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Factors Related to C-peptide Levels Following Type 1 Diabetes Diagnosis In Type 1 Children

Jan 13, 2018
 

Young patients with low BMIs, C-peptide levels, and significant symptoms at onset of diabetes at higher risk of undergoing rapid C-peptide decline.

C-peptide is one of the most useful markers of insulin secretion and is used to aid in diabetes diagnosis. Children diagnosed with type 1 diabetes mellitus (T1DM) are usually insulin deficient after 2 to 3 years of onset with little to no serum C-peptide. Data on specific clinical factors that affect C-peptide levels is lacking and need to be identified to better manage diabetes. The goal of this retrospective study was to identify clinical parameters that are related to C-peptide levels in children recently diagnosed with T1DM over a 3-year period. Data from a total of 109 children with a new T1DM diagnosis was reviewed at the Pediatric Endocrinology Department of Chonbuk National University Children’s Hospital. 34 children with an age range of 1 to 19 years old met the inclusion criteria and were enlisted in the study.

The patients were divided into two groups based on rapid or slow progression of diabetes. Diabetes progression rate was determined by C-peptide levels three years after diagnosis. Group A, the rapid progression group, included 27 children with C-peptide less than 0.6 ng/ml. Group B, the slow progression group, included 7 children with C-peptide of 0.6 ng/mL or greater. The children were also further divided into 3 groups based on how severe their symptoms were at diagnosis of T1DM. 5.9% of the children were categorized as having only glucosuria with no symptoms. 67.6% had polydipsia, polyuria or weight loss at diagnosis. The third subgroup consisted of children who experienced significant symptoms along with complications like diabetic ketoacidosis.

Characteristics and lab results obtained from the medical records at baseline at 6-month intervals were compared using the Mann-Whitney U test. A correlation analysis was utilized to compare the relation between these clinical parameters and C-peptide levels. Results were given in mean ± standard deviation. Group A patients were found to be younger at the time of diagnosis (A: 9±4.3 years vs. B: 13.6±3.6 years; P=0.013), had a lower BMI (A: 15.5±2.5 kg/m¬2 vs. B: 18.7±3.3 kg/m2; P=0.035), and experienced more severe symptoms than the patients in group B. Glucosuria with lack of symptoms was seen only in group B (28.6%). Difference in C-peptide levels at onset of diagnosis were statistically significant between group A and B (A: 0.5±0.46 ng/mL vs. B: 1.87± 1.08 ng/mL; P=0.001) and at all the 6-month follow-ups.

Among the children in group A, 11 had C-peptide levels of 0.6 ng/mL or higher at the start of diagnosis and by the 3-year mark, all C-peptide levels decreased to less than 0.6 ng/mL. All of the children in group B had C-peptide levels greater than 0.6 ng/mL at the onset of diabetes and at the 3-year period. Through correlation analysis, it was determined that C-peptide levels for all 34 patients were correlated to age and BMI but not with other lab values such as pH, insulin, and HbA1c. More specifically, group A C-peptide levels at onset diagnosis were found to be correlated to age and all follow-up C-peptide levels. In group B, initial C-peptide levels were correlated with HbA1c but not with follow-up C-peptide levels.

This study demonstrated that younger patients initially diagnosed with T1DM, who have lower BMIs, more symptoms and complications, and low C-peptide levels, undergo a decline in C-peptide levels more quickly. Patients who fall into this category should be targeted more aggressively with insulin therapy and treatment should be initiated earlier to help preserve pancreatic beta-cell function. The study did have limitations, however. The study population was small and only included patients from one hospital. Being a retrospective study based on patient medical records, there is potential for errors. Also, data on other factors that can impact C-peptide levels such as infection and puberty was unknown.

Practice Pearls:

  • Clinical parameters with most association to C-peptide levels are age and BMI.
  • Young patients with low BMIs, C-peptide levels, and significant symptoms at onset of diabetes are at higher risk of undergoing rapid C-peptide decline.
  • In this specific patient population, early aggressive insulin therapy should be considered to preserve pancreatic beta-cell function and therefore increase C-peptide levels.

Reference:

Hwang JW, Kim MS, Lee DY. Factors Associated with C-peptide Levels after Diagnosis in Children with Type 1 Diabetes Mellitus. Chonnam Med J. 2017; 53(3): 216-222.

Graciela Nieto, Pharm. D. Candidate 2018, LECOM School of Pharmacy