Breath tests cover the fraction of nitric oxide in expired gas (), volatile organic compounds (VOCs), variables in exhaled breath condensate (EBC) and other measurements. For EBC and for , official recommendations for standardised procedures are more than 10 years old and there is none for exhaled VOCs and particles. The aim of this document is to provide technical standards and recommendations for sample collection and analytic approaches and to highlight future research priorities in the field. For EBC and, new developments and advances in technology have been evaluated in the current document. This report is not intended to provide clinical guidance on disease diagnosis and management.Clinicians and researchers with expertise in exhaled biomarkers were invited to participate. Published studies regarding methodology of breath tests were selected, discussed and evaluated in a consensus-based manner by the Task Force members.Recommendations for standardisation of sampling, analysing and reporting of data and suggestions for research to cover gaps in the evidence have been created and summarised.Application of breath biomarker measurement in a standardised manner will provide comparable results, thereby facilitating the potential use of these biomarkers in clinical practice.

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Aim To determine whether the low C-peptide levels (<50 pmol/l) produced by the pancreas for decades after onset of Type 1 diabetes have clinical significance. Methods We evaluated fasting C-peptide levels, duration of disease and age of onset in a large cross-sectional series (n=1272) of people with Type 1 diabetes. We then expanded the scope of the study to include the relationship between C-peptide and HbA1c control (n=1273), as well as diabetic complications (n=324) and presence of hypoglycaemia (n=323). The full range of C-peptide levels was also compared with 1,5-Anhydroglucitol, a glucose responsive marker. Results C-peptide levels declined for decades after diagnosis, and the rate of decline was significantly related to age of onset (P<0.0001), after adjusting for disease duration. C-peptide levels > 10 pmol/l were associated with protection from complications (e.g. nephropathy, neuropathy, foot ulcers and retinopathy; P=0.03). Low C-peptide levels were associated with poor metabolic control measured by HbA1c (P<0.0001). Severe hypoglycaemia was associated with the lowest C-peptide levels compared with mild (P=0.049) or moderate (P=0.04) hypoglycaemia. All levels of measurable C-peptide were responsive to acute fluctuations in blood glucose levels as assessed by 1,5-Anhydroglucitol (P<0.0001). Conclusions Low C-peptide levels have clinical significance and appear helpful in characterizing groups at-risk for faster C-peptide decline, complications, poorer metabolic control and severe hypoglycaemia. Low C-peptide levels may be a biomarker for characterizing at-risk patients with Type 1 diabetes.