Non-invasive haemoglobin estimation in patients with thalassaemia major

Objectives: This study aimed to validate pulse CO-oximetry-based haemoglobin (Hb) estimation in children and adults with thalassaemia major (TM) and to determine the impact of different baseline variables on the accuracy of the estimation. Methods: This observational study was conducted over a fve-week period from March to April 2012. A total of 108 patients with TM attending the daycare thalassaemia centre of a tertiary care hospital in Muscat, Oman, were enrolled. Spot (Sp) Hb measurements were estimated using a Pronto-7^® pulse CO-oximetry device (Masimo Corp., Irvine, California, USA). These were compared to venous samples of Hb using the CELL-DYN Sapphire Hematology Analyzer (Abbott Diagnostics, Abbott Park, Illinois, USA) to determine the reference (Ref) Hb levels. A multivariable linear regression model was used to assess the impact of baseline variables such as age, gender, weight, height, Ref Hb and blood pressure on the Hb estimations. Results: Of the 108 enrolled patients, there were 54 males and 54 females with a mean age of 21.6 years (standard deviation [SD] = 7.3 years; range: 2.5–38 years). Te mean Ref Hb and Sp Hb were 9.4 g/dL (SD = 0.9 g/dL; range: 7.5–12.3 g/dL) and 11.1 g/dL (SD = 1.2 g/dL; range: 7.5–14.7 g/dL), respectively. Te coefficient of determination (R²) was 21% with a mean difference of 1.7 g/dL (SD = 1.1 g/dL; range: -0.9–4.3 g/dL). In the multivariable model, the Ref Hb level (P = 0.001) was the only statistically significant predictor. Conclusion: Te Pronto-7^® pulse CO-oximetry device was found to overestimate Hb levels in patients with TM and therefore cannot be recommended. Further larger studies are needed to confirm these results.