Almost all patients with type 1 diabetes mellitus (T1DM) need insulin treatment permanently. For selected patients who are unable to achieve glycaemic targets with subcutaneous (SC) insulin treatment, continuous intraperitoneal (IP) insulin infusion is an third-line alternative.

Previous studies demonstrate that continuous intraperitoneal insulin infusion (CIPII) using an implantable pump device improves glycaemic control and quality of life in patients with 'brittle' T1DM. Nevertheless, literature comparing IP and SC insulin treatment is scarce.

The primary objective of this study is to compare the effects of IP insulin delivery to SC insulin delivery.The null hypothesis (H0) of the current study holds inferiority of CIPII compared to SC insulin regarding long-term glycaemic control. The alternative hypothesis (H1) is the inverse: CIPII is non-inferior to SC insulin. In summary, H0: CIPII is inferior to the SC insulin treatment H1: CIPII is not inferior to SC insulin treatment

This is an investigator initiated, open label and prospective matched-control study with a non-inferiority design. The trial duration is 36 weeks and is conducted in a single-centre (Isala Clinics, Zwolle). If non-inferiority is established superiority analyses are performed.

Case inclusion criteria

• T1DM
• If subjects are on CIPII, they must be included in (8) or
• If subjects are on CIPII, and didn't participate in (8), they must been on CIPII at start of the previous study (8)
• If subjects are on CIPII, they must been on CIPII for the past 4 years without interruptions (>30 days)
• Proper knowledge of the Dutch language.

Case exclusion criteria

• Impaired renal function (plasma creatinine ≥150 µmol/L or glomerular filtration rate as estimated by the Cockcroft-Gault formula ≤50ml/min)
• Cardiac problems (unstable angina or myocardial infarction within the previous 12 months or New York Heart Association class III or IV congestive heart failure
• Mentally handicapped
• Current or past psychiatric treatment for schizophrenia
• Cognitive or bipolar disorder
• Current use or oral corticosteroids or suffering from a condition which necessitated oral or systemic corticosteroids use more than once in the previous 12 months
• Substance abuse, other than nicotine
• Current gravidity or plans to become pregnant during the trial
• Plans to engage in activities that require going >25 feet below sea level
• Any condition that the investigator and/or coordinating investigator feels would interfere with trial participation or evaluation of results.

4.4 Control inclusion criteria

• T1DM
• SC insulin as mode of insulin administration
• If subjects are on SC insulin, they must been on SC insulin for the past 4 years without interruption (>30 days)
• HbA1c at time of matching must be ≥7.0% (53mmol/mol)
• Proper knowledge of the Dutch language.

Control exclusion criteria

• Impaired renal function (plasma creatinine ≥150 µmol/L or glomerular filtration rate as estimated by the Cockcroft-Gault formula ≤50ml/min)
• Cardiac problems (unstable angina or myocardial infarction within the previous 12 months or New York Heart Association class III or IV congestive heart failure
• Mentally handicapped
• Current or past psychiatric treatment for schizophrenia
• Cognitive or bipolar disorder
• Current use or oral corticosteroids or suffering from a condition which necessitated oral or systemic corticosteroids use more than once in the previous 12 months
• Substance abuse, other than nicotine
• Current gravidity or plans to become pregnant during the trial
• Plans to engage in activities that require going >25 feet below sea level
• Any condition that the investigator and/or coordinating investigator feels would interfere with trial participation or evaluation of results.

The study sample consists of the subjects on CIPII, who participated in the crossover study performed by Logtenberg et al. (Diabetes Care 32:1372-1377, 2009) or subjects who already used CIPII at that moment (so, for a minimum of 4 years), and matched controls on SC insulin treatment .

The inclusion and exclusion criteria of the previous study are described in detail in (Diabetes Care 32:1372-1377, 2009). In brief, it consisted of patients with T1DM, low fasting c-peptide concentrations (<0.20 nmol/L), aged 18 to 70 years, treated with MDI or CSII and intermediate or poor glycaemic control; defined as glycated haemoglobin (HbA1c) ≥7.5% (58 mmol/mol) and/or ≥5 incidents of hypoglycaemia (< 4.0mmol/L) per week.

If subjects are on SC insulin, they must be able to 'function' as matched control for CIPII patients. The matching procedure, based on age and gender, will take place after patients are being included in the current study.