The rate at which patients with Alport syndrome lose their kidney function varies widely between patients and even within the same individual, according to a study in the Canadian Journal of Kidney Health and Disease.
This insight is crucial when studying potential interventions in clinical trials, which tend to observe patients for a short time only, researchers at the University of British Columbia in Canada said. By not taking this variability into account, trial researchers risk erring in their conclusions, the study said.
That study, called, “The Variability of Estimated Glomerular Filtration Rate Decline in Alport Syndrome,” followed a group of 37 patients with Alport syndrome for two years to determine if their disease was progressing, stable, or improving.
To assess the decline in kidney function, researchers repeatedly measured patients’ estimated glomerular filtration rate (eGFR) during the study period. This rate tracks kidney function by measuring the blood that passes through kidney filters called glomeruli.
The patients were listed in a kidney disease clinical information system called PROMIS. The majority (78%) of those studied were men, with a median age of 36.
Analyses showed that the number of patients whose disease was progressing differed depending on the eGFR at the start of the study. A high number of patients whose disease was progressing was seen among those with high kidney function at the beginning of the study, while those with lower eGFR values were stable to a larger extent.
Among those having an eGFR of 45-60 mL/min/1.73 m2, 73.7% were progressing, while 23.6% were stable. In the group with intermediate function and an eGFR of 30-45 mL/min/1.73 m2, 45.6% were progressing and 53.4% were stable. Of those with an eGFR in the lowest range, at 15-30 mL/min/1.73 m2, only 25.7% were progressing, while 54.8% were stable and 19.5% regressed.
The data showed that while some patients had kidney function that declined in a linear fashion, others had an increasingly rapid disease course. Still others had alternating periods of rapid and slow decline over the two-year period; although they had declined, improvement was seen at a later date.
This variability also was seen among members of the same family, which suggests that a specific mutation provides little information about how the disease will progress in an individual.
The findings suggest that clinical trials might need to rely on other markers of disease progression to determine an intervention’s effectiveness.