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Use of Cystatin C to Assess Kidney Function



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Laboratory Assessment of Kidney Function: What Can We Measure?

Slide 8

August 2011

The laboratory plays a key role in the diagnosis and staging of chronic kidney disease. In order to detect kidney damage independent of GFR, tests include a urinalysis and quantification of protein in the urine. Abnormalities that would indicate CKD include proteinuria, albuminuria, and formed elements such as red cell casts. Sometimes patients have more subtle abnormalities that might be detected on a blood electrolyte panel or more sophisticated testing. Examples include an inability to acidify the urine, called renal tubular acidosis, or an inability to concentrate the urine, called nephrogenic diabetes insipidus. Finally, radiology studies might detect evidence of kidney scarring, also diagnostic of CKD by
criterion 1.

As mentioned above, criterion 2 is entirely based on your GFR number. There are 2 methods to establish what a person’s GFR is. We can directly measure GFR. Strategies here would include 24-hour urine for creatinine clearance, or specialized testing such as an inulin clearance or iothalamate clearance techniques. Although these methods are useful in many settings, they are more involved and costly, and not particularly suitable for mass screening or frequent monitoring of patients. Fortunately, methods have been developed to estimate GFR based upon simple blood tests.

What Can We Measure?

 


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