Retinal thickness may be used to distinguish men with X-linked Alport syndrome from those with a similar but much more benign kidney disease known as thin basement membrane nephropathy, a recent study reports, although differences were not significant enough in women to work as a potential diagnostic aid.
The finding may make it easier to diagnose people with suspected Alport syndrome, its researchers suggested.
Alport can be difficult to distinguish in its earlier phases from other kidney diseases. But the study did not evaluate whether the method might be feasible in people with early-stage disease.
Researchers at the University of Melbourne also reported that men with autosomal recessive Alport syndrome had abnormal retinal thickness, but differences in methods prevented them from drawing firm conclusions. Their study, “Temporal retinal thinning and the diagnosis of Alport syndrome and Thin basement membrane nephropathy,” was published in the journal Ophthalmic Genetics.
Early Alport and thin basement membrane nephropathy look very similar when analyzing kidney tissue samples. While genetic testing is considered the gold standard for diagnosing Alport, the research team thought there may be an easier way of distinguishing between the two.
Eye problems in Alport are common, and recent research suggests that Alport patients have a thinner retina in the parts facing the temples. This can easily be measured using optical coherence tomography (OCT) — a method that is cheap, widely available, and quick to perform.
To test the idea that OCT may aid in Alport diagnostics, the team recruited 19 men and 28 women with X-linked Alport syndrome. Diagnosing women with the condition is often more difficult, particularly if they only have blood urine leakage without other characteristic features.
The study also included four patients with recessive Alport syndrome, five with thin basement membrane nephropathy, and 14 with other kidney diseases.
Men with X-linked disease were in more severe disease stages than women — 74 percent had end-stage kidney failure, compared to 11 percent among women. All recessive Alport patients had kidney failure.
Findings showed that men with X-linked disease had more severe retinal thinning than women with X-linked disease or people with thin basement membrane disease. Women with X-linked Alport did, however, have thinner-than-normal retinas.
The degree of retinal thinning in people with recessive Alport was similar to that seen in men with X-linked disease, but since different OCT scanners had been used, the measurements could not be directly compared, researchers said.
People with other kidney diseases had a similar degree of thinning as that seen in women with X-linked Alport.
Analyses also found thinning was more severe in men with X-linked Alport who had an early onset kidney failure.
Researchers did not assess if the degree of retinal thinning was linked to the severity of kidney disease in patients, so it is not known if the method is equally valuable in detecting early-stage Alport.