1. Selection bias: method used to generate the allocation sequence, method used to conceal the allocation sequence. Presence of control, characteristics of participants at baseline, ± 10 sample	2. Performance bias: measures used to blind participants and personnel and outcome assessors, presence of other potential threats to validity. Collection and assessment of speech sample	3. Attrition bias: incomplete outcome data, high level of withdrawals from the study. High dropout rate (above 15%)	4. Detection bias: accuracy of measurement of outcomes, length of follow‐up. Reliable tool used, adequate speech sample, outside laboratory recording, immediate versus longer‐term follow‐up	5. Reporting bias: selective reporting, accuracy of reporting. Use of inferential versus descriptive statistics, pooled or individual reporting	Overall risk of bias. Lower/higher	Detail of concerns
Risk of bias: yes/no/unclear
Allen, 2011	Yes	Yes	No	Yes	Yes	Higher	Small sample, unclear research questions and recruitment justification, poor reporting
Amster and Klein, 2008	Yes	Yes	No	Yes	No	Higher	Small sample, no control, volunteered sample
Andrews et al., 2012	Yes	Yes	Yes	No	No	Higher	Small sample, no control, volunteered sample
Antipova et al., 2008	Yes	Yes	No	Yes	No	Higher	Small sample, no control, volunteered sample
Armson and Stuart, 1998	Yes	Yes	No	Yes	No	Higher	Small sample, experimental design with no follow‐up (FU). Single session tests, Kappa scoring methods not described or reliability/results in detail
Armson et al., 2006	Yes	Yes	No	Yes	No	Higher	Small sample, experimental design with no FU
Armson and Kiefte, 2008	Yes	Yes	No	Yes	No	Higher	Mid‐sized sample experimental design with no FU. First 31 people taken into study
Baumeister et al., 2003	Yes	Yes	Yes	No	No	Higher	Large sample, but no control group. Participants showed different severity of disorder which influenced results. Some participants dropped out or were not assessed at baseline
Beilby et al., 2012	No	Unclear	No	No	No	Lower	Unclear if raters were blinded to time point, 3‐month FU
Berkowitz et al., 1994	Yes	Yes	No	No	No	Higher	Very small sample, no control, no blinding in assessment, self‐reports used
Block et al., 2004	No	No	No	Yes	Yes	Higher	Sample 12, 5‐min conversation 5‐min reading. Unclear who recorded away from clinic. Basic results for post‐treatment periods, 3‐month FU, limited analysis
Block et al., 2005	No	No	No	No	No	Lower	Large sample, self‐report inventory used at 35‐year FU with 87% of sample response rate. Unclear length of speech sample
Block et al., 2006	No	No	No	No	No	Lower	Same study as 2005 paper with further examination of variables
Block et al., 1996	No	No	No	Yes	No	Higher	Larger sample, no dropout, immediate measurement during intervention, experimental setting, 5‐min samples
Blomgren et al., 2005	Yes	Unclear	No	No	No	Lower	Sample 19. Some use of self‐reported outcome measures post‐study. Sample 4 min of speech, unclear if rater blinded, 6‐month FU
Blood, 1995	Yes	Yes	No	Yes	Yes	Higher	Extremely small sample. Flawed recruitment. Use of self‐reported outcomes
Boberg and Kully, 1994	No	Unclear	No	Yes	Yes	Higher	Sample 42, no control. Telephone call sample 2 min. Unclear if raters blind to time point, percentage change reported
Bonelli et al., 2000	Yes	No	No	No	Yes	Higher	Sample of 9 selected from earlier study, no pooling of data reported by individual only
Bray and James, 2009	Yes	Yes	No	Yes	Yes	Higher	Small sample, use of self‐reported outcomes
Bray and Kehle, 1998	Yes	Yes	No	Yes	Yes	Higher	Small sample (4), volunteers. Content of speech sample and listener varied between individuals and time, descriptive data by individual only
Carey et al., 2010	No	No	No	No	No	Lower	20 per trial arm, with 75% loss to FU, 12‐month FU, 10‐min recording via telephone, blinded assessment
Cocomazzo et al., 2012	No	No	Yes	Unclear	No	Lower	12 participants and dropouts, blinded rating, beyond clinic recordings made by participant but asked to make only one, 12‐month FU
Craig et al., 1996	No	No	No	Yes	No	Lower	Larger sample, raters blinded 12‐month FU, 5‐min speech samples
Craig et al., 2002	Yes	Yes	No	Yes	No	Higher	Small sample (6) selected from previous study, 2‐year FU, descriptive data for individuals only, home measure potential for bias
Cream et al., 2009	Yes	No	Yes	Yes	No	Higher	Sample of 10, 5‐min recordings, use of some self‐reported outcomes, 2 dropouts in small sample, blinded assessor, immediate post‐assessment
Cream et al., 2010	No	No	No	No	No	Lower	Randomized sample with acceptable dropout rate, blinded assessment, 6‐month FU
De Veer et al., 2009	Yes	Yes	No	Yes	No	Higher	Selection of potential participants by researchers. No detail of randomization. No measure of fluency, self‐report measures only
Druce et al., 1997	Yes	No	No	Yes	No	Lower	Sample 15 with adequate FU, 2‐min speech sample, raters blinded
Elliott et al., 1998	Yes	Yes	No	No	Yes	Higher	Small sample (5) 5‐min conversation sample, reported by individuals, limited analysis
Femrell et al., 2012	Yes	Yes	Yes	Yes	No	Higher	Sample 10 with 2 loss to FU, 10‐min conversation, assessed by clinician, not blinded
Foundas et al., 2013	No	Unclear	No	Unclear	No	Higher	Sample 24 (10 control) with control and experimental conditions. Immediate outcomes, length of sample not reported. Unclear whether blinded
Franken et al., 1992	No	No	No	Yes	No	Higher	Fair sized sample, (32) 6‐month FU, rating scale used, blinded assessment, control normal speakers, 5‐min recordings, purpose to compare normal to post‐intervention rather than evaluate interventions per se
Franken et al., 2005	No	No	Yes	Yes	No	Lower	Small sample randomized to 1 of 2 arms. Loss to FU, recordings made by parents, blinded assessors
Franklin et al., 2008	No	Yes	No	Unclear	No	Higher	Larger sample, however, participants were not randomized to each condition, assessment carried out by authors not blinded, immediate FU, sample 1500 syllables
Gagnon and Ladouceur, 1992	Yes	Unclear	No	Unclear	Yes	Higher	Small samples used in separate studies. Data presented by individual, lack of clarity regarding data collection and evaluation
Gallop and Runyan, 2012	Yes	Unclear	Unclear	Yes	Yes	Higher	Sample 11 participants no control, no explanation of recruitment criteria, 15‐min telephone samples, not reported if blinded, informal FU
Hancock and Craig, 1998	Yes	No	No	No	No	Lower	Larger sample (77 participants), 12‐month FU. Pseudo‐randomization, 5‐min speech sample, in clinic at distance via phone
Hancock et al., 1998	Yes	No	No	No	No	Lower	Same study as other paper. This paper reports some different outcomes
Hancock and Craig, 2002	Yes	No	No	Yes	No	Lower	Sample (12) selected from earlier study 5‐min only speech sample
Harris et al., 2002	No	No	Yes	No	No	Lower	Small study 29 participants, 6 dropped out (21%)
Harrison et al., 2004	No	No	Yes	No	No	Lower	46 participants, 8 dropped out
Hasbrouck, 1992	Unclear	Yes	No	No	Unclear	Higher	Larger sample, no control, no blinding. Very sparse details given about recruitment, attrition, analysis
Hewat et al., 2006	No	No	Yes	Yes	No	Lower	30 participants recruited, dropout varied from 27% to 40% at different stages of the study, in clinic recording and participant selected recording, rating blinded
Hudock and Kalinowski, 2014	Unclear	No	No	Yes	Yes	Higher	Small study (9) no detail of recruitment, scripted telephone conversations, immediate measurement
Huinck et al., 2006	Unclear	No	No	No	No	Lower	25 participants. No details given about recruitment methods
Ingham et al., 2013	Yes	Unclear	Yes	Yes	No	Higher	Volunteer participants, 9 of 21 did not complete 3‐min monologue, 3‐min conversation. Study purpose to compare normal to PWS however contains before and after data. No detail of whether raters blinded, immediate FU, in‐clinic rating
Ingham et al., 2001	Yes	No	No	Yes	No	Higher	Small sample (5 participants). Use of some self‐reported measures, participants submitted own recording for beyond clinic measure, not detailed whether raters blinded, data reported by participant
Irani et al., 2012	No	Unclear	No	Yes	No	Higher	Mixed method study some self reported measures, use of inferential statistics, small sample (7) little detail of speech sample analysis
Iverach et al., 2009	No	No	No	Yes	No	Lower	Larger sample (64 participants). Use of some self‐reported measures
Jones et al., 2000	No	No	No	No	No	Lower	Large sample (261 children, 4% dropout rate, all explained)
Jones et al., 2005	No	No	No	No	No	Lower	Larger sample (54 children, 13% dropout rate, all explained)
Jones et al., 2008	No	No	Yes	No	No	Lower	This is a 5‐year FU of the earlier study 31% of the original treatment group could not be re‐contacted, and 68% of the control group
Kaya and Alladin, 2012	Yes	No	No	Yes	No	Higher	No comparator group. No detail regarding how stuttering occurrences defined. Immediate assessment at final session
Kaya, 2011	Yes	Yes	No	Yes	No	Higher	Assessment via 2‐min speech sample only, rating scale measure used very limited
Kingston et al., 2003	No	Yes	No	Yes	No	Higher	Larger sample (78 children). Assessment was done by the clinician/researcher with no blinding. Purpose of paper to examine associations (predict treatment time) rather than outcomes
Koushik et al., 2009	No	No	No	No	Yes	Lower	Sample 12 children, 1 dropped out
Koushik et al., 2011	Unclear	Unclear	No	Unclear	No	Higher	Pooled data from 5 clinical sites. Larger sample (134 participants in final analysis). Retrospective file audit. Purpose of study to examine associations rather than evaluate outcomes
Laiho and Klippi, 2007	No	Yes	No	Yes	No	Higher	Sample 21, no control, assessment via video by author, parent‐report data for beyond clinic data. Follow‐up data only parent report
Langevin and Boberg, 1993	Yes	No	Yes	No	No	Higher	Small sample, high dropout rate (21 participants, 11 dropped out) data reported by individual
Langevin and Boberg, 1996	Yes	No	Yes	No	No	Lower	25 in 1 group, 16 in other. Two‐year FU, some loss to FU 2/3‐min samples of speech in clinic and via telephone. Raters probably blinded
Langevin et al., 2006	No	No	No	No	No	Lower	18 participants, no control. Small loss to FU
Langevin et al., 2010	Yes	No	Yes	No	No	Lower	5‐year FU of earlier study
Lattermann et al., 2008	No	No	No	No	No	Lower	Sample 46, blinded rating
Lawson et al., 1993	No	No	No	Yes	No	Higher	Self‐report measures only used, 1‐month FU, some dropout
Leahy and Collins, 1991	Yes	Yes	No	Yes	Yes	Higher	No comparator group, small sample size n = 5 Measures taken by student clinician carrying out intervention. Longer FU only for 2. Reporting by individual only
Lewis et al., 2008	No	No	No	No	No	Lower	Small sample (8 in intervention group, 10 in control group)
Lincoln et al., 1996	No	No	No	Yes	Yes	Higher	Sample of 11, high dropout of potential participants (22 recruited). Some pooled data, some reporting of individuals only, 12‐month FU, parent‐recorded speech data
Lincoln and Onslow, 1997	No	Yes	Yes	Yes	Yes	Higher	Long‐term outcomes of earlier studies. Large initial dropout of potential participants. Parents collected speech sample, parent report questionnaire, descriptive data
Lutz, 2009	Yes	Yes	No	Yes	No	Higher	Findings from a workshop for parents using before and after questionnaires
Mallard, 1998	No	Yes	No	Yes	Yes	Higher	Only measure of success was ‘is child in S&L therapy 1 year after intervention?’ No control group, limited analysis
Menzies et al., 2008	No	No	No	No	No	Lower	Smaller sample—32 participants, 2 dropped out, 16 in each condition
Millard et al., 2008	No	No	Yes	No	No	Higher	Small sample (9) high dropout rate (30%), blinded rating, in clinic assessment, 12‐month FU, data by individual only
Millard et al., 2009	No	No	Yes	No	Yes	Higher	Small sample (10) high dropout rate, parent‐recorded video data. Control group for initial allocation but removed part way, no pooled data descriptive statistics only
Miller and Guitar, 2009	No	No	No	No	No	Lower	Long‐term FU, many participants at minimum level Only 2 dropouts from 15, limited speech sample
Nilsen and Ramberg, 1999	No	No	No	Yes	No	Higher	2 dropouts from 13, use of some scales with limited scoring and analysis, data reported by individual
O'Brian et al., 2003	No	No	No	Yes	Yes	Higher	5 dropout from 30. Reasonable sample, no comparator, participant‐selected recordings, limited statistical analysis
O'Brian et al., 2008	No	No	Yes	No	Yes	Higher	16 of 30 completed. Descriptive analysis
O'Brian et al., 2013	No	No	No	No	No	Lower	No control
O'Donnell et al., 2008	Yes	No	No	No	Yes	Higher	Small sample (7), 5 from previous study who had shown most benefit. Data reported by individual participant
Onslow et al., 1994	Unclear	No	Yes	Yes	No	Higher	High withdrawal for control and intervention, no detail of allocation, audio recordings made by parents, descriptive statistics
Onslow et al., 1990	Yes	Yes	No	No	Yes	Higher	No comparator group, sample size n = 4. Presentation of findings via figures only, no grouping of data
Onslow et al., 1992	Unclear	No	No	No	No	Higher	Focuses on speech naturalness data only comparing PWS and non‐stutterers, no control group, immediate FU, recruitment process unclear
Onslow et al., 1996	Unclear	No	Yes	No	No	Higher	Data reported for only 18 of 32 recruited
Onslow et al., 2002	Yes	No	No	No	Yes	Higher	Small sample (8) 6 of whom in previous studies. For 2 parent‐only recordings. Descriptive data presented by individual only. Purpose of paper to evaluate 1 aspect of intervention outcome
Pape‐Neumann, 2004	Yes	Yes	Yes	Yes	Yes	Higher	This is a pilot study which presents data from a range of interventions
Pollard et al., 2009	No	Yes	No	Yes	No	Lower	Sample 11, no dropout, samples collected at non‐laboratory locations, non‐blinded scoring, immediate outcomes
Ratynska et al., 2012	Yes	Yes	No	Unclear	No	Higher	Large sample found other treatment ineffective, no dropout, no blinding of assessment, incomplete description of data collection
Reddy et al., 2010	Unclear	Unclear	No	Unclear	Unclear	Higher	Small sample (5), limited reporting of findings beyond description of cases
Riley and Ingham, 2000	Unclear	Unclear	No	Unclear	Yes	Higher	Sample 12, pseudo‐randomization, no blinding of assessors, unclear beyond clinic data collection, unclear whether 12 or 6 participants being reported, no reporting of control group outcomes
Rosenberger, 2007	Yes	Yes	Yes	No	No	Higher	Two groups were compared which have an uneven number of participants. Some dropout. Limited blinding and speech measures
Rousseau et al., 2007	No	Yes	No	No	No	Lower	Reasonable sample large proportion of parent‐recorded samples, no analysis of dropouts
Ryan and Van Kirk, 1995	No	Yes	Yes	No	No	Lower	Reasonable sample (24, 20 completed all elements). Pseudo‐randomization, no blinding of speech evaluation
Sicotte et al., 2003	Yes	Yes	No	Yes	No	Higher	Sample 6, rating scales only. Purpose of study to evaluate intervention fidelity rather than outcomes
Smits‐Bandstra and Yovetitch, 2003	Yes	Unclear	No	Yes	No	Higher	Small groups. Each time point presented separately in table form, limited discussion of trends over time. Six participants had received other intervention immediately prior 3‐min sample, assume no blinding, limited statistical analysis
Stewart, 1996	No	Yes	No	Yes	No	Higher	Reasonable sample (15) no blinding of assessment, 3‐min conversation, limited analysis of speech behaviour data, no outside clinic measure, reasonable FU
Stidham et al., 2006	Yes	Yes	No	No	No	Higher	Volunteers recruited, small sample (9), immediate FU, no blinding as assessment, in laboratory evaluation
Stuart et al., 2004	Unclear	Yes	No	No	No	Higher	No detail of recruitment, non‐blinded assessment, in laboratory evaluation, limited speech sample
Stuart et al., 2006	Unclear	Yes (for some elements)	No	Yes	No	Higher	No detail of recruitment, no blinding of assessment for first studies, limited speech sample (300 syllables), reasonable FU, in clinic assessment
Trajkovski et al., 2011	No	No	Yes	Yes	No	Lower	8 of 17 completed, data provided for dropouts, limited pooled data, parent‐collected recordings
Unger, 2012	Yes	Yes	No	Yes	No	Higher	Volunteer participants, reasonable sample, in clinic only, immediate FU, no blinding of assessment 2 × 5‐min monologues
Van Borsel, 2003	Yes	Yes	No	No	No	Higher	Volunteer participants, in‐clinic data, no blinding of recordings, small sample (9)
Von Gudenberg, 2006	Yes	Yes	Yes	Yes	Yes	Higher	No clear description of any measurement, participants or methods used; more a evaluation of collected data up to now
Von Gudenberg et al., 2006	Yes	Yes	Yes	Yes	Yes	Higher	Detailed description of the therapy reasons why this therapy may be effective and a good approach for young adults. However, presented results are outcomes with no clear description of methodology and limited analysis
Wagaman et al., 1993	Yes	No	No	No	No	Lower	Follow‐up data from study
Wagaman et al., 1995	Yes	No	No	Yes	No	Higher	Small sample; no long‐term FU
Ward, 1992	Yes	Yes	No	Unclear	No	Higher	No long‐term outcomes. Reports pilot study findings only, small sample
Wille, 1999	Yes	Yes	Yes	Yes	Yes	Higher	No clear description of method, data collection, data analyses; no reference to other literature
Wilson et al., 2004	No	Yes	Yes	No	Yes	Higher	Small sample, dropouts and lack of data
Woods et al., 2002	Yes	No	No	No	No	Lower	Small sample (8), 1‐month FU. No speech data, study focuses on cognitive and language assessments
Yairi and Ambrose, 1992	No	Unclear	Yes	No	No	Higher	Reasonable sample (27) 2‐year FU, speech sample small (around 500 words), 6 dropout, unclear whether speech assessors blinded, in clinic data
Yaruss et al., 2006	No	Yes	No	Yes	No	Higher	Sample 17, speech rated by clinician, FU up to 2 years with no dropout, at least 200 word sample unclear how collected, limited analysis
Zimmerman et al., 1997	No	Unclear	No	Yes	No	Higher	Small sample (9), no long‐term FU, scripted conversations, unclear if rater blinded