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Which Blood Test Is Commonly Used To Evaluate Kidney Function

Tests For Kidney Disease

Medical Tests required to evaluate Kidney Functions | Dr. Rammohan

Kidney tests are important because kidney disease often has no symptoms until your kidneys are badly damaged. So, the only way to know how well your kidneys are working is to get tested. This is especially important for people who have diabetes, high blood pressure, or a family history of kidney disease.

Ask your doctor about these tests to check your kidneys. Kidney damage usually cannot be fixed. But if you find and treat kidney disease early, you may be able to keep it from getting worse.

When Should I Get A Renal Panel Test

A renal panel test can be used in a range of circumstances, and the doctor may include specific measurements depending on your situation.

As a diagnostic test, a renal panel is most frequently used when you have symptoms that could be explained by a kidney problem. Examples of symptoms that can be tied to kidney impairment or disease include:

  • Urinary changes including changes to the frequency, quantity, or appearance of your urine
  • Unexplained swelling, especially in your arms, hands, legs, and/or face
  • Itching
  • Fatigue
  • Muscle cramps or pain

A test like the renal panel may also be used for diagnosis when you have general symptoms without a clear cause or are being evaluated in an urgent care or emergency setting.

As a screening test, the renal panel or other tests of kidney health are most often prescribed if you have certain risk factors for kidney disease. Some of these risk factors include high blood pressure, diabetes, and a family history of kidney disease.

For people with an elevated risk of kidney problems, screening with a renal panel may be part of normal health checkups. Screening of this type is not standard in people who do not have risk factors.

A renal panel can be used as a monitoring test if you have had kidney problems in the past or have already had an abnormal renal panel test. If you are receiving treatment for kidney injury or disease, a renal panel may be used to gauge your response to that therapy.

Other Tests Of Kidney Function

The routine kidney blood test is a general marker of kidney function. If the blood test is abnormal it cannot say what is causing the kidney problem. Therefore, if you have an abnormal result you may need further tests to find the cause of a kidney problem. For example: urine tests, other blood tests, scans, X-rays, kidney biopsy, etc.

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Taking An Estimated Glomerular Filtration Rate Test

An estimated glomerular filtration rate test is a type of blood test. The blood sample for the test is taken with a needle that is inserted into a vein in your arm. This routine procedure is usually done at a doctors office, hospital, or laboratory.

For an at-home test, a drop of blood must be taken from your fingertip and applied to a test strip that can be sent to a medical laboratory.

How Is A Creatinine Test Done

Kidney function test

There are two main ways doctors use creatinine tests to measure kidney function:

  • Urine tests. Creatinine clearance can be pinpointed by measuring the amount of creatinine in a sample of pee collected over 24 hours. For this method, you store all your urine in a plastic jug for one day and then bring it in for testing. This method is inconvenient, but it may be necessary to diagnose some kidney conditions.

  • Blood tests.Doctors can estimate GFR using a single blood level of creatinine, which they enter into a formula. Different formulas take into account your age, sex, and sometimes weight and ethnicity. The higher the blood creatinine level, the lower the estimated GFR and creatinine clearance.

For practical reasons, the blood test method for GFR is used far more often than the 24-hour urine collection test for creatinine clearance. But urine collections may still be useful in people who have large muscle mass or a marked decrease in muscle mass.

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How Is A Renal Panel Test Different From An Estimated Glomerular Filtration Rate Test

The renal panel is a broader test than an estimated glomerular filtration rate test, and in some cases, a renal panel involves eGFR.

The estimated glomerular filtration rate is a common method of evaluating kidney function. It can be calculated in several different ways and reflects how much blood is being filtered by the kidneys every minute.

The eGFR is usually determined with a mathematical formula based primarily on the amount of creatinine in the blood. Because creatinine is measured in most renal panels, the test report may also list eGFR. However, the renal panel also measures electrolytes, minerals, and other substances that can reflect the status of the kidneys.

What Do The Results Of My Kidney Function Test Mean

Kidney function test results can tell you whether your kidneys are functioning typically or not. Most function tests look for two measurements:

  • GFR of less than 60 could indicate kidney disease.
  • Urine albumin-to-creatinine ratio of more than 30 milligrams per gram could be a warning sign of kidney disease.

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How Is A Renal Panel Different From A Kidney Profile Test

The renal panel and kidney profile are designed to assess kidney health. However, there are important differences between them.

The renal panel is only a blood test, and it includes a combination of measurements that can vary based on the laboratory.

In contrast, the kidney profile is a standardized series of two different tests. It includes a blood test for the estimated glomerular filtration rate and a urine test to measure albumin and the albumin-to-creatinine ratio.

While eGFR is calculated on some renal panel tests, it is always included in the kidney profile test. The kidney profile also adds a second test component by measuring urine albumin, which can be an indicator of chronic kidney disease.

This specific two-part kidney profile test was formalized in 2018 through collaboration by professional medical organizations, advocacy groups, and laboratories to enhance the detection of kidney disease. When appropriate, the kidney profile can be ordered along with a renal panel to obtain a wider range of measurements related to kidney health.

How Is An Egfr Test Different From A Creatinine Test

Kidney Function (Creatinine Blood Test) : Diagnostic Test

While many eGFR tests estimate GFR using a single creatinine measurement and a complex calculation, eGFR and creatinine are not the same.

Creatinine is a byproduct of normal muscle activity. The kidneys filter creatinine out of the blood so that it can be cleared from the body. If the kidneys are not working properly, though, creatinine levels can rise.

In this way, GFR can be estimated using creatinine levels, but the two do not have a perfectly proportional relationship.

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What Is A Kidney Function Blood Test

The kidney function blood test measures the level of creatinine, urea and certain dissolved salts.

  • Creatinine is a waste product in your body that is made by your muscles. It passes into your bloodstream, and is usually passed out in urine . A high blood level of creatinine indicates that your kidneys may not be working properly.
  • Urea is produced when protein is broken down by your body. Healthy kidneys eliminate more than 90% of the urea your body produces. A high blood level of urea may indicate that you are dehydrated or that your kidneys may not be working properly.
  • Dissolved salts that are routinely measured are sodium, potassium, chloride and bicarbonate. They are sometimes referred to as ‘electrolytes’. Abnormal blood levels of any of these may sometimes be due to a kidney problem.
  • eGFR stands for estimated glomerular filtration rate. Although the level of creatinine in your blood is a useful guide to kidney function, the eGFR is a more accurate measure of how well your kidneys are filtering your blood. Using your blood creatinine, and your age and sex, your eGFR can be calculated by computer and reported with the creatinine blood test.

Why Would I Need This Test

Kidney tests are very important for people who have kidney disease, diabetes, high blood pressure or heart disease. Your doctor might request these tests if:

  • they suspect your kidneys are not working properly
  • you have kidney disease and your treatment is being monitored
  • your doctor is concerned about the levels of potassium or other minerals in your blood
  • you are taking medication that might affect your kidneys

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How Is An Egfr Test Different From A Creatinine Clearance Test

Creatinine is found in both the blood and the urine. In a creatinine clearance test, the levels of creatinine in blood and urine are compared, and this can inform calculations of GFR.

Conducting a creatinine clearance test requires collecting all urine produced over a 24-hour period, which may be inconvenient. Under- or over-collection of urine during this time can significantly alter test results.

Using creatinine clearance for eGFR also tends to overestimate actual GFR and may require additional adjustments in the calculations or in the interpretation of test results.

Does A Lipid Panel Show Liver Function

Blood Test for Kidney Function

Lipids are one of the necessary components which control cellular functions and homeostasis. Liver plays an essential role in lipid metabolism, several stages of lipid synthesis and transportation. Therefore, it is reasonable to expect an abnormal lipid profile in those with sever liver dysfunction.

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What If My Test Results Show Early Kidney Disease

If a test shows irregular results, your healthcare provider will follow up with you about treatment options. You may receive medications to control blood pressure. Or you may follow up with a nephrologist .

If your test results are atypical, your provider will likely order more frequent kidney function tests in the future. Regular testing helps your provider track your health and any underlying conditions.

A note from Cleveland Clinic

Kidney function tests check how well your kidneys are working. Healthy kidneys assist with removing waste from your body. Conditions such as diabetes or high blood pressure can affect your kidney function. You may also need a kidney function test to diagnose or rule out an infection. Kidney function tests include blood tests or urine tests. Typically, your provider gives you your results the same day or within a few days.

Last reviewed by a Cleveland Clinic medical professional on 07/14/2021.


Who Has A Blood Test Of Kidney Function

Routine kidney function is one of the most commonly performed blood tests. It may be done:

  • As part of a general health assessment.
  • If you have suspected low body water content , when the urea level increases.
  • If you have suspected kidney failure. The higher the blood levels of urea and creatinine, the less well the kidneys are working. The level of creatinine is usually used as a marker as to the severity of kidney failure. Creatinine in itself is not harmful but a high level indicates that the kidneys are not working properly. So, many other waste products will not be cleared out of the bloodstream. You normally need treatment with dialysis if the level of creatinine goes higher than a certain value.
  • Before and after starting treatment with certain medicines. Some medicines occasionally cause kidney damage as a side-effect. Therefore, kidney function is often checked before and after starting treatment with certain medicines.

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Are All Renal Panel Tests The Same

It is common for there to be some variation in the individual components of a renal panel based on the specific laboratory that performs your test. However, some test elements, such as the electrolytes, glucose, calcium, phosphorus, and albumin are found on the most common renal panel tests offered by major laboratories.

In addition, your doctor can request that other specific measurements be included with your renal panel. You will see a line item for each component when you review your test report, and your doctor can explain the significance of each component and the results in the context of your health situation.

Cost And Health Insurance

Kidney Function Tests (KFT) – An Overview

The serum creatinine blood test costs around $25, while the creatinine clearance urine test can run from $35 to $65, depending on the lab and its location. While insurance pre-authorization is generally not required, you may want to call in advance to find out how much your copay or coinsurance costs will be.

If you are uninsured, shop around for prices. Generally speaking, independent labs have lower costs. Some of the larger labs may even offer tiered pricing if you meet certain income qualifications. Ask about patient assistance programs designed to help low-income families.

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What Are The Types Of Kidney Function Tests

Your healthcare provider may order one or a few different types of kidney function tests. You may have blood tests for kidney function, such as:

  • Blood urea nitrogen measures nitrogen in your blood.
  • Estimated GFR calculates filtration rates based on your protein levels, age, gender, size and race.
  • Serum creatinine looks for the buildup of creatinine, a waste product from muscle tissue breakdown.

Your healthcare provider may also use 24-hour urine tests, including:

  • Microalbuminuria looks for a specific protein called albumin.
  • Urinalysis evaluates your urine for blood, proteins and function.

What Are The Risks Of A Bun Test

Unless youre seeking care for an emergency medical condition, you can typically return to your normal activities after taking a BUN test. Tell your doctor if you have a bleeding disorder or youre taking certain medications such as blood thinners. This may cause you to bleed more than expected during the test.

Side effects associated with a BUN test include:

  • bleeding at the puncture site
  • bruising at the puncture site
  • accumulation of blood under the skin
  • infection at the puncture site

In rare cases, people become lightheaded or faint after having blood drawn. Notify your doctor if you experience any unexpected or prolonged side effects after the test.

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Are Test Results Accurate

An eGFR test is a straightforward and generally accurate method of assessing kidney function. In the United States, efforts to calibrate and standardize creatinine measurements have improved the dependability of using creatinine levels to estimate GFR.

However, eGFR is not a perfect test, and several factors can affect its accuracy. For example, eGFR calculations based on creatinine levels are only accurate when a person has stable kidney function. The test is generally not useful or recommended in patients with acute illness, including many who are hospitalized or have serious co-existing conditions.

In addition, most eGFR tests are based on creatinine levels, and test accuracy is affected by individual factors that can influence creatinine levels and the calculation of eGFR. Some of these factors include:

To reduce the effects of these individual factors, eGFR may be estimated by measuring a substance called cystatin C instead of creatinine. In some cases, two eGFR calculationsone using creatinine and one using cystatin C or a combination of bothmay be performed. This serves as a type of initial and confirmatory testing that may improve overall accuracy of estimating GFR.

Can I Take The Test At Home

Kidney disease diagnosis

Very few options exist for a complete renal panel test that can be taken with an at-home test kit. Some at-home kidney tests involve taking a fingerstick blood sample at home and sending it to a lab for analysis, but these tests do not include all of the same measurements that are included in a typical renal panel test.

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Questions For Your Doctor About Test Results

When your test results are ready, you can learn more about their significance by discussing them with your doctor. Some questions that you can ask include:

  • Were there any abnormal findings on my renal panel test? If so, what were they?
  • For any abnormal findings, can you explain what might be the cause?
  • Are there any follow-up tests that are warranted based on my renal panel test?
  • Should I take this test again? If so, when?

Test Results And Stages Of Ckd

Your test results can be used to determine how damaged your kidneys are, known as the stage of CKD.

This can help your doctor decide the best treatment for you and how often you should have tests to monitor your condition.

Your eGFR results is given as a stage from 1 of 5:

  • stage 1 a normal eGFR above 90ml/min, but other tests have detected signs of kidney damage
  • stage 2 a slightly reduced eGFR of 60 to 89ml/min, with other signs of kidney damage
  • stage 3a an eGFR of 45 to 59ml/min
  • stage 3b an eGFR of 30 to 44ml/min
  • stage 4 an eGFR of 15 to 29ml/min
  • stage 5 an eGFR below 15ml/min, meaning the kidneys have lost almost all of their function

Your ACR result is given as a stage from 1 to 3:

  • A1 an ACR of less than 3mg/mmol
  • A2 an ACR of 3 to 30mg/mmol
  • A3 an ACR of more than 30mg/mmol

For both eGFR and ACR, a higher stage indicates more severe kidney disease.

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When To Stop Testing For Liver And Kidney Disease

Further tests may be done to determine more precisely the extent of damage. Besides follow-up tests, it should be emphasized that if a particular chemical substance, whether work-related or not, is causing the abnormality in the liver or a kidney function tests, exposure should be stopped to prevent further damage to these organs.

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It is very essential to know the function of kidney and also the process of urine formation to know the rational behind these test and also to interpret the result of these test.

Glomerular Function- Clearance test

The best test to assess glomerular function is Glomerular filtration rate , which is the rate in milliliters per minute at which substances in plasma are filtered through the glomerulus in other words, the clearance of a substance from the blood. The normal GFR for an adult male is 90 to 120 mL per minute.

GFR cannot be measured directly so various substances are used to assess GFR. There are various exogenous and endogenous substances that are used for clearance test. The characteristics of an ideal marker to measure GFR are as follows:

  • Constant rate of production
  • Freely filterable at the glomerulus
  • No tubular reabsorption
  • No extrarenal elimination or metabolism
  • Availability of an accurate and reliable assay
  • For exogenous marker: safe, convenient, readily available, inexpensive, and does not influence GFR

Clearance is the rate at which an indicator substance is removed from plasma per unit concentration specifies a volume from which all of a substance is removed per unit time. For a substance Z cleared by renal elimination:

Cz =UzxV â Pz

Where Cz is the clearance rate of Z substance, Uz is urinary concentration of z, Pz is plasma concentration of Z, and V is urine flow rate.

Inulin Clearance Test
Creatine Clearance test

Factors affecting serum creatine are:

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