mean
pmol/L

SD
 pmol/L

CV
%

Mean
pmol/L

SD
pmol/L

CV
%

MC 3

330

2

0.6

310

6

1.9

Human serum 2

640

3

0.5

610

10

1.6

Human serum 3

2000

19

0.9

1920

44

2.3

Human serum 4

5990

54

0.9

 

 

 

Human serum 5

8590

126

1.5

 

 

 

PreciControl MA1

700

6

0.8

680

11

1.6

PreciControl MA2

3600

31

0.9

3390

55

1.6

Analytical Sensitivity (lower detection limit):

3 pmol/L (0.01 ng/mL)
The detection limit represents the lowest measurable analyte level that can be distinguished from zero. It is calculated as the value lying two standard deviations above that of the lowest standard (master calibrator, standard 1 + 2 SD, within-run precision, n = 21).

Method Comparison:

Serum
A comparison of the Elecsys C-Peptide assay (y) with a commercially available C-peptide assay (x) using clinical serum samples gave the following correlations:
Number of samples measured: 266
Passing/Bablok                    Linear regression
y = 1.07x + 0.03                   y = 1.11x - 0.15
τ = 0.962                              r = 0.996
SD (md68) = 0.117               Sy.x = 0.242
The sample concentrations were between approx. 157 and 7260 pmol/L or approx. 0.470 and 21.8 ng/mL.

Analytical Specificity:

For the monoclonal antibodies used, the following cross-reactivities were found:

Substance

Concentration tested
μg/mL            

Cross-reactivity
 %

Proinsulin, humane

0.10

32.5

Insulin, human

8.66

0.005

Insulin, porcine

7.50

not detected

Insulin, bovine

7.69

not detected

Somatomedin(IGF-I)

1.0

not detected

Human Growth Hormone

10.0

not detected

Glucagon

10.0

not detected

The Elecsys C-Peptide assay uses two monoclonal antibodies specifically directed against human C-peptide. The antibodies show cross-reactivity with the C-chain of human proinsulin and presumably with partially processed proinsulins (split products). The concentrations of proinsulin and split products of fasting healthy subjects are 100 times lower than the C-peptide concentrations and therefore the cross-reactivity is of no clinical significance. In patients with insulinoma, the proinsulin concentrations are reported as up to 60-fold higher than those from fasting healthy subjects.

 

For more information, please contact the Core Laboratory manager or director.