Reproducibility of assays for steroid hormones, prolactin and insulin-like growth factor-1 in umbilical cord blood

HbA1c-testing: Evaluation of two point-of-care analysers

BACKGROUND

HbA_1c is a critical parameter for the medical management of patients with diabetes mellitus. Interventions that reduce HbA_1c levels lead to a diminution of microvascular complications. For two decades, point of care testing (POCT) methods have been regularly used to measure HbA_1c. The results significantly impact on the management of patients with diabetes mellitus and the accuracy of the results is critical. It is important to know the performance of common methods of HbA_1c measurements in daily life. We, therefore, aimed at evaluating the accuracy of two different analysers especially developed for POCT and compared them to a reference method.

METHODS

We prospectively tested two widely used POCT methods to measure HbA_1c, namely Afinion™ AS100 Analyzer (Axis-Shield, Oslo Norway) and DCA Vantage™ Analyzer (Siemens Healthcare Diagnostics, Tarrytown NY, US) in venous samples of 100 patients. As a reference method, we used the high-performance liquid chromatography method G8 HPLC used in the Biochemistry Laboratory of the Inselspital Bern. The National Glycohaemoglobin Standardization Program (NGSP) has certificated all methods used in this study. The comparability and degree of agreement was assessed using Bland-Altman plot.

RESULTS

The HbA_1c levels ranged from 33 to 116 mmol/mol (5.2-12.8%), 31-122 mmol/mol (5.0-13.3%) and 30-119 mmol/mol (4.9-13%) for Afinion™, DCA Vantage™ and G8 HPLC Analyzer, respectively. The 95% limits of agreement were between -0.84 and +0.30 for the Afinion™ and -0.71 and +0.29 for DCA Vantage™. The results of both POCT were significantly lower with a bias of -0.27% and -0.21% (p < 0.0001) for Afinion™ and DCA Vantage™ Analyzer, respectively.

CONCLUSIONS

The POCT methods tested in this study showed a good correlation with the laboratory reference method, however, with an overall negative bias.

Meta-analysis of sex difference in testosterone levels in umbilical cord blood

This meta-analysis reviewed published literature comparing human male and female umbilical cord total testosterone (T) levels. A total of 18 studies using 1,229 samples from 602 male and 627 female newborns were analysed using the RevMan 5 statistical package. Analysis using the inverse variance method based on a random-effects model revealed significantly higher cord T in boys than girls at a moderate effect size (Hedges' g = 0.57). There was significant heterogeneity between the 18 studies, although the five studies using direct assays showed no heterogeneity. For studies using extraction and chromatography, those that combined T from arterial and venous cord blood found a larger sex difference than those using only cord venous samples (Hedges' g = 0.94 vs 0.32); this suggests umbilical cord venous T is of maternal/placental origin and arterial T is of fetal origin. The wide range of T values between studies suggests high cross-reactivity in the assay methods reviewed.