An expert in chronic kidney disease (CKD) provides a recap of data, recently released at AMCP, around the estimate of the US incident population of IgA nephropathy.
Robert Toto, MD: The poster N5 was focused on determining the incidence of IgA nephropathy in the United States. This was a meta-analysis that included a variety of sources to evaluate. The main ones they used were MEDLINE, which is PubMed; Embase; and they also used Cochrane databases to find these data. Then from those databases they came up with 74 studies that were reporting estimated rates of IgA nephropathy.
What they found was an incidence rate of about 1.29 per 100,000, which translated into a relatively low rate. One thing they concluded was there are not a lot of data. To me there’s a lot of uncertainty here on the actual rate. Although they have a good rational for how they came up with that estimate, the problem is that the studies they had were really rather incomplete. The studies were mixed; the ones that reported the rates were varied in terms of how long the patients had been followed. I think from this poster, the conclusion is that we need better data than we have from what’s in the literature. There’s not a systematic registry, if you will, of patients with IgA nephropathy.
The other problem, which they don’t talk about here but I’m certain they would encounter when they’re looking at these studies, is that IgA is probably under-reported. They are forced to look at kidney biopsies because that’s how you make the diagnosis of IgA nephropathy. A lot of patients with IgA nephropathy are probably not getting a biopsy. I say that because there are nephrologists who have patients who have the signs and symptoms of IgA nephropathy, but they don’t do a biopsy of the kidney and just assume that they have IgA nephropathy. Or they have patients who have signs and symptoms of IgA nephropathy—and this is the population I’m talking about—and the [nephrologists] don’t make a diagnosis of IgA nephropathy because they don’t biopsy the patient. There are patients who have blood cells in the urine or protein in the urine, which are the major manifestations of IgA nephropathy, but they never undergo a kidney biopsy. So we’re missing reports of people who have kidney biopsies, and therefore I think, and this isn’t so much a criticism of the authors, but just a criticism of the state of the art, that we don’t have good data to really make an accurate estimate of the incidence of IgA nephropathy. I’m concerned that what this abstract is telling us is that we need more data.
I think it’s likely that the N5 abstract is pointing to the fact that we don’t really know the true incidence of IgA nephropathy in the US. I suspect that it’s higher than what they were able to observe in the abstract simply because they have limited information in order to come to the calculation of 1.29 per 100,000 incidences. I think it’s an important poster because it points to an area of needed research to help better understand this. The reason this is important is that IgA nephropathy can progress to kidney failure. It’s not a necessarily benign disease.
More importantly is that there is no specific treatment that we know of for IgA nephropathy, and there are no FDA approved drugs to treat IgA nephropathy yet. There are studies ongoing to try to find drugs that could ultimately be approved by the FDA for treatment of IgA nephropathy, but we don’t have any right now. That isn’t to say there aren’t people who are being treated. But there haven’t been the kind of rigorous studies done with a particular agent to demonstrate the efficacy and safety of that agent in IgA nephropathy.
Transcript edited for clarity.