Patients undergoing kidney assessment ask the difference between urine creatinine and serum creatinine. Although both tests are done in the laboratory, they differ in many aspects. It is important to know each of them so that you can prepare correctly during your laboratory visit.
What sample is used for the test of Urine Creatinine and Serum Creatinine?
The first difference between urine creatine and serum creatine is the sample used for the test. Obviously, urine creatinine requires you to collect urine sample. However, this is not the same as the routine urinalysis that you know. Since the test measures the amount of creatinine, you need to carefully collect your urine sample for 24 hours.
If you are not informed about this difference between urine creatinine and serum creatinine, you might not be able to bring your sample correctly.
Urine 24-hour collection means placing all your pee in a single container for the next 24 hours, including the whole day and night. The laboratory usually provides you with the appropriate vessel with preservatives in it to keep your urine stable during the whole collection.
If it is not provided, you can use a clean bottle and keep the urine in a cooler to prevent bacterial decomposition.
To ensure that you get the correct difference between urine creatinine and serum creatinine, record the time you started your collection, collect all urine and end on the same time the following day. Be sure not to spill any urine and do not miss out any portion of it.
For serum creatinine, blood is the sample required.
Your medical technologist collects blood from you so there is no much hassle involved on your part. On the day of your examination, just go to the laboratory and have yourself prepared for the blood extraction. There is no need to fast since there is no difference between urine creatinine and serum creatinine in terms of patient preparation. Just expect a slight but tolerable pain during the needle insertion.
If you have allergies to latex, fear of needle, fainting tendencies or any other concerns, verbalize them to your health care provider.
Why is serum creatinine and urine creatinine requested?
The indication for the request is another important difference between urine creatinine and serum creatinine. Serum creatinine measures the amount of the substance in the blood. Levels coincide with kidney damage.
This is the reason why doctors request for the test for assessment of kidney functions.
However, it is not requested on its own because it is not highly sensitive in diagnosing early stages of kidney problems. Most physicians also request other kidney function tests like Blood Urea Nitrogen.
Urine creatinine is requested to get what is called as the Glomerular Filtration Rate (GFR).
It represents how well the kidneys are able to clear substances in the body. In easier terms, it tells you the filtration ability of your organs. Remember your anatomy class in school? Your teacher told you that kidneys filter the blood and remove toxic substances through the urine.
Those substances include creatinine.
By measuring urine creatinine, your doctor can have a rough assessment on how good are your organs in cleaning your blood. However, a single test does not lead to a definite diagnosis. Your health care provider confirms it by requesting additional tests.
What is the NORMAL VALUE for urine creatinine and serum creatinine?
Because there is a difference between urine creatinine and serum creatinine, their normal values also differ. Each laboratory can set their reference range but the slight differences usually do not matter. Generally, the values are set based on gender. Women have lower levels compared with men because they have a lower muscle mass. Serum creatinine is 0.6 to 1.1 mg/dL in women and 0.7-1.3 mg/dL in men.
What is creatinine?
Now that you know the difference between urine creatinine and serum creatinine, your next goal is to know what creatinine is all about.
Creatine is a byproduct of muscle metabolism and it is constantly being removed from the body through the urine.
Everyone has creatinine in their blood but abnormal rise is see in kidney problems. But apart from this, the difference between urine creatinine and serum creatinine occurs during muscle injury, diet rich in protein and meat, and use of some drugs.
Thus, it is important that you inform your health care provider if you are taking any drugs or you are on a special diet.
During the interpretation on the difference between urine creatinine and serum creatinine, your doctor also considers your age and body size. These variables also affect the normal values and thus, may affect the interpretation.
Overall, apart from the sample used and normal values, the difference between urine creatinine and serum creatinine is not critical. For as long as you follow your doctor’s order during the test, you are sure that you will get the most accurate results.
