Performance Validation and Clinical Utility of a Smartphone-Based Colorimetric System for Differentiating Exudative and Transudative Pleural Effusions and Ascites via Total Protein Quantification

BACKGROUND: Total protein (TP) is a key indicator to differentiate between pleural effusion (PE) and ascites as exudate or transudate. Rapid quantification of TP can provide more accurate clinical treatment. OBJECTIVE: This study developed a smartphone-based colorimetric method for the rapid quantification of TP in PE and ascites by measuring the RGB values of reaction products and establishing a correlation between these values and TP concentration. METHODS: The smartphone colorimetric system was validated according to Clinical and Laboratory Standards Institute (CLSI) guidelines, assessing precision, accuracy, detection limit, linearity, and clinical reportable range. To evaluate clinical applicability, we compared results from 43 clinical samples (12 ascites and 31 PE specimens) obtained using the smartphone system with those from an automated biochemical analyzer. RESULTS: The G value showed the strongest correlation with TP concentration and was used to generate the standard curve. Validation studies confirmed that the smartphone system's precision and accuracy met clinical requirements, with analytical performance parameters including a limit of blank (3.36 g/L), limit of detection (9.08 g/L), and limit of quantification (13.09 g/L). The method demonstrated good linearity (15.8-93.7 g/L) and a wide clinical reportable range (13.09-374.8 g/L). Deming regression showed excellent agreement with no significant bias. The smartphone-based method and biochemical analyzer achieved near-perfect concordance in differentiating exudative and transudative fluids (PE κ=0.92, ascites κ=1.00). CONCLUSION: The smartphone-based colorimetric system provides a clinically viable solution for the rapid and quantitative measurement of TP in PE and ascites.