Challenges in Serum Albumin Measurements: A Comparative Study of the Bromocresol Green and the Capillary Zone...

Serum albumin (SA) is a key biomarker routinely used in clinical practice. Multiple analytical methods exist for its measurement, including bromocresol green (BCG) colorimetry and capillary zone electrophoresis (CZE). However, discrepancies between methods raise concerns regarding result consistency and clinical interpretation. This study aimed to compare the analytical concordance between BCG and CZE methods for SA measurement, and to assess their clinical interchangeability. A cross-sectional study conducted on 109 serum samples collected from patients undergoing serum protein electrophoresis at Bechir Hamza Children's Hospital. SA was measured using BCG and CZE. Descriptive statistics were calculated for each method. Paired t-test and Wilcoxon signed-rank test were used to assess differences in means. Method agreement was evaluated using Passing-Bablok regression, Intraclass Correlation Coefficient (ICC), Bland-Altman plot, and a confusion matrix. BCG significantly overestimated SA compared to CZE (41.49 ± 7.30 g/L vs. 37.48 ± 6.85 g/L; p < 0.001). Passing-Bablok regression revealed a regression line of y = 1.02x + 3.21, indicating a consistent positive bias. The R² value was 0.891, suggesting strong correlation. The ICC was 0.81 (95% CI 0.081-0.932), reflecting good agreement. The Bland-Altman analysis confirmed a mean difference of 4.01 g/L. Confusion matrix analysis showed perfect concordance in low albumin values but significant misclassification at higher levels, with BCG shifting many values into higher categories. While BCG and CZE methods show strong correlation, BCG consistently overestimates albumin concentrations. These findings underscore the need for method standardization and careful interpretation of results in clinical settings.