Urinary orosomucoid: validation of an automated immune turbidimetric test and its possible clinical use

Abstract

IntroductionBesides routine serum markers of inflammatory diseases, the diagnostic potential of selected urinary proteins has not been fully exploited yet. Former studies revealed that urinary orosomucoid (u-ORM) might have complementary information in inflammatory disorders. Our aim was to develop and validate a fully automated method for u-ORM measurements and to evaluate its potential clinical impact on systemic inflammatory diseases.Materials and methodsA particle-enhanced immune turbidimetric assay was validated for a Cobas 8000/c502 analyzer to determine u-ORM levels. Spot urine samples from 72 healthy individuals, 28 patients with Crohn’s disease and 30 septic patients were studied.ResultsOur assay time was 10 minutes and the detection limit of u-ORM was 0.02 mg/L. The intra- and inter-assay imprecision expressed as CV was less than 5%, and the recovery ranged between 95–103%. Within 10 to 60 years of age, a preliminary reference range for urinary orosomucoid/creatinine ratio (u-ORM/u-CREAT) was found to be 0.08 (0.01–0.24) mg/mmol [median (2.5–97.5 percentiles)]. Compared to controls, a five-fold increase of u-ORM/u-CREAT values in Crohn’s disease and approximately a 240-fold increase in sepsis were observed.ConclusionsWe set up a fast, sensitive and precise turbidimetric approach for automated u-ORM determination. Our highly sensitive assay is ideal for routine u-ORM measurements and might be a potential novel laboratory test in the management of systemic inflammatory processes.

Elevated urinary orosomucoid excretion as a novel biomarker in Crohn’s disease

“…Thereby, u‐ORM fulfils today's general medical demands: the measurement is simple, rapid, cheap and accurate . Moreover, high stability of u‐ORM was noted in our previous paper …”

“…ORM is normally excreted into the urine in low amounts, and recent studies suggested that urinary orosomucoid (u‐ORM) vs se‐ORM might provide more valuable information on the course of inflammatory disorders and is a non‐invasive tool. Elevated u‐ORM levels were reported in acute and chronic diseases related to inflammatory activation such as sepsis, diabetes, systemic lupus erythematosus, rheumatoid arthritis and even following cardiac surgery . Previously, we identified increased ORM levels in urine samples of CD patients as well …”

“…Orosomucoid can be produced by hepatocytes, leucocytes and endothelial cells in response to cytokine stimuli, and it exhibits anti‐inflammatory and immunomodulatory function during inflammatory processes . Serum concentration of ORM is well studied in CD; however, besides our recent initial experience, the benefit of u‐ORM as an inflammatory marker has not been investigated yet in association with CD …”

“…Hs‐CRP, ESR, WBC, platelet count (PLT), se‐ORM, urinary total protein (u‐TP), urinary albumin (u‐ALB) and urinary creatinine (u‐CREAT) were measured by routine procedures. U‐ORM was determined on Cobas 8000/c502 analyzer (Roche, Diagnostics GmbH, Mannheim, Germany) using our novel immune turbidimetric assay as was previously reported . U‐ORM and u‐ALB levels were expressed as u‐ORM/u‐CREAT and u‐ALB/u‐CREAT ratios to reduce the effect of different hydration states as recommended by others .…”

“…Elevated u-ORM levels were reported in acute and chronic diseases related to inflammatory activation such as sepsis, diabetes, systemic lupus erythematosus, rheumatoid arthritis and even following cardiac surgery. [12][13][14][15][16] Previously, we identified increased ORM levels in urine samples of CD patients as well. 15,17 In the present work, we studied u-ORM excretion in adult and paediatric CD patients to assess u-ORM as a possible objective activity marker of CD.…”