Validation of hemoglobin estimation using blood gas analyzer

Modern blood gas analyzers often have incorporated technology that allows hemoglobin measurement on the same blood sample used to measure pH, pCO₂ and pO₂. Clinicians working in a UK neonatal intensive care department where such an instrument was routinely used for blood gases were keen to exploit the newly available hemoglobin measuring technology as a point-of-care test (POCT).

They designed a study to compare performance of a blood gas analyzer with that of the reference hemoglobin method used in their local laboratory. Paired blood samples from 127 neonates were submitted for hemoglobin measurement by both methods. The range of results returned for laboratory testing was 3.0-22.6 g/dL, compared with 3.0-22.8 g/dL for the blood gas analyzer.

Mean and (SD) for laboratory results was 15.5 (3.2) g/dL, compared with 15.7 (3.6) g/dL for the blood gas analyzer. Mean difference between paired samples was 0.2 g/dL (0.7 %).

Further statistical analysis revealed that 50 % of hemoglobin results from the blood gas analyzer are within 0.5 g/dL of the reference laboratory method, 75 % are within 1.0 g/dL and 95 % are within 2.0 g/dL. The authors conclude that they have confirmed reliability of the POCT method, which only requires 95 µL of blood compared with 500 µL for laboratory hemoglobin estimation.