Creatinine Clearance

What this laboratory test evaluates

The Creatinine Clearance test is a convenient means of assessing renal function. Toxic metals and xenobiotics—including some pharmaceutical agents—are nephrotoxic and can decrease efficiency of glomerular filtration. Efficient glomerular filtration is critical during chelation therapy in which there is increased mobilization of toxic elements resulting in elevated demands on renal clearance. Assessment is highly recommended for determination of the appropriate dose of a chelating agent for an individual patient and for weighing the advisability of prescribing a variety of drugs.

Creatinine is neither secreted nor reabsorbed by renal tubules, thus urine creatinine can be used to measure renal function through assessment of glomerular filtration. Creatinine excretion is independent of urine flow, and the plasma concentration of creatinine is relatively constant. Therefore, the rate of creatinine clearance can be determined by analyses of creatinine in a timed urine collection and a single serum specimen collected during the same time period.

The quantity of creatinine formed in the body is related to muscle mass and does not change significantly with dietary variability. Heavy metals such as mercury, cadmium and lead are potent nephrotoxins which can markedly decrease renal function and result in increased levels of toxic substances in the body. Safe chelation therapy is highly dependent upon the adequacy of renal function. Excessive mobilization of toxic metals to poorly functioning kidneys can exacerbate kidney damage. Therefore, it is highly recommended that the rate of creatinine clearance be measured in order to determine the appropriate dosage of a chelating agent for each individual patient. Periodic reassessment of the clearance rate is also recommended and can serve to monitor therapeutic effectiveness.

Pharmaceutical agents such as some antihypertensive agents should be prescribed with caution, especially in patients with marginal kidney function. Determination of creatinine clearance is therefore appropriate before placing patients on certain therapeutic regimens. Assessment of renal function is also warranted for patients with known renal disease or for those at risk for renal dysfunction. For renal patients, the rate of creatinine clearance indicates whether dietary protein restriction is warranted. Reference ranges are provided for individuals of normal weight for height. The clearance rate corrected for body surface area in square meters can also be calculated.

It is essential that the blood specimen be drawn some time during the timed urine collection period. To facilitate compliance and accuracy of test results, detailed patient instructions are provided with the test kit.

Useful for:• Planning Detoxification Therapy
• Kidney Function

Additional test information

The Creatinine Clearance test is the most widely used test for estimating glomerular filtration rate (GFR) and renal function. GFR assessment is highly recommended for weighing the advisability of prescribing a variety of drugs, including chelating agents. The test requires a timed urine collection and a single serum specimen collected during the same time period.

Collection and processing

• Sample type: Urine, Serum
• Fasting: No
• Estimated laboratory processing: Results should arrive 2 to 4 days after the lab receives samples.

How Sunridge uses laboratory information

Sunridge considers the medical question, symptoms, history, medications, prior results, and whether the finding could change care before recommending testing. A laboratory result is not interpreted in isolation and does not establish a diagnosis by itself.

Before requesting this test

Availability, collection requirements, eligibility, and processing estimates can change. Sunridge reviews each request and, when appropriate, creates the order through Fullscript. Follow the current instructions supplied with the approved order.