Creatinine (PAP)

Serum creatinine concentration is routinely used as a surrogate to evaluate renal function by incorporating the serum creatinine levels into equations that estimate glomerular filtration rate. GFR calculations are often used to identify and classify patients with kidney failure. Bias in serum creatinine measurements has been a source of concern because of the potential to misclassify patients with respect to renal function. When a renal disorder is suspected, the ratio of BUN to serum creatinine may be useful in diagnosing the location of the problem. A normal ratio is 10–20 mg/dL BUN to 1 mg/dL creatinine. A high (more than 20:1) BUN to creatinine ratio suggests pre-renal disease, whereas a low (less than 10:1) ratio is indicative of renal disease.

Currently, there are two formats are available for measuring Creatinine: (1) Jaffe assays (alkaline picrate) and (2) enzymatic assays. However, the former being cheap and widely preferred method is more vulnerable to interference in comparison to the latter which eventually leads to suggestions by professionals that the Jaffe assay should be abandoned in favour of the enzymatic assay.