B-415 Agreement Between Colorimetric Roche Cobas PRO and ICP-MS Zinc Assays in Blood Samples
Abstract
Accurate measurement of zinc concentrations in blood is essential for assessing nutritional status and diagnosing deficiency. This study compared zinc results obtained using the Roche Cobas Pro colorimetric assay with those generated by inductively coupled plasma mass spectrometry (ICP-MS), the analytical reference method. A total of 22 patient serum blood samples collected in royal-blue top tubes, spanning a concentration range of 55–97?µg/dL, were analyzed by both techniques. This study was conducted on January 2026 between the laboratory of King Abdelaziz Medical City and Medical Diagnostic laboratory of Dr Suliman Al-Habib Sahafah Hospital, both in Riyadh of Saudi Arabia. Direct colorimetric test without deproteinization of the sample. At pH 8.6, in a buffered media, zinc reacts with the specific compound (5-Br-PAPS): Bromo-pyridylazo propyl-N-(3-sulfopropyl) amino] phenol, forms a stable-colored complex and measured at wavelength 560nm. The color intensity is proportional to the amount of zinc present in the sample. The results of CAP proficiency samples were also compared for the two assays. Method comparison demonstrated strong agreement, with a correlation coefficient of ??= 0.9269, indicating a high degree of linear association across the tested range. There were 6 samples (27%) with zinc deficiency by colorimetric method with 83% agreement with ICP-MS method. On the other hand, a 100% agreement was found in the normal samples between the two assays. The reference interval was verified for the colorimetric Roche Cobas and found to be between 68 to 107 ug/dL. The CAP proficiency of 3 samples (R-01, R-02, R-03) for years 2024 and 2025 have shown a good agreement between the two assays. While minor proportional differences were observed, the overall performance of the Cobas colorimetric method showed good concordance with ICP-MS, supporting its suitability for routine clinical zinc measurement when rapid, high-throughput analysis is required.