Significance of fructosamine in the diagnosis of carbohydrate metabolism disorders in children with cystic fibrosis

Abstract

Introduction. Cystic fibrosis associated (related) diabetes mellitus (CFDM) is one of the most common severe complications of cystic fibrosis. Today, the issue of the goodness of a single measurement of fasting blood glucose, glycated hemoglobin and fructosamine to assess the degree of carbohydrate metabolism disorders in children with cystic fibrosis is a subject of debate. The gold standard for diagnosing carbohydrate metabolism disorders (impaired fasting glycemia, various pre-diabetic conditions, diabetes mellitus) is the oral glucose tolerance test. Data about the diagnostic value of fructosamine for predicting CFDM aren’t dispositive. No credible studies of fructosamine in children with cystic fibrosis have been found in the Russian medical literature.Aim. To determine the diagnostic informative value of the blood fructosamine and other single-measured glycemic marker levels in the early diagnosis of carbohydrate metabolism disorders at the pre-diabetes stage in children with cystic fibrosis.Materials and methods. The results of laboratory tests and instrumental examinations of 87 children with cystic fibrosis aged 5–18 years were reviewed. A cross-sectional study of fructosamine, fasting blood sugar and glycated hemoglobin level (some patients underwent an oral glucose tolerance test), and liver fibroelastometry were also performed.Results and discussion. An increase in the fructosamine level was observed, which indicates a possible CFDM in children (p = 0.049): CFDM is highly likely, if the level of fructosamine is ≥255.5 µmol/l (reference ranges for children are 272–285 µmol/l; sensitivity = 57.1%, specificity = 85.2%). It has been found that children with cystic fibrosis and liver cirrhosis have increased fructosamine levels: cut-off = 253.0 µmol/l (Sn – 70.0%, Sp – 85.2%).Conclusion. The fructosamine level, a single determination of fasting blood glucose and glycated hemoglobin are not informative markers for the diagnosis of pre-diabetic conditions in cystic fibrosis in children. It is important to bear in mind that concomitant liver cirrhosis can affect the fructosamine levels. CFDM can be diagnosed at the lower fructosamine level, despite the generally accepted ranges.