The path to an immunoglobulin A (IgA) nephropathy diagnosis can be a long one, involving many tests to assess your kidney function and potentially rule out other conditions. You might start the process of getting an IgA nephropathy diagnosis after noticing signs of blood in your urine or after the results of a routine urine test indicate blood or protein in your urine.

At your first visit, your doctor will usually check your blood pressure, since hypertension (high blood pressure) is a common symptom in people with IgA nephropathy. They’ll also check for signs of edema (swelling), especially in the face or ankles. Based on these findings, your doctor may order more tests to confirm this condition.

Urine Tests

Urine tests require you to give a sample of your urine (pee). Your kidneys filter waste and expel it in the form of urine, so these tests can tell important information about how well your kidneys are working.

Your urine might look red, brown, or frothy with IgA nephropathy, but even urine that looks normal can have microscopic signs of problems with the glomeruli (kidney blood vessels that filter your blood). IgA nephropathy and other glomerular diseases can cause proteinuria (protein in urine) or hematuria (blood in urine).

1. Urinalysis

A urinalysis is often part of routine care and may be the first test to show signs of IgA nephropathy, even if you weren’t being tested for kidney disease. This test is commonly used to screen for many conditions, including infections, kidney problems, and diabetes.

Two substances in the urine can indicate possible IgA nephropathy. Their presence in your urine tells you there may be damage to your glomeruli. The presence of these substances — protein and blood — doesn’t indicate a definitive diagnosis of IgA nephropathy, but you’ll need follow-up testing if your levels are high.

Proteinuria

Proteinuria is a high level of protein in your urine. When the glomeruli are damaged, they no longer work properly to filter your blood and let protein slip through as a result. That’s why proteinuria is so common in IgA nephropathy.

Urine protein tests often look for a specific type of protein called albumin, which usually stays in the blood when the kidneys are working properly. When albumin is present in urine, it can sometimes make urine look foamy.

High levels of protein in your urine can come from other causes, like dehydration or temporary illness, which is why further testing is necessary to see if you have IgA nephropathy.

Treatments for IgA nephropathy often focus on reducing protein in the urine, as the severity of proteinuria is a predictor of kidney failure. If your IgA nephropathy progresses to kidney failure, you’ll need a kidney transplant or lifelong dialysis.

Hematuria

Hematuria is blood in your urine, which you may or may not be able to see depending on the color. As with proteinuria, damaged glomeruli can cause your kidneys to leak blood into your urine. Even if your urine is its typical color, blood cells can be detected under a microscope.

Hematuria can come from other causes like urinary tract infections (UTIs), so you’ll need further tests to confirm if the blood in your urine indicates IgA nephropathy.

2. 24-Hour Urine Study

Your doctor might recommend a 24-hour urine study if they’ve detected protein in your urine. This test involves collecting your urine in a container every time you pee during a 24-hour period. Once the 24 hours are up, you must return the container to the laboratory.

The goal of a 24-hour urine study is to see how much protein you lose through your urine in that time period.

Blood Tests

Blood samples can also be useful tools to help diagnose IgA nephropathy. Your doctor may use blood tests to check the levels of various substances in your blood and evaluate kidney function.

3. Creatinine Blood Test

Creatinine is a waste product that comes from your muscles. Your kidneys usually filter creatinine out of your blood as waste, but when they’re not functioning properly, creatinine can build up in your bloodstream. Serum creatinine is the name of the blood test for creatinine in your blood, which tells your doctor about your kidney function.

High creatinine levels indicate poor kidney function, so they’re a reliable indicator of kidney disease. If your serum creatinine is high, you’ll need more tests to determine if you have IgA nephropathy or another chronic kidney disease.

4. Blood Urea Nitrogen Test

Your doctor might recommend a blood urea nitrogen (BUN) test if you have high levels of creatinine in your blood.

This test measures a waste product called urea nitrogen that normally gets filtered out of your bloodstream by your kidneys. Your body creates urea nitrogen when it processes or breaks down protein.

A BUN test can’t definitively diagnose IgA nephropathy, but your doctor will consider the result when recommending other tests.

5. Cystatin C Test

Cystatin C is a specific protein your kidneys typically filter out of your blood, but it can build up to high levels in your blood if your glomeruli are damaged. Instead of using this number alone, your doctor considers your cystatin C level alongside your serum creatinine to decide which tests come next.

6. Estimated Glomerular Filtration Rate

Your estimated glomerular filtration rate (eGFR) tells you how much blood your kidneys are filtering each minute, which helps indicate your kidney disease progression. Your doctor calculates your eGFR using the result of your serum creatinine test along with your age, race, weight, and gender.

A lower eGFR indicates a later kidney disease stage and low kidney function. Healthy kidneys have an eGFR of 60 or higher, while an eGFR lower than 60 for at least three months means your kidneys are damaged. However, some people with IgA nephropathy still have eGFR within a normal range. Your doctor will recommend additional tests to learn more about your kidney function.

7. Kidney Biopsy To Confirm Diagnosis

Usually, the final and most definitive step in diagnosing IgA nephropathy is a renal (kidney) biopsy. Getting a kidney biopsy is the only way to confirm if you have IgA nephropathy and get a formal diagnosis.

To perform a kidney biopsy, your healthcare provider uses a long needle to remove a small sample of tissue from your kidney. A pathologist then studies that tissue sample under a microscope, which allows them to see tiny deposits of immunoglobulin A inside the glomeruli as well as kidney damage. Immunoglobulin A is a protein in your immune system that builds up in your kidneys and causes the inflammation that damages the glomeruli.

Even if all tests leading up to your kidney biopsy have pointed to kidney disease, a kidney biopsy may reveal that you don’t have IgA nephropathy. Just 10 percent of renal biopsies lead to an IgA nephropathy diagnosis in the United States, compared to 20 percent to 30 percent in Europe and up to 40 percent in East Asia.

Talk to Your Doctor

Talk to your doctor or nephrologist if you’re concerned about your kidney function because you can see signs of blood or protein in your urine. Be sure to let your doctor know if you have risk factors such as a family history of IgA nephropathy or if you have any related conditions, such as hypertension or liver disease. If you’re at a high risk for IgA nephropathy, your doctor might recommend regularly checking your blood or urine for signs.

You can trust your doctor to guide you through the process of diagnosing IgA nephropathy and interpreting the results of each test so you know what they mean for your health. Your healthcare team can also tell you about your treatment options and possible side effects.

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