Comparing measured and reported change in gastrointestinal symptoms after initiation of metformin treatment: a...

The majority of individuals in Sweden with type 2 diabetes have their sole health care provider in primary health care. Metformin treatment often causes gastrointestinal side-effects. Our aim was to construct and validate a questionnaire assessing gastrointestinal symptoms before and after starting metformin treatment for type 2 diabetes.

In the Interaction Between Metformin and Microbiota (MEMO) study, 54 participants rated six gastrointestinal symptoms at baseline and after 2 months of metformin treatment in a questionnaire (measured change, i.e. the difference between assessments at these two time points), as well as direct assessment of perceived change in symptoms after 2 months in a separate validation questionnaire (reported change, i.e. how participants themselves have perceived the change between the same two time points). Spearman's ρ was calculated and reported with its 95% CI.

The agreement between reported and measured change of symptoms, measured as Spearman's ρ, was above 0.4 for 4 out of 6 symptoms (poor appetite 0.60 [95% CI 0.39-0.75], loose stool or diarrhea 0.58 [95% CI 0.37-0.74], flatulence 0.45 [95% CI 0.21-0.64], and abdominal pain 0.45 [95% CI 0.20-0.65]). The agreement was lower for nausea and vomiting, although these were numerically above 75% in agreement, likely due to few symptomatic participants overall.

For common side-effect symptoms associated with metformin treatment, our study shows that symptom change measured as the difference between assessments at two different time-points was in overall agreement, validating the usability of the constructed questionnaire for metformin side-effects.