Estimation of Haemoglobin with Arterial Blood Gas Analyzer Compared to Conventional Laboratory Methods in Intensive Care Unit

Abstract

Background: Haemoglobin (Hb) estimation plays a pivotal role in clinical decision-making, particularly in Intensive Care Units (ICUs), where timely and accurate results are essential for managing critically ill patients. Traditional laboratory methods are considered the gold standard for haemoglobin measurement due to their high accuracy but they often involve delays caused by sample transport and processing. Arterial Blood Gas (ABG) analyzers, which are widely used at the bedside for evaluating oxygenation and acid–base balance, nowadays real-time haemoglobin estimation through co-oximetry technology. However, concerns regarding the accuracy and clinical reliability of these bedside haemoglobin readings persist. Aim: This study aimed to compare haemoglobin levels measured by ABG analyzers with those obtained from conventional laboratory hematology auto analyzers, to evaluate the accuracy, correlation, and agreement of ICU settings in Bangladesh. Methods: A cross-sectional study was conducted involving 50 adult patients admitted to the ICU of Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh. For each patient, simultaneous blood samples were collected and analyzed for haemoglobin concentration using both the ABG analyzer (Radiometer ABL800 FLEX) and the department of laboratory medicine in hematology auto analyzer (Sysmex XN-Series). Descriptive statistics, Pearson correlation, Paired t-tests, and Bland-Altman analyses were performed using SPSS version 26 to assess the level of agreement and clinical acceptability between the two methods. Results: The mean haemoglobin level obtained via ABG analysis was 13.12 ± 0.63 g/dL, while the laboratory method yielded a mean of 13.23 ± 0.66 g/dL. The difference between the two means (-0.11 g/dL) was statistically non-significant (p = 0.09). The Pearson correlation coefficient was r = 0.986, indicating a very strong positive correlation. In 84% of cases, the difference in haemoglobin values between the two methods was within ±0.5 g/dL, suggesting a high level of clinical agreement. No significant discrepancies were noted across demographic subgroups such as sex or age. Bland-Altman analysis confirmed strong agreement, with most differences lying within the 95% confidence limits. Conclusion: The findings suggest that ABG analyzers provide haemoglobin measurements closely aligned with those of conventional laboratory methods, supporting their use for rapid, point-of-care decision-making in ICU settings. Despite minor discrepancies in a small subset of patients, the overall agreement supports the clinical utility of ABG-derived haemoglobin values, particularly in time-sensitive scenarios. However, laboratory confirmation is recommended when precise haemoglobin estimation is critical, such as in transfusion decisions.