Laboratory Test DirectoryShare
Measurements of creatinine are used in the diagnosis and treatment of renal disease. Serum creatinine measurements prove useful in evaluation of kidney glomerular function and in monitoring renal dialysis. However, the serum level is not sensitive to early renal damage and responds more slowly than blood urea nitrogen (BUN) to hemodialysis during treatment of renal failure. Both serum creatinine and BUN are used to differentiate prerenal and postrenal (obstructive) azotemia. An increase in serum BUN without concomitant increase of serum creatinine is key to identifying prerenal azotemia. With postrenal azotemia, both serum BUN and creatinine rise, but the rise is disproportionately greater for BUN.
Creatinine procedure is a kinetic modification of the Jaffe procedure in which creatinine reacts with picric acid at alkaline pH to form a yellow-orange complex. However, this reaction is not completely specific for creatinine since other reducing substances such as glucose, pyruvate, ascorbic acid, and acetoacetates will react with picrate to form a similar color. Fabiny and Ertingshausen found that alkaline creatinine picrate reaches maximum color development at a different rate than pseudo-creatinine material. Cook utilized different reaction rates of alkaline picrate positive substances to obtain greater specificity with the Jaffe reaction. The rate of change in absorbance at 520/800nm is proportional to the creatinine concentration in the sample.
Collect: Serum Separator Tube (SST)- 0.5 ml
Specimen preparation: Serum free from hemolysis is the recommended specimens. Allow blood samples to clot (15 mins). Separate the serum from the cells by centrifuging for 10 minutes. Store serum at 2-8°C until analysis.
Stability: Serum specimens are stable for 7 days refrigerated at 2 - 8°C and indefinitely when frozen (<-20°C).
At Accu Reference: Refrigerated -7 days: Frozen- 1 monthNOTE: * This test is approved for all states. *
Accu Reference Medical Laboratory
Male: 0.7 - 1.3 mg/dL
Female: 0.5 - 1.2 mg/dL
The assay Reportable Range is from 0.2 to 25.0 mg/dL. Samples exceeding the upper limit of linearity are diluted and repeated.