TABLE 4.

Risk of bias assessment

Author (reference), year	Random sequence generation	Allocation concealment	Blinding	Incomplete outcome data	Selective reporting
Chambers et al (24),1997	Unclear. Allocation described as “random” but no information provided on how sequence was generated	Unclear. No information on whether allocation sequence was concealed	Participants: Low risk. Providers: Low risk. Assessors: Unclear. Telephone calls made by assessors and it is not stated if they were blinded to condition	Low risk	Low risk
Sutters et al (28), 2004	Low risk	Unclear. Allocation by SPSS (IBM Corporation, USA) random number generator, but unclear on whether this sequence was generated at the outset and concealed or completed for each participant	Participants: High risk. Due to nature of condition, parent was aware of assignment. Could have influenced results. Providers: High risk. Same as for participants. Assessors: not applicable; parent completed assessments on own	Low risk	Low risk
Franck et al (25), 2007	High risk. Random allocation sequence was randomly generated for one week time blocks, not per participant. Therefore, participants recruited within a week were not randomly assigned to condition	High risk. Allocation of sequence was revealed after first child in one week block was assigned	Participants: High risk. Due to nature of condition (visible tattoo), parent was aware of assignment. Providers: High risk. Same as above. Assessors: High risk. Same as above	Low risk	High risk: Pain outcomes reported incompletely (no values reported)
Helgadottir (26), 2007	Low risk	Unclear. No information on whether allocation sequence was concealed	Participants: High risk. Providers: Low risk. Assessors: Unclear. Telephone calls made by assessors and it is not stated if they were blinded to condition	Low risk	Low risk
Unsworth et al (30), 2007	Low risk	Low risk	Participants: High risk. Due to nature of condition, parent was aware of assignment. Providers: Unclear. No information provided. Assessors: Not applicable; parent completed assessments on own		High risk: Lack of inclusion of pain intensity
Kankkunen et al (27), 2009	High risk. Alternating sampling and more potential participants chose not to participate in the control group	High risk. Allocation was alternating; thus, was not concealed	Participants: High risk. Allocation was informed before consent. Providers: Unclear. No information provided Assessors: Not applicable; parent completed assessments on own	Low risk	Low risk
Sutters et al (29), 2010	Low risk	Unclear. Allocation by SPSS random number generator, but unclear on whether this sequence was generated at the outset and concealed or completed for each participant	Participants: High risk. Due to nature of condition, parent was aware of assignment. Could have influenced results. Providers: High risk. Same as for participants. Assessors: Not applicable; parent completed assessments on own	Low risk	Low risk
Vincent et al (31), 2012	High risk. All control participants recruited first, followed by all intervention participants	High risk. All control participants recruited first, followed by all intervention participants	Participants: High risk. Due to nature of condition, parent was aware of assignment. Could have influenced results. Providers: High risk. Aware of group assignment due to allocation sequence. Assessors: High risk. Aware of group assignment due to allocation sequence	Low risk	Low risk