Can you tell if little Susie or Johnny is likely to experience diabetes-related kidney problems in later years? Even if the diagnosis of type 1 diabetes is fairly new?
Researchers say “yes,” if the albumin-to-creatinine ratio (ACR) is monitored between one and two-and-one-half years after a diagnosis of type 1 diabetes. Age at diagnosis also is a determining factor, they say.
Elevation in creatinine, which is a normal non-protein component of blood, also signals kidney damage. Normal lab values at Joslin are .50 to 1.4 mg/dl for creatinine and 0 to 20 mcg/mg for a microalbumin-to-creatine ratio. According to Robert C. Stanton, MD, chief of nephrology at Joslin Diabetes Center in Boston, patients are generally started on medication when the microalbuminaria is persistently greater than 20 mcg/mg. If the rate of change in the ACR is only 1 percent per year in timed, overnight samples, do not worry, say researchers who studied more than 500 youths with type 1 diabetes in the United Kingdom and followed up with them for 14 years.
In findings reported in the December 2000 issue of Diabetes Care, people whose ACR increased by a median of 70 percent per year in timed, overnight samples went on to develop microalbuminuria, or dangerous levels of protein in the urine. The median means that half the subjects had less than a 70 percent increase and half had an increase of more than 70 percent.
Of the 459 subjects studied, more than 4.5 percent developed persistent microalbuminuria, while nearly 6 percent had transient or “temporary” microalbuminuria that lasted one year or less.
Both age at diagnosis and HbA1c levels were factors in determining whether a person would develop microalbuminuria, researchers say.
Youths who developed type 1 diabetes before or during puberty were more at risk for kidney failure than whose who were diagnosed after puberty, leading researchers to believe that puberty is a higher risk factor for kidney disease than HbA1c levels. They believe that difficulty in maintaining control during the teen-age years can cause temporary injuries to the kidneys. Those temporary injuries can accumulate and contribute to a higher risk of kidney disease. After puberty began, ACRS increased by a median of 80 percent, compared to a median of 26 percent in those who had not yet reached puberty.
In fact, researchers add, puberty may be more of a determining factor than HbA1c levels, but HbA1c levels still are important. Those who had only temporary bouts of microalbuminuria had an HbA1c that was about 2 percent lower than individuals who had on-going microalbuminuria.
Puberty, researchers say, could be a “stress test” for detecting the first stages of kidney injury because of their observations that the ACR rose progressively during the teen-age years in individuals who developed microalbuminuria.
Between 30 and 50 percent of people with type 1 diabetes are at risk for kidney disease. Genetic factors also are believed to be important in determining susceptibility, researchers say.