Accuracy of point-of-care HbA1c testing in pregnant women

In New Zealand, it is recommended that all pregnant women have a haemoglobin A1c (HbA1c) test performed with their booking antenatal bloods to identify previously unrecognised diabetes. However, screening rates in some groups are low. Use of a point-of-care device may improve compliance with screening.

To assess the accuracy of the COBAS b101 point-of-care system referenced against a laboratory method, for measurement of HbA1c levels in pregnant women.

Convenience sample of 40 obese pregnant women enrolled in a clinical trial. HbA1c was assayed in paired capillary and venous whole blood samples using the COBAS b101 point-of-care system and Primus Ultra2 high performance liquid chromatography laboratory analyser, respectively. The accuracy of the point-of-care system was assessed by Bland-Altman analysis.

The mean (SD) laboratory HbA1c was 35.9 (2.0) mmol/mol. The COBAS b101 point-of-care system, compared with the laboratory reference method, had a small negative bias for HbA1c (-1.0 mmol/mol, 95% CI -2.0 to -0.03, P = 0.03) and relatively wide 95% limits of agreement (-7.2 to 5.1 mmol/mol).

In conclusion, we found that in pregnancy, the COBAS b101 point-of-care system has a small negative bias and modest point accuracy for HbA1c. When used to screen for previously unrecognised diabetes in pregnancy, appropriate COBAS b101 HbA1c point-of-care HbA1c thresholds for a negative and positive result are 7 mmol/mol below and 5 mmol/mol above the clinical threshold, respectively. Values between these limits should be confirmed by laboratory testing.