Hemolysis is a major cause of variability in insulin measurement during oral glucose tolerance test in children.

BACKGROUND

The oral glucose tolerance test (OGTT) is widely employed to evaluate insulin resistance in children with growth hormone deficiency. Due to the difficulty in blood sampling, hemolysis is a frequent pre-analytic interference. The present study was performed to characterize the effects of hemolysis on insulin assays, in order to assess the need to generate automatic hemolysis reports and/or to reject hemolyzed samples.

METHODS

Insulin plasma levels were measured using a Siemens ADVIA Centaur on samples obtained from children with suspected GH deficiency at risk for insulin resistance during OGTT.

RESULTS

The presence of hemolysis (with a concentration of free hemoglobin above 75 mg/dL) promotes a dose- and time-dependent decrease in immunoreactive insulin at any time-point evaluated during OGTT. As a consequence, the variability of insulin is particularly high (often exceeding 100% of the mean value) as compared to that of glucose. This variability is markedly reduced after removal of the hemolyzed samples.

CONCLUSIONS

When hemolysis is not taken into account a misinterpretation of insulin secretion pattern can occur. It is therefore imperative to: (i) analyze blood samples immediately after sampling, (ii) reject samples with a concentration of free hemoglobin equal to or above 125 mg/dL and (iii) always report the possible interference.