Do type 2 diabetes mellitus patients included in randomised clinical trials differ from general-practice patients? A cross-sectional comparative study.

Clarisse Dibao, Amandine Dugard, Bruno Giraudeau

Keywords: Diabetes Mellitus - randomised trial - comparability

Background:

General practitioners frequently question the applicability of randomised controlled trial results to the primary care population. Patients encountered in general practice such as older people or those with multimorbidities are frequently excluded from randomised controlled trials.

Research questions:

Are the characteristics of type 2 diabetes mellitus patients in general practice comparable to those included in randomised controlled trials on which clinical practice guidelines are based ?

Method:

Cross-sectional comparative study. We asked to general practitioners from 3 French Departments to identify the 15 type 2 diabetes mellitus patients they most recently saw in consultation. In parallel, we selected randomised controlled trials included in the Cochrane systematic review on which the clinical practice guidelines for type 2 diabetes mellitus were based.
Characteristics of general-practice patients were extracted from medical records by a unique observer. The same baseline characteristics of patients included in randomised controlled trials from the Cochrane systematic review were extracted and meta-analysed. We assessed standardised differences between these two series of baseline characteristics. A difference greater than 0.10 in absolute value was considered meaningful.

Results:

45 general practitioners included 675 type 2 diabetes mellitus patients, and data were collected from 23 randomised controlled trials, corresponding to 36,059 patients. General-practice patients were older than randomised controlled trial patients (mean [SD] 68.8 [1.1] vs 59.9 years [standardised difference 0.8]) and had higher body mass index (mean [SD] 31.5 [6.9] vs 28.2 kg/m2 [standardised difference 0.5]) but smoked less (11.0% vs 29.3% [standardised difference -0.6]). They more frequently used antihypertensive drugs (82.1% vs 37.5% [standardised difference 1.2]) but less frequently had myocardial infarction (7.6% vs 23.1% [standardised difference -1.1]).

Conclusions:

Type 2 diabetes mellitus patients cared for in general practice differ in a number of important aspects from patients included in randomised controlled trials on which clinical practice guidelines are based.

Points for discussion:

What implications for future research in primary care ?

What recommendations for guidelines ?

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