[Comparison of the Accuracy of the Measurement of Fetal Hemoglobin by Blood Gas Analysis and by Laboratory Gold Standard: a Prospective Diagnostic Study].

BACKGROUND

In neonatologic clinical practice and research the percentage of fetal hemoglobin (HbF) of total hemoglobin can be of interest. Blood gas analyzers offer the measurement of HbF. However, it is not known if results are accurate enough to apply in clinical decision-making or scientific questions. In this prospective diagnostic study, we examined the accuracy of HbF measurement by a blood gas analyzer.

METHODS

On a neonatal intensive care and neonatal ward, the percentage of HbF was measured using both the laboratory gold standard (HbFlab, reference method) and the blood gas analyzer (HbFgas) (ABL 800 Flex, Radiometer). Agreement of HbFlab and HbFgas was assessed by the Bland-Altman method including bias and limits of agreement and by calculation of the root mean square error (RMSE).

RESULTS

Thirty-five measurements in 23 term and preterm infants with a median body weight of 2190 g (min-max 967-3800 g) and a median postmenstrual age of 36+1 weeks (min-max 29+6-43+2) were performed. The Bland-Altman diagram for the measurement of HbF(gas) versus HbF(lab) shows an overestimation of HbF by the blood gas analyzer (bias 9.3%, limits of agreement 1 to 17.6%). RMSE was 10.2%; 45.7% of HbFgas measurements were >10% out of range from HbFlab. There was no influence of age, body temperature or oxygen saturation on the bias (p=0,132; p=0,194; p=0,970), but bias increased with increasing HbFlab (Pearson correlation r=0,426; p=0,011).

CONCLUSION

The measurement of HbF in term and preterm infants by a blood gas analyzer lacked sufficient agreement with that of the reference method to recommend this application for clinical decision-making or scientific purposes.