Objective New biomarkers for acute kidney injury are needed and urinary Cystatin C is one alternative. The objective was to validate a urinary Cystatin C method on Mindray BS-380 comparing urine samples from the Uppsala Longitudinal Study of Adult Men (ULSAM-77) and urine samples from a reference group for Cystatin C. A visual control for a relationship between Cystatin C and C-reactive protein (CRP) and interleukin 6 (IL-6) respectively was made. Methods Precision, linearity, recovery, interference, and stability of the urine cystatin C method were investigated. Comparisons were made between ULSAM-77 samples and a reference group samples consisting of ordinary people. Results The highest total imprecision was 10.24 % for the sample with the lowest concentration. The second lowest concentration had 4.21 % total variation coefficient. The linearity equation was y = 0.99x – 0.01 with an R2-value of 0.99. The recovery for all concentrations was always 91 % or more. No interference from hemoglobin at a concentration of 10 g/L was found. The samples were stable at +5°C for seven days. The median for the samples from ULSAM-77 was 0.09 mg/L and the median for the reference samples was 0.06 mg/L. There was no obvious relationship between Cystatin C and CRP/IL-6 from ULSAM-77. Conclusion   Reliable data of urinary Cystatin C can be analyzed on a Mindray BS-380. The level of urinary Cystatin C was higher for people age 77 than for those with a median age of 49. There was no correlation between the concentration of Cystatin C in urine and the levels of CRP and IL-6.

Cystatin C, a 13 kDa low molecular weight protein is an inhibitor of cysteine proteases. Due to its low molecular weight and positive charge at physiological pH, it is freely filtered by the glomerulus and catabolized after reabsorption by proximal tubular cells with a low concentration (0.03-0.3 mg/L) in urine amongst healthy subjects. Urinary cystatin C is a potential biomarker detection of acute kidney injury (AKI) in the acute phase when patients are submitted to the intensive care unit. The aim in this report was to perform a full method validation of urinary analysis of cystatin C on a high throughput chemical analyzer by particle-enhanced turbidimetric immunoassay (PETIA) at the University Hospital in Uppsala, Sweden. The antigen excess, linearity, lower limit of quantification (LoQ), recovery, assay precision, stability and interference caused by haemoglobin was evaluated. No hook effect was observed, the assay was linear over the studied interval <0.001-0.950 mg/L with a regression of R2=0.9994. The LoQ was calculated to 0.020 mg/L with a coefficient of variation (CV) ≤10% which was considered acceptable. The assay had a recovery between 93-100% and the assay precision had a total CV <3.5%. Cystatin C is stable for 3 days in room temperature and 14 days in +4C. The assay did not show any major interference with haemoglobin. The urinary cystatin C showed good precision and performance characteristics by measurements using PETIA all of which is a necessary qualification for a biomarker at a 24-h running routine laboratory.

Diabetes is a significant health burden worldwide. The most common types of diabetes, type 1 and type 2 diabetes are typically characterized by complete insulin deficiency and varying degrees of insulin deficiency, respectively. Glycated hemoglobin (HbA1c), formed when hemoglobin and glucose combine through glycation, can be used to monitor treatment in diabetic patients, and thus prevent future complications of the disease. HbA1c can be measured using point-of-care (POC) instruments, providing rapid results and immediate feedback on HbA1c levels. Measurement with POC instruments can reduce the need for additional visits for blood sampling, thereby lowering costs for both patients and healthcare systems. The main purpose of this study was to verify HbA1c on the POC instruments QuikRead Go and DCA Vantage by comparing the results with the reference method Cobas Pro and by comparing capillary and venous blood samples. The study utilized 30 venous patient samples, including 20 samples already analyzed on Cobas Pro and 10 samples collected venously and capillary from volunteer individuals. The coefficient of variation (CV) for QuikRead Go fell within the quality goal, while DCA Vantage exceeded the goal. The results demonstrated good agreement between capillary blood samples analyzed on POC instruments and venous samples analyzed on Cobas Pro. However, a statistically significant difference was found comparing venous samples analyzed on POC instruments and Cobas Pro. The results suggest that capillary sampling should be used for analysis on POC instruments. Certain limitations of the study should be considered when using QuikRead Go and DCA Vantage in practice.