Background The German guideline recommends trimethoprim (TMP) for the treatment of uncomplicated lower-urinary-tract infections (uLUTI) in primary care. In the authors' research network, the participating general practitioners (GPs) were asked why they prescribe mostly quinolones instead. The GPs stated the perception of a high rate of therapy failure of TMP and strongly rejected the guideline.

Objective To examine prescribing behaviour for uLUTI and whether a practice test of TMP might effect a change in prescribing habits.

Methods The study was conducted using observational and qualitative elements. A first focus-group (n=6) assessed reasons for current prescribing behaviour. In a 3-month practice test, patients with uLUTI were prescribed TMP (150 mg twice for 3 days). In a second focus group, the GPs (n=12) were presented with the results of the practice test.

Results The first focus group revealed that prescribing was mainly driven by former hospital training and what was perceived as common therapy. GPs felt no need to change a successful regimen. In the practice test, TMP had a success rate of 94% (84 episodes of uLUTI). The second focus group revealed that the practice test had strongly changed opinions in favour of TMP. Self-reflection and ownership of data acquisition were seen as major contributions for change in prescribing. After the test period, TMP remained the antibiotic most often prescribed.

Conclusion Internal evidence and peer-group opinion are strong determinants for clinical decisions. A self-conducted practice test, together with self-reflection in a peer group, strongly supports the process of change.