c-peptide and Hemolysis

The major aims of this study were to determine whether a single session of resistance exercise would alter insulin sensitivity, glucose effectiveness, and C-peptide response to glucose challenge in a group of previously sedentary, postmenopausal women.. Ten postmenopausal women (aged 57.5 +/- 1.6 yr) were studied. Each participant underwent two frequently sampled intravenous glucose tolerance tests (FSIVGTT): without prior exercise (no exercise), and postexercise (15 h after a session of resistance exercise: three sets of 10 repetitions performed at 50%, 75%, and 100% of 10-repetition maximum for 7 exercises). Insulin sensitivity and glucose effectiveness were determined according to Bergman's minimal model procedure. In addition, C-peptide concentration and glucose disappearance were measured.. There was no significant difference between trials for insulin sensitivity, glucose effectiveness, glucose disappearance, or area under the curve (AUC) for glucose or insulin during the glucose challenge. AUC for C-peptide tended (P = 0.059) to be 10% higher in the postexercise versus no exercise trial, and C-peptide values were significantly (P < or = 0.02) higher at several time points (60, 70, 140, and 180 min) during the postexercise compared with no exercise trial.. In contrast to previously reported results with young men and women after a single bout of endurance exercise, insulin sensitivity was unaltered by a single session of resistance exercise in postmenopausal women. Higher plasma C-peptide values concomitant with unchanged insulin values provide evidence that resistance exercise may have induced a slightly higher insulin secretion and a proportional increase in insulin clearance.

Topics: Area Under Curve; C-Peptide; Creatine Kinase; Diet; Exercise; Female; Glucose; Glucose Tolerance Test; Hemolysis; Humans; Insulin; Insulin Secretion; Middle Aged; Postmenopause; Weight Lifting

To examine the effect of phlebotomy-induced hemolysis on serum insulin and C-peptide measurement by an immunochemiluminometric assay.. As part of a study designed to evaluate β-cell function in a group of adults with newly diagnosed type 2 diabetes, we tested insulin and C-peptide levels in 1,048 samples. In order to evaluate the effect of phlebotomy-induced hemolysis, we determined insulin and C-peptide levels simultaneously in hemolyzed and nonhemolyzed samples.. Forty-seven (4.5%) of the 1,048 samples were affected by hemolysis. In 26 cases, we had paired hemolyzed and nonhemolyzed serum samples that allowed a simultaneous comparison. We found that all degrees of hemolysis led to a significant decrease in insulin level. In hemolyzed serum, the median (interquartile range) of the insulin was 5.6 (1.8 to 24.3) mIU/L, versus 21.3 (11.4 to 48.5) mIU/L in nonhemolyzed serum, representing a 25 to 98% loss. This phenomenon was not found for C-peptide levels.. Clinicians have to be aware that even a mild degree of phlebotomy-induced hemolysis has a significant effect on serum insulin level determination, which can lead to misinterpretation of test results. This finding has important implications, especially in the evaluation of suspected cases of hyperinsulinemic hypoglycemia.

Topics: Aged; Blood Chemical Analysis; C-Peptide; Diabetes Mellitus, Type 2; Female; Hemolysis; Humans; Immunochemistry; Insulin; Luminescent Measurements; Male; Middle Aged; Phlebotomy

We evaluated new immunochemiluminometric assays (ICMAs) for insulin and C-peptide (ADVIA Centaur Insulin & C-Peptide-Serum assays). Both ADVIA Centaur assays are two-site sandwich immunoassays using direct chemiluminescent technology. Precision was investigated using serum pools at three levels of the two analytes, measured in duplicate for 10 days. Total Coefficient of Variations (CVs) were 5, 7 and 4% for insulin and 9, 6 and 10% for C-peptide, with intra-assay precisions of 5, 4 and 5% and 5, 3 and 3%, respectively. The minimum detectable concentrations were 0.5 mU/L and < 0.1 microg/L for insulin and for C-peptide, respectively. Day-to-day reproducibility of single measurements was 5.4, 7.1 and 4.3% for pools with an insulin concentration of 0.6 mU/L, 2.0 mU/L and 4.0 mU/L; it was 4.4, 6.6 and 5.3% for pools with a C-peptide concentration of 0.2, 0.3 and 1.0 microg/L. The functional sensitivity did not differ from 3 SD Minimal Detectable Concentration (MDC) (0.5 mU/L for insulin and < 0.1 microg/L for C-peptide). The linearity was good in the range of 0.6-20 mU/L for insulin and 0.3-9 microg/L for C-peptide. The comparison with the RIA used in our laboratory was analyzed by Passing-Bablok and Bland-Altman plots and revealed a proportional bias of approximately 20% (slope: 1.20; CI: 1.14 to 1.26) for C-peptide and a systematic bias of -1.6 mU/L (slope: 0.94; CI: 2.7 to -0.5) for insulin which should not have any clinical consequence in the interpretation of results. Finally, we tested the influence of hemolysis on insulin in serum and plasma and found the same negative effect for both samples when more than 2% of red cells were hemolyzed, and this effect increased with the lag time before freezing. In conclusion, both assays were satisfactorily correlated with the routine RIA test used in our laboratory. The major problem was the sensitivity to hemolysis which is common to all insulin immunometric assays.

Topics: Autoanalysis; C-Peptide; Diabetes Mellitus; Hemolysis; Humans; Immunoassay; Insulin; Luminescent Measurements; Reproducibility of Results

Venous blood was taken at the end of a glucose infusion test in 19 individuals and divided into four aliquots, 3 of which were variably haemolysed by repeated passage through a 23-gauge needle to simulate traumatic venepuncture. Plasma insulin (measured by both a charcoal separation and a double-antibody method), C-peptide, and haemoglobin were measured in each aliquot, and haemolysis was also assessed visibly. A significant loss of immuno-assayable plasma insulin was found in samples with only a trace of visible haemolysis, with up to 90% lost in severely haemolysed samples. Plasma C-peptide was unaffected by haemolysis. This represents an additional advantage for the use of plasma C-peptide in assessing insulin secretion.

Topics: C-Peptide; Diabetes Mellitus, Type 2; Diagnostic Errors; Hemoglobins; Hemolysis; Humans; Insulin; Radioimmunoassay

Topics: C-Peptide; Circadian Rhythm; Complement System Proteins; Hemolysis; Humans; Immunoenzyme Techniques; Insulin; Quality Control