SAN DIEGO – More than one-third of type 1 diabetes cases from a large pediatric Medicaid population were misdiagnosed as having type 2 diabetes early in management, results from a 10-year analysis showed.
Such misclassification "may be associated with significantly increased risk of life-threatening but potentially preventable acute complications such as diabetic ketoacidosis," Dr. Avnish Tripathi said at the annual scientific sessions of the American Diabetes Association. "These findings have implications for primary health care of diabetes and reiterate the importance of performing laboratory tests such as autoantibody titers and C-peptide levels for establishing type 1 diabetes pathology earlier in the clinical management process."
The increasing prevalence of obesity "is changing the demographics and clinical manifestations of diabetes in children," said Dr. Tripathi, a doctoral candidate in the Arnold School of Public Health at the University of South Carolina, Columbia. "Then there are disease variations, such as double diabetes and ketosis-prone diabetes, which have further complicated the initial pediatric presentation of diabetes in terms of clear classification between type 1 and type 2 diabetes."
Misclassification can occur both ways, he continued. Since pediatric diabetes is traditionally assumed to be type 1, "it may be diagnosed as such even if characteristics point to type 2 diabetes. Because of increased awareness of type 2 diabetes in the pediatric population, type 1 diabetes in overweight or obese patients may be diagnosed as type 2 diabetes."
In an effort to characterize the rates of initial misclassification of type 1 diabetes as type 2 diabetes and to examine the impact of its clinical implications, Dr. Tripathi and his associates analyzed data from 4,070 subjects aged 17 years and younger enrolled in the South Carolina State Medicaid Program who had at least two initial service encounters with an ICD-9 diagnosis of type 2 diabetes between 1996 and 2006. They also evaluated ICD-9 codes for comorbid medical complications such as obesity and dyslipidemia, and for vascular and other complications such as diabetic ketoacidosis.
Of the 4,070 children and adolescents, more than half (57%) were female, 56% were non-Hispanic black, their median age was 8 years, and they were followed for a median of 7 years. Dr. Tripathi reported that 2,489 of the subjects (61%) maintained a diagnosis of type 2 diabetes over time while 39% were later reclassified as having type 1 (misclassification group).
Compared with their counterparts who maintained a diagnosis of type 2 diabetes over the follow-up period, a significantly higher proportion of youth in the misclassification group were treated with insulin (82% vs. 2%, respectively) and went on to develop dyslipidemia (P < 0.001) and hypertension (P = 0.0001).
After accounting for follow-up time and other variables, older age at diagnosis increased the risk of misclassification (odds ratio [OR] 1.66), while being obese or overweight decreased the risk of being in the misclassification group (OR 0.79).
Compared with those who maintained a diagnosis of type 2 diabetes, youth in the misclassification group had a 50-fold increased risk of at least one incidence of diabetic ketoacidosis (OR 49.5), nearly a fourfold increased risk of developing cumulative diabetic neuropathy (OR 3.75), a higher risk of cumulative renal complications (OR 1.27), and a lower risk of developing cardiac conditions (OR 0.81).
Dr. Tripathi also reported that older age was associated with increased risk of cumulative neuropathy (OR 1.79), renal complications (OR 1.17), and cardiovascular complications (OR 1.44).
He acknowledged certain limitations of the study, including ascertainment and information bias due to the use of administrative data, "but we tried to mitigate this by using more than one service encounter and use of concomitant medications to ascertain medical conditions. However, the direction of causality cannot be inferred from our results, and the results cannot be extrapolated to other regions and populations."
Dr. Tripathi said that he had no relevant financial disclosures.