B-025 Validation of an open-channel assay for measuring serum angiotensin-converting enzyme (ACE) using the Cobas® Pro analyzer

Background Angiotensin-converting enzyme (ACE) is a zinc-dependent carboxypeptidase that plays a central role in the renin-angiotensin-aldosterone system. It is primarily expressed in pulmonary capillaries and renal epithelial cells, with two catalytic domains (C-terminal and N-terminal) involved in blood pressure regulation. Serum ACE measurement is crucial for diagnosing and monitoring ACE-related conditions, including sarcoidosis and other granulomatous diseases. This study aimed to validate an open-channel assay for serum ACE on the cobas® c 503 analyzer in accordance with Clinical Laboratory Standards Institute (CLSI) recommendations. Methods The analytical performance of an ACE open-channel assay (BÜHLMANN Laboratories AG) on the cobas® c 503 analyzer was evaluated. Assay parameters were established based on Roche recommendations for adapting cobas® c 502 – where ACE was previously being tested on – open channel parameters to the c503 analyzer.Validation included precision, correlation, linearity, and interference from hemolysis, icterus, and lipemia (HIL), using a total allowable error of 10%. The data were visualized using Microsoft Excel and analyzed following CLSI recommendations. Results Total imprecision of the assay was <6% across both manufacturer-provided quality control materials. Correlation with patient samples (n = 40) against the c502 ACE assay was excellent (R² = 0.974) over a concentration range of 10 – 157 U/L. The assay demonstrated excellent linearity across the analytical measurement range (4 – 140 U/L). Finally, the ACE assay exhibited tolerance to hemolysis, icterus, and lipemia up to Roche cobas serum indices thresholds of 50, 5, and 100, respectively. Conclusion Using a conversion system to transfer assay parameters from the cobas® c502 to the c503 analyzer, we established an ACE assay that exhibited excellent analytical performance in terms of precision, method comparison, linearity, and tolerance to HIL interferences.