Ordering information

(L) Indicates liquid option
(S) Indicates standard included in kit

Instrument Specific Applications (ISA's) are available for a wide range of biochemistry analysers. Contact us to enquire about your specific analyser.

Methodology

The Laboratory Working Group of the National Kidney Disease Education Program (NKDEP) released guidelines for the improvement of glomerular filtration rate (GFR) estimation as well as the measurement of serum creatinine (SCr). The recommendation included the recalibration and standardisation of SCr methods to be traceable to the isotope dilution-mass spectrometry (IDMS) reference method. Two IDMS traceable creatinine methods are commercially available: enzymatic assays and compensated Jaffe assays ¹.

Of the two enzymatic assays available, the Randox enzymatic creatinine assay converts creatinine to ammonia (NH3) and I-Methylhydantoin. Ammonia then reacts with α-oxoglutarate in the presence of GLDH with oxidation of the co-enzyme NADPH. The decrease of NADPH is proportional to the creatinine concentration and is measured at 340nm ^{1, 2}.

The Randox enzymatic creatinine assay exhibits high sensitivity and reproducibility with the added advantage of liquid ready-to-use reagents with good stability. The enzymatic method represents an improvement for use in the accurate and reliable determination of creatinine.

Physiological Significance

Homocysteine is a sulfur-containing amino acid produced by the intracellular demethylation of the essential amino acid, methionine. Homocysteine has three metabolic functions within the human body: firstly, to be remethylated into methionine; secondly, to enter the biosynthetic pathway of cysteine; and thirdly, to be released into the extracellular medium (blood and urine). The third metabolic function is the direct cause of elevated homocysteine concentrations in urine and plasma ^{1, 2}.

Renal Function

According to the National Institutes of health, the overall prevalence of chronic kidney disease (CKD) is approximately 14% ³. Creatinine is the most commonly utilised assay in the assessment of renal function ⁴. The National Kidney Disease Education Program recommends calculating GFR from SCr. Creatinine measurements are useful in the monitoring of disease progression, with the diagnosis of renal failure when SCr levels are greater than the upper normal interval ⁵.

Diabetes

Creatinine measurements are useful in the diagnosis and monitoring of diabetic nephropathy, the leading cause of kidney disease in patients commencing renal replacement therapy, affecting 40% of diabetics (type 1 and type 2) ⁶. The RENAAL risk score for end-stage renal disease (ESRD) emphasizes the importance of the identification of elevated SCr, alongside other renal markers, in the prediction of end-stage renal disease (ESRD) development in patients with type 2 diabetes mellitus (T2DM) and nephropathy ⁷.

COVID-19

Acute kidney injury (AKI) is a common complication in COVID-19 patients ⁸. The analysis of creatinine in COVID-19 patients on hospital admission and after 2 to 4 days highlighted impaired renal function and is the leading cause of death in these patients 9. The National Institute of Care Excellence (NICE), have set out four guidelines for acute kidney injury in hospitalised suspected or confirmed COVID-19 patients and highlights the importance of creatinine testing ¹⁰.

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