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Living with chronic kidney disease like immunoglobulin A nephropathy (IgAN or IgA nephropathy) can mean a lot of doctor’s appointments, blood tests, and urine tests. Usually, one of these tests will assess your glomerular filtration rate (GFR).
Your nephrology team will explain what these tests mean and why you need to have them. It’s important that you understand what’s going on and what these tests tell you about your body. That way, you can work with your doctors to make informed choices about your healthcare.
Inside your kidneys, you have tiny filters that remove wastes, toxins, and extra fluid from your blood. Your body gets rid of these substances when you urinate. The filters are called glomeruli.
Thus, a test that examines your glomerular filtration rate looks at how well these filters are working. The higher the number, the more they are filtering. If they are filtering well, it means that your kidneys are doing their jobs.
It’s important to note that while it is possible to test for your actual GFR, it is a difficult and expensive test. Instead, most of the time, your doctors will use a formula to estimate your GFR (eGFR). They do this by measuring the level of certain substances in your blood. Since your kidneys usually filter these substances, your doctor can tell how well they are filtering by how much of these are in your bloodstream. The substances they usually look for are creatinine (a waste product of breakdown of muscle tissue and proteins) or cystatin C (a protein produced by most cells of the body). GFR calculation also varies with your age, sex, and body size and is measured in milliliters per minute per 1.73 square meters of body surface area.
Although it is usually a reliable test, an estimated glomerular filtration rate test can be inaccurate, especially in stage 1 and stage 2 of chronic kidney disease. It can also miss changes in your kidney function that happen quickly. Finally, kidney function generally goes down as people get older. This makes it less accurate in people over 70 years old.
Other factors that can make it inaccurate include:
If any of these apply to you, talk to your nephrology team about other ways to test your kidney function.
IgA nephropathy causes damage to your glomeruli, making it a form of glomerulonephritis. Proteins that your immune system uses, called immunoglobulin A, clump up and get trapped in your kidneys. They cause inflammation in the glomeruli, which harms them over time.
Testing your GFR is key to understanding how well your kidneys are working. The more damage your glomeruli experience, the lower your GFR is likely to be.
Because of this, GFR values reflect the percentage of kidney function that you have.
In general, GFR test results mean the following about your kidney function:
Your nephrologist will keep track of your GFR in order to track how well your kidneys are working and how much kidney damage you have. In general, the faster your GFR goes down, the more likely you are to experience IgAN progression.
Researchers are still trying to understand whether knowing how fast your GFR is declining — and treating it with medications that suppress your immune system — can help your long-term prognosis (outlook).
Your healthcare provider may also use your GFR to determine what type of treatment you need for IgA nephropathy, or whether it’s time to change treatments because something isn’t working the way they had hoped. They may also do other tests, like look at your blood urea nitrogen, check for blood and protein in your urine, or even do a kidney biopsy, to get more information. They’ll use these results together to formulate a treatment plan for your kidney needs.
If your GFR drops, there are a few things you can do to support your kidneys. You can’t make IgAN go away, but you can make choices that protect your kidneys as much as possible.
Talk to a healthcare professional about getting better treatment options for IgAN. In large phase 3 clinical trials, some medications were shown to help slow GFR decline in people with IgAN. Only your doctor can tell you for sure if these are good options for you. Reach out to them if you’re concerned about your kidneys or you want to know if these treatment options should be part of your plan.
Hypertension (high blood pressure) can happen when your kidneys are damaged. It can, in turn, lead to more kidney damage. If your blood pressure is high, getting it under control could slow the rate of kidney damage you experience, thus slowing your GFR decline.
Your doctor may prescribe either an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin-receptor blocker (ARB) to help lower your blood pressure. They may also have you limit how much salt you eat, as this can also help with blood pressure problems.
Speaking of lowering salt, that and other dietary changes may help protect your kidneys. You may need to meet with a registered dietitian or other nutrition professional to figure out exactly what you should and shouldn’t eat, given the specifics of your body and how kidney disease is affecting it.
In addition to salt, you may need to limit how much phosphorus, potassium, and protein you consume. You’ll want to make sure you continue getting enough calories and healthy fats while you do that, though. This is where a dietitian can be helpful.
Some medications can put extra strain on your kidneys, especially if they are already damaged. These can include antibiotics, common painkillers called nonsteroidal anti-inflammatories (NSAIDs), some diuretics (water pills), as well as some vitamins, herbs, and supplements that you can purchase over the counter.
Your doctor may give you a list of medications to avoid. In addition, you shouldn’t start taking anything without consulting your kidney team. They may want you to try something else if there’s a risk of kidney damage.
One of the best ways to support your kidneys is to have regular checkups with your nephrologist and to make sure you don’t cancel these unless it’s absolutely necessary. These visits allow you to get personalized kidney care from someone who knows your body and your case. Personalized care means that you won’t get generic solutions, but will instead get the best treatment options for your specific needs, based on how well your kidneys are working and how IgAN is progressing.
On myIgANteam, people share their experiences with IgAN, get advice, and find support from others who understand.
How has your GFR changed over time? Let others know in the comments below.
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