Table 1. Effectiveness of quality circles.

First author/year	Study type	Intervention		Effective
		Guideline adherence improved
Hartmann 1995 [68]	Controlled before-and-after	Diabetes type 2		(Yes)
Ioannidis 2007 [71]	Case series	Osteoporosis, pilot		(Yes)
Ioannidis 2009 [73]	Interrupted time series	Osteoporosis		Yes
Mahlknecht 2016 [78]	Case series	Chronic diseases		(Yes)
Elward 2014 [7])	controlled before-and-after	Asthma		(Yes)
Goldberg 1998 [54]	Randomised controlled	Hypertension and depression		No
Lagerlov 2000 [55]	Randomised controlled	Asthma and urinary tract infections		Yes
Schneider 2008 [60]	Randomised controlled	Asthma		No
Wilcock 2013 [64]	Randomised controlled	Dementia		No
Jager 2017 [67]	Randomised controlled	Polypharmacy		No
		Prescription quality improved
Dyrkorn 2016 [77]	controlled before-and-after	for antibiotics		Yes
Welschen 2004 [59]	Randomised controlled	for antibiotics		Yes
Gjelstad 2013 [6]	Randomised controlled	for antibiotics		Yes
Vervloet 2016 [66]	Randomised controlled	for antibiotics		Yes
Rognstad 2013[63]	Randomised controlled	in general, for elderly		Yes
Richards 2003[69]	Historically controlled study	in general		Yes
		Prescription quality improved and/or costs decreased
Wensing 2004 [70]	controlled before-and-after	prescription quality and costs		Yes
Wensing 2009 [7])	controlled before-and-after	prescription quality and costs		Yes
Niquille 2010 [75]	Cohort	prescription quality and costs		Yes
Riou 2007 [72]	Cohort	prescription costs		Yes
		Test ordering quality improved and/or costs decreased
Verstappen 2003 [56]	Randomised controlled	test ordering quality		Yes
Verstappen 2004 [57]	Randomised controlled	test ordering quality		Yes
Verstappen 2004 [58]	Randomised controlled	test ordering quality and cost reduction		Yes
		Patient safety improved
Verbakel 2015 [65]	Randomised controlled	reporting critical incidents		Yes
Zaher 2012 [51]	Systematic review	Behaviour change		Yes

() means that authors report limited validity of the results