[C-peptide as the decisive factor for classification of type 1 diabetes mellitus and type 2 diabetes mellitus].
OBJECTIVE
The main objective was to seek, based on defined groups of diabetics, C-peptide levels on fasting and after stimulation which would help to differentiate diabetes mellitus type 1 from diabetes mellitus type 2 in patients with manifestation of diabetes in adult age. GROUPS: Group A comprised 65 non-obese diabetics type 2 with failure of PAD treatment. Group B included 304 newly manifested diabetics type 1 and 2 aged 31-65 years. Group C was formed by 424 patients with diabetes mellitus type 1 and type 2 with different duration of diabetes.


RESULTS
Group A: mean C-peptide levels on fasting 0.32 and after stimulation with a standard breakfast 0.59 pmol/ml suggest absolute insulin deficiency in type 2 diabetics with failure of PAD treatment. Group B: 29.2% diabetics type 1 had already during manifestation of diabetes C-peptide levels on fasting < 0.43 pmol/ml and 47.9% C-peptide of < 0.6 after a meal. There were 1.9 and 4.9% subjects among type 2 diabetics with such low C-peptide levels. After a six-year follow up the mean C-peptide levels on fasting declined in type 1 diabetics from 0.49 to 0.16 pmol/ml and in patients originally with type 2 diabetes reclassified to type 1 the levels dropped from 0.56 to 0.26 pmol/ml. Group C served as the basic group for statistically (linear regression method) detected discrimination values of C-peptide differentiating diabetes mellitus type 1 and diabetes mellitus type 2--the liminal value being 0.59 pmol/ml on fasting and 1.0 pmol/ml after a meal.


CONCLUSIONS
In clinical practice it is not possible to assess reliably slowly manifesting diabetes type 1 (LADA by age, BMI and compensation of diabetes. Positivity of antiGAD antibodies does not rule out diabetes mellitus type 1. In unequivocal cases the decisive factor is therefore the C-peptide level on fasting and after a meal.
Diabetologické centrum VFN a 1. III. interní klinika, lékarské fakulty UK, Praha.
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Perusicová
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Bárová
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M
Hill
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Masek
D000328:Adult; D000368:Aged; D001323:Autoantibodies / Q000032:analysis; D001324:Autoantigens; D015415:Biomarkers / Q000097:blood; D002096:C-Peptide / Q000097:blood*; D003922:Diabetes Mellitus, Type 1 / Q000175:diagnosis*; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005260:Female; D005968:Glutamate Decarboxylase / Q000276:immunology; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000032:analysis; D008875:Middle Aged; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000032:analysis; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8
D001323:Autoantibodies; D001324:Autoantigens; D015415:Biomarkers; D002096:C-Peptide; D008565:Membrane Proteins; C024211:islet cell antibody; C516862:PTPRN protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D005968:Glutamate Decarboxylase