Definition
A quantitative analysis of serum creatinine levels, the serum creatinine test provides a more sensitive measure of renal damage than do blood urea nitrogen levels because renal impairment is virtually the only cause of creatinine elevation.
Creatinine is a non-protein end product of creatinine metabolism that appears in serum in amount proportional to the body’s muscle mass.
Purpose
- To assess glomerular filtration.
- To screen for renal damage.
Procedure
Patient Preparation
- Confirm the patient’s identity using two patient identifiers according to facility policy.
- Explain to the patient that the serum creatinine test is used to evaluate kidney function.
- Tell the patient that the test requires a blood sample.
- Explain to the patient that he may experience slight discomfort from the tourniquet and the needle puncture.
- Instruct the patient that he doesn’t need to restrict food and fluids.
- Notify the laboratory and the practitioner of medications the patient is taking that may affect test results; they may need to be restricted.
Implementation
- Perform a venipuncture and collect the sample in a 3 or 4 ml clot activator tube.
- Handle the sample gently to prevent hemolysis.
- Send the sample to the laboratory immediately.
Nursing Interventions
- Send the sample to the laboratory immediately.
- Apply direct pressure to the venipuncture site until bleeding stops.
- Assess the venipuncture site for hematoma formation; if one develops, apply pressure.
- Inform the patient that he may resume his usual medications that were discontinued before the test, as ordered.
Interpretation
Normal Results
- In men, 0.8 to 1.2 mg/dl (SI, 62 to 115 pmol/L)
- In women, 0.6 to 0.9 mg/dl (SI, 53 to 97 pmil/L)
Abnormal Results
- Elevated levels generally indicate renal disease that has seriously damaged 50% or more of the nephrons.
- Elevated levels may also indicate gigantism and acromegaly.
Interfering Factors
- Ascorbic acid, barbiturates, and diuretics that may possibly increase.
- Exceptionally large muscle mass, such as found in athletes that may possibly increase despite normal renal function.
- Phenolsulfonphthalein given within the previous 24 hours (possible increase, if the test is based on Jaffe’s reaction.
Complications
- Hematoma to the puncture site.
