Avilés 1999.
| Methods |
Parallel randomised controlled clinical trial Randomisation ratio: 1:1 Superiority design |
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| Participants |
Inclusion criteria: type 2 diabetes diagnosed after 30 years of age and treated for at least 2 years with at least 50 units of insulin per day, age at enrolment younger than 70 years and HbA1c level ≥ 8%. Exclusion criteria: pregnant women; women trying to become pregnant; patients with a serum creatinine concentration greater than 132.6 mmol/L (1.5 mg/dL) or hepatic enzyme levels greater than twice the upper limit of normal; and patients with medical conditions that could promote lactic acidoses such as renal or hepatic disease, congestive heart failure or chronic obstructive pulmonary disease. Diagnostic criteria: not stated |
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| Interventions |
Number of study centres: 1 Treatment before study: insulin: intervention 96.2 ± 44.9 U/day, control 96.9 ± 43.3 U/day Titration period: 8 weeks |
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| Outcomes |
Outcomes reported in abstract of publication: Primary outcome(s) (as stated in the publication): glycaemic control (HbA1c, fasting plasma glucose), C‐peptide, body weight, lipids, insulin dose, adverse events (hypoglycaemia) |
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| Study details |
Run‐in period: 8 weeks to titrate metformin in maximal dosage Study terminated early (for benefit/because of adverse events): no |
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| Publication details |
Language of publication: English Funding source: Bristol‐Myers‐Squibb Publication status: peer‐reviewed journal |
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| Stated aim of study | Quote from publication: "To evaluate the efficacy of metformin in combination with insulin in patients with type 2 diabetes mellitus poorly controlled with insulin therapy alone". | |
| Notes | ||
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Unclear risk | Comment: not possible to judge whether the sequence generation was adequate |
| Allocation concealment (selection bias) | Unclear risk | Comment: not possible to judge whether the allocation to the intervention and control group was concealed |
| Blinding of participants and personnel (performance bias) Adverse events | Low risk | Quote from publication: "Patients who met the inclusion criteria were randomly assigned in a double‐blind fashion to receive metformin or placebo in addition to their current insulin therapy" |
| Blinding of participants and personnel (performance bias) HbA1c, FPG, lipids | Low risk | Quote from publication: "Patients who met the inclusion criteria were randomly assigned in a double‐blind fashion to receive metformin or placebo in addition to their current insulin therapy" |
| Blinding of participants and personnel (performance bias) Insulin dose | Low risk | Quote from publication: "Patients who met the inclusion criteria were randomly assigned in a double‐blind fashion to receive metformin or placebo in addition to their current insulin therapy" |
| Blinding of outcome assessment (detection bias) Adverse events | Unclear risk | Comment: it is unclear if the outcome assessor were blinded |
| Blinding of outcome assessment (detection bias) HbA1c, FPG, lipids | Unclear risk | Comment: it is unclear if the outcome assessor were blinded |
| Blinding of outcome assessment (detection bias) Insulin dose | Unclear risk | Comment: it is unclear if the outcome assessor were blinded |
| Incomplete outcome data (attrition bias) Adverse events | Low risk | Comment: in table 3 of the article the incidence of adverse events is listed for both groups |
| Incomplete outcome data (attrition bias) HbA1c, FPG, lipids | Low risk | Comment: data were collected, analysed and reported |
| Incomplete outcome data (attrition bias) Insulin dose | Low risk | Comment: was reported |
| Selective reporting (reporting bias) | Low risk | Comment: data on blood pressure, medical history and the physical examination is not reported. However this is not likely to bias the results of the other outcomes |
| Other bias | Low risk | Comment: no incomplete outcome data (attrition bias) Diabetes‐related mortality |