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Evaluation of the Haemoglobin Colour Scale and comparison with the HemoCue haemoglobin assay
1Department of Anaesthesia, Royal Cornwall Hospital, England. jpaddle@doctors.org.uk
Objective:
To evaluate the Haemoglobin Colour Scale developed by WHO for estimating haemoglobin concentration and to compare the results obtained using it and the HemoCue assay with those determined using a reference method, the Technicon H3 analyser.
Methods:
The Colour Scale and HemoCue assay were used to test 408 blood samples. Subsequently, Bland-Altman plots were determined and the proximity of the test results to those obtained using the reference method was determined.
Findings:
The mean difference between the Haemoglobin Colour Scale and the reference method was 0.19 g/dl (95% confidence interval: 3.50 g/dl below to 3.11 g/dl above); the corresponding value for the HemoCue assay was 0.50 g/dl (1.16 g/dl below to 0.16 g/dl above). Only 46.08% of the results obtained by means of the Colour Scale were within 1.0 g/dl of the reference method, whereas 95.34% of the HemoCue results fell within this limit; 22.79% of the Colour Scale results but none of the HemoCue results lay more than 2.0 g/dl from the reference method.
Conclusion:
The Haemoglobin Colour Scale test is too inaccurate for general use, particularly if devices such as the HemoCue are available.