C-Peptide and 24-Hour Urinary C-Peptide as Markers to Help Classify Types of Childhood Diabetes

preserved beta-cell function and negative autoantibodies [7] . While a family history of diabetes is rare in youth with T1DM, individuals with MODY and standard T2DM will show a strong family history of T2DM. There are demographic differences in the types of childhood diabetes. Although the incidence of T1DM is higher in white children, the incidence is increasing in black children [8] , and the incidence in Hispanic children of Puerto Rican origin is among the highest in the US [9, 10] . In T2DM, more minority children are affected, with prevalence rates in African-Americans, Mexican Americans, and Native Americans higher than those of Caucasians. The onset of T2DM is common during puberty and may be related to the decline in insulin sensitivity during this period of development [11, 12] . The SEARCH for Diabetes in Youth study [13] has helped to shed further light on the demographic characteristics of American youth diagnosed with MODY. In SEARCH, autoantibody-negative subjects with fasting C-peptide levels >0.8 mg/ml underwent sequencing for MODY mutations. Out of 47 participants, 8% of those tested were found to have a MODY gene mutation. Most of these subjects had been on insulin, and only 3 had a prior diagnosis of MODY [14] . Unlike the classic description of MODY, only half of the participants had a family history of diabetes, and 64% of the SEARCH MODY patients were of a minority ethnicity. The prevalence of different types of diabetes varies widely among regions, countries and populations [1, 2] . Determining the correct type of diabetes during childhood is important to decide the optimal treatment and follow-up care as well as risk factors for families. Historically, children presenting with new diabetes were presumed to have type 1 diabetes (T1DM), originally called juvenile diabetes. Improved classification of diabetes in youth has presented clinicians with diagnostic challenges when evaluating patients. The presence of obesity and acanthosis nigricans is suggestive of type 2 diabetes (T2DM). However, given the rising prevalence of obesity in children, obesity alone does not exclude other types of diabetes. The clinical presentation of children with diabetes may range from mild hyperglycemia to ketoacidosis. Atypical diabetes in African-American children presenting with severe insulin deficiency with a subsequent noninsulin-dependent course has been recognized for several decades [3, 4] . Presently, apart from genetic testing, diagnostic criteria do not always distinguish children with T1DM from maturity-onset diabetes of youth (MODY) or from T2DM. MODY, which represents a small percent of diabetes cases [5] , is often misdiagnosed as T1DM or T2DM. It has recently been determined that MODY is not uncommon in youth with diabetes [6] . Classic MODY was originally described in Caucasians as autosomally inherited with Published online: June 5, 2015 HORMONE RESEARCH IN PÆDIATRICS