Kidney function tests, also known as renal function tests or kidney panel, play an important role in the diagnosis and treatment of various kidney disorders. People who are at increased risk of kidney disorders due to chronic conditions, family history, or other factors need to get regular kidney function tests.
These are often simple procedures that can provide information about a person’s kidney function and overall health. This article talks about different types of kidney function tests and more.
What are kidney function tests?
As the name suggests, kidney function tests (KFTs) are a series of blood or urine tests performed that can help evaluate how well an individual’s kidneys are functioning. Many of these kidney/renal function tests measure the glomerular filtration rate (GFR) in patients, which is the volume of plasma filtered by the glomeruli (a tiny cluster of looping blood vessels in the kidneys that help clean the blood).
The accuracy of a kidney function test relies on complex techniques and special substances or markers; however, these markers are not commonly used in routine clinical settings. In such scenarios, the blood marker creatinine or serum cystatin C can be used instead. It is important to note that serum creatinine is also influenced by several factors not related to the renal system.
The KFT tests analyse the blood or urine and measure different aspects of kidney function. Generally, doctors order more than one test to assess different aspects of an individual’s kidney function.
Functions of the kidneys in the body
An important part of your urinary and renal systems, the kidneys are situated at the back of your abdomen, just below the ribcage. The kidneys play an important role in filtering the blood, maintaining the acid-base balance in the body, excreting metabolic waste from the blood, and synthesising certain substances, among other things.
Why are kidney function tests recommended?
Chronic conditions such as diabetes and hypertension (high blood pressure) can impair kidney function in affected individuals. The doctor may recommend kidney function tests to monitor how well the kidney is functioning in such scenarios. Additionally, people who have had kidney transplants (donor and receiver both) should ideally have kidney function tests routinely. The two major purposes of KFT tests are to assess kidney diseases and renal function.
Kidney function tests are also recommended to people who experience the following symptoms:
- Haematuria or blood in the urine
- Dysuria or painful urination
- Trouble starting to pee
- Frequent urge to pee
Different types of kidney function tests
Listed below are some of the tests used to measure kidney function:
Blood or serum kidney function tests
Blood urea nitrogen (BUN)
Urea nitrogen is a metabolic waste produced when the protein in food breaks down in the body and is normally removed by the kidneys. Normal BUN levels can range from 7 to 20, and these levels increase when the kidneys are not functioning properly. The BUN levels also depend on the amount of protein one consumes.
The average cost of a BUN test in India can range from INR 100 to INR 200.
Estimated glomerular rate (eGFR)
The kidney filters blood by removing waste and excess water to produce urine, which can be measured by GFR. This kidney function test measures how well the kidneys are able to filter substances such as creatinine and cystatin C from the body.
The eGFR test may produce inaccurate estimates of GFR, especially in early-stage kidney diseases. A person who is over the age of 70, on certain medications, pregnant or has unusual muscle mass, cirrhosis, or nephrotic syndrome may experience inaccurate eGFR test results. The normal eGFR number in adults usually is around 90; anything below 90 can be indicative of kidney problems, especially in individuals who are aged below 60 years.
Patients may be given certain eating or drinking recommendations to prepare for the test. They can resume normal activity after sample collection for the test.
The average cost of an eGFR test in India can range from INR 140 to INR 445.
Serum creatinine
Creatinine is produced by the body as a result of normal wear and tear on muscles, and its levels can vary from individual to individual on the basis of different factors such as age, gender, and body size. If the blood test reveals creatinine levels greater than 1.2 in women and 1.4 in men, it indicates impaired kidney functioning, according to the National Kidney Foundation. If the individual’s kidney disease progresses, their creatinine levels in the blood will continue to rise over time.
The average cost of a serum creatinine in India can range from INR 100 to INR 200.
Urine kidney function tests
(The sample for these tests may be collected over a period of 24 hours, or a spot urine sample may be used.)
Urinalysis
This kidney function test involves a microscopic examination of a patient’s urine sample and a dipstick test, a chemically treated strip. This strip changes colour in the presence of abnormalities such as excess amounts of blood, pus, bacteria, sugar, and protein. The dipstick test can also measure pH and glucose levels in the urine.
A urinalysis is useful in detecting various kidney and urinary tract ailments, including chronic kidney disease (CKD), diabetes, kidney stones, and bladder infections.
The average cost of a urinalysis in India can range from INR 40 to INR 170.(14) (15)
Microalbuminuria
This kidney function test is more specific in nature and can detect small amounts of albumin (a protein) in the urine. People with an increased risk of diabetes or high blood pressure are recommended to have this test if the doctor suspects a false-negative dipstick test for proteinuria.
The average cost of a microalbuminuria in India can range from INR 50 to INR 400.(16)
Albumin-to-creatinine ratio (ACR)
This kidney function test can examine the amount of albumin (the most common type of protein found in urine) in the patient’s urine sample. Normally, individuals excrete very small amounts of protein in their urine. If a person has two positive ACR tests in a span of about 3 months, it is considered an early and sensitive principal marker of kidney damage. An ACR value of 30-300 mg/g indicates moderately increased levels of albumin, and an ACR value of more than 300 mg/g refers to a high elevation of albumin that denotes a progressive decline in GFR.
The average cost of a ACR in India can range from INR 300 to INR 650.(18)
Creatinine clearance
A 24-hour urine sample is analysed for creatinine levels in your blood to determine the amount of waste products the patient’s kidneys can filter out each minute. A creatinine clearance test may be used in conjunction with other kidney function tests.
The average cost of a creatinine clearance test can range from INR 60 to INR 500.(19)
Other kidney function tests
Abdominal ultrasound and CT scan
An imaging test such as an abdominal ultrasound is used to check for any abnormality in the size or position of the kidneys or look for stones or tumours. A CT scan helps the doctor ‘see’ the patient’s kidneys; it may be used to look for structural abnormalities and obstructions. The patient may also be given contrast dye intravenously for a CT scan.
The average cost of an abdominal X-ray can range from INR 300 to INR 500 and from INR 1500 to INR 5000 for an abdominal CT scan.
Kidney biopsy
A kidney biopsy may be recommended after preliminary testing to assess the extent of kidney damage, evaluate why a kidney transplant may not be functioning well, or to identify a specific disease process and how it responds to treatment.
A small needle with a sharp edge is used to perform the biopsy. A trained professional removes a small piece of kidney tissue in a minimally invasive procedure. This sample is then processed in a laboratory, and the results are shared after a week or so.
The average cost of a kidney biopsy can range from INR 5,000 to INR 20,000.
Interpreting results of kidney function test
Kidney function test results may be shared with the patient on the same day or after a few days; the laboratory may also share the kidney function test results with the concerned doctor with an attached summary.
The results of kidney function tests or a kidney panel can reveal any abnormality in the individual’s kidney function and help with diagnosing different kidney ailments. GFR of less than 60 could be indicative of kidney disease, and a urine albumin-to-creatinine ratio (UACR) of more than 30 can be a warning sign of kidney disease.
If the kidney function test results show warning signs of kidney disease, the doctor may recommend some diet and lifestyle changes and follow up with patients with different treatment options if needed. Another kidney function panel will likely be recommended after some time to evaluate any changes in kidney function. Sometimes, the patient may also be referred to a nephrologist or a kidney specialist for further care.
If the kidney function tests are inconclusive or atypical, the patient may be ordered to do a kidney function panel frequently. This can help the doctor evaluate the patient’s kidney function and uncover any underlying conditions.
The bottom line
Regular kidney function tests can help with the early diagnosis of CKD and the treatment or management of other kidney diseases. A kidney specialist or nephrologist may be consulted after receiving kidney function test results to evaluate the prognosis and recommend a suitable care plan.
Kidney function test costs vary based on the type of test recommended by the doctor; KFT test costs can start anywhere from INR 399 and go up to INR 1000 or more, depending on the location and other factors. Health insurance providers may also include kidney function tests in their regular screening plans, along with other tests.
