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BACKGROUND: Diagnosing acute kidney injury (AKI) and chronic kidney disease (CKD) relies on creatinine, which lacks optimal diagnostic sensitivity. The kidney-specific proximal tubular enzyme myo-inositol oxygenase (MIOX) catalyzes the conversion of myo-inositol (MI) to D-glucuronic acid. We hypothesized that proximal tubular damage, which occurs in AKI and CKD, will decrease MIOX activity, causing MI accumulation. To explore this, we developed an LC-MS/MS assay to quantify plasma MI and assessed its potential in identifying AKI and CKD patients. METHODS: MI was quantified in plasma from 3 patient cohorts [normal kidney function (n = 105), CKD (n = 94), and AKI (n = 54)]. The correlations between MI and creatinine were determined using Deming regression and Pearson correlation and the impact of age, sex, and ethnicity on MI concentrations was assessed. Receiver operating characteristic curve analysis was employed to evaluate MI diagnostic performance. RESULTS: In volunteers with normal kidney function, the central 95th percentile range of plasma MI concentrations was 16.6 to 44.2 µM. Age, ethnicity, and sex showed minimal influence on MI. Patients with AKI and CKD exhibited higher median MI concentrations [71.1 (25th percentile: 38.2, 75th percentile: 115.4) and 102.4 (77, 139.5) µM], respectively. MI exhibited excellent sensitivity (98.9%) and specificity (100%) for diagnosing CKD. In patients with AKI, MI increased 32.9 (SD 16.8) h before creatinine. CONCLUSIONS: This study unveils MI as a potential renal biomarker, notably elevated in plasma during AKI and CKD. Plasma MI rises 33 h prior to serum creatinine, enabling early AKI detection. Further validation and exploration of MI quantitation in kidney disease diagnosis is warranted.
RESUMO
OBJECTIVES: This article describes Pathologists Overseas (PO) experience supporting external quality assessment (EQA) programs in 10 clinical laboratories across 3 countries between 2009 and 2017. METHODS: Laboratories were enrolled in the condensed chemical pathology EQA program provided by the Royal College of Pathologists of Australasia Quality Assurance Program. Participants were given an initial 2- to 4-day in-person training, followed by 1 year of active feedback on performance via emails or phone calls by a PO volunteer. RESULTS: There were 2 performance metrics: percentage of reported results as a measure of compliance and percentage of acceptable reported results as a measure of accuracy. Laboratories demonstrated high compliance with result reporting, with medians of 69.9%, 71.7%, and 81.3% before, during, and after feedback, respectively. Concomitant medians for the percentage of acceptable reported results were 41.2%, 57.3%, and 53.5%, respectively. Six laboratories had low performance in terms of accuracy at baseline (<60%). Active feedback improved the percentage of acceptable reported results for these lower-performing laboratories. CONCLUSIONS: External quality assessment programs can be successfully adopted long term by laboratories in low-resource settings. Active feedback requires significant time and effort but could be especially beneficial for laboratories with poor baseline performance.