Table 4 Barriers and other factors impacting the achievement of a representative sample (n = 20)
Author(s) | Long recruitment(>12 months) | Engagement with ‘hidden’ group | Barriers noted |
|---|---|---|---|
Fenta et al. 2006 [32] | ✓ 12 months | Field-workers spoke the target language | Difficult to identify Ethiopian Muslim names in the telephone directory Potential candidates may have been excluded if they had no telephone, stable address or membership in the Ethiopian organizations used to develop the sample frame |
Silove et al. 2007 [39] | ✗ | Field-workers spoke the target language | Sampling strategy favoured Vietnamese refugees living in ethnically dense areas |
De Maio et al. 2014 [30] G | ✗ | Community consultation during development of design and methodology Community Engagement officers (members of local migrant communities) recruited to advocate for study, assist with recruitment etc. Field-workers spoke the target language Interviews conducted in respondent’s homes | The high mobility of the target sample made obtaining accurate contact information challenging |
McAuliffe 2013 [37] G-Report | ✗ | Bilingual assistants available to assist with survey administration | Participants in initial sample excluded if lived in non-metro areas of target cities, lacked a valid phone number or encountered significant language barriers |
Commissariat for Refugees 2008 [29] G-Report | ✗ | Contact details of refugees living in private accommodation not all available/correct in municipality records – highly mobile refugees may have been excluded. Substitutions identified by “trustees” – no explanation of how these selections were made | |
Citizenship and Immigration Canada 2011 [28] G-Report | ✗ | Promotional materials (posters, FAQ brochures) distributed to service provider organizations to encourage eligible participants to respond | Consent given through the returning of a postal questionnaire. Possible self-selection bias (e.g. higher proportion of university education). Poor health or mental health could have been associated with non-response |
Cochran et al. 2013G/Ao (2016) [23]* | Not reported | Field-workers spoke the target language Interviews conducted in respondent’s homes | Lack of contact information for eligible participants |
Maximova & Krahn 2010 [36] G | ✗ | Refugees without available addresses in the government database were excluded, as were those who had relocated from study site | |
Gerritsen et al. 2006 [33] | ✗ | Field-workers spoke the target language Potential respondents contacted by letter and in person | Recruitment only conducted in municipalities that agreed to provide researchers with contact details of potential participants One third of potential participants had incorrect contact details or were absent when interviewers visited |
Spring et al. 2003 [40] | ✓ 25 months | Field-workers spoke the target language. Interviews conducted in respondent’s homes. Field staff maintained a presence in the communities, including after hours and weekends. Created marketing materials (e.g. posters) and recruited at many varied community events and locations | Limited to one person per household. Analyses indicated some significant differences on outcome variables depending on recruitment strategy |
Bhui et al. 2006 [24] | ✓ 12 months | Researchers of same ethnicity as target population networking with local stakeholders to gain trust. Data collection also at weekends and evenings | Census data in the UK does not include country of origin. Authors note that this makes establishing a reliable sampling frame difficult. It was also noted that research fatigue and a failure to see immediate benefits to health and social status were additional barriers to participating in research |
Bilsborrow et al. 2011 [25] | ✗ | Use of archival census data could not identify recent or highly mobile refugees/migrants, or those living in the country illegally | |
Blight et al. 2006 [26] | ✗ | Attempts made to reduce focus on ethnicity in the questionnaire & cover letter to account for refugees who no longer identify as refugees | Consent given through the returning of the postal questionnaire. Poor health or mental health (such as concentration difficulties) could have resulted in non-completion. |
Heeren et al. 2012 [34] | ✗ | Reasons for non-participation included lack of time, indifference, distrust of researchers. Authors noted that RAS may feel intimidated or fearful of the interview situation, which may remind them of interviews or interrogations with officials in their home country | |
Khavarpour & Rissel 1997 [35] | ✗ | Field-workers spoke the target language | The mailed survey component of the study required participants to supply a postal address. This loss of anonymity was a noted barrier to participation |
Qiu et al. 2012 [38] | ✗ | Recruitment from multiple locations to promote respondent convenience | Identified barrier was that participants generally did not travel far to participate Difficult to obtain the trust of potential seeds in a short time |
Vial et al. 2014 [18] | ✗ | Staff partnered with community organizations and local stores frequented by target population | 21.9% of participants who completed the survey were excluded: approximately half of these did not meet inclusion criteria and others had missing data |
Wylie & Jolly 2013 [19] | ✗ | Multiple methods for seed selection improved access to target group | Seed selection significantly influenced which subgroups within a population were accessed |
Bogic et al. 2012 [27] G | ✓ 22 months | Interviews conducted at multiple sites | Authors suggest that the difficulty in recruiting a representative sample of refugees was linked to the absence of detailed population data in the target countries. The lack of registry data in the UK (compared to Italy and Germany) resulted in variation in recruitment methods across countries, which may have led to non-representative samples |
Dunlavy 2001 [31] G-Thesis | Not reported | Local cultural, community and political organizations assisted with recruitment Interviews conducted in locations convenient to participants Translators available to assist with survey administration | Snowballing methodology naturally excluded those not connected with the social networks targeted in the study |