Referral Sampling: Using Physicians to Recruit Patients

Abstract

Convenience sampling often is necessary when conducting research where there is no frame for a probability sample. This might include samples of people with rare diseases, persons recovering from compulsive behaviors, or those involved in some stigmatized activity. When there is no reliable list from which to draw a statistical sample, the best alternative may be to rely on sampling by referrals, sometimes called snowball sampling (Welch 1975), respondent-driven sampling (Heckathorn 2002), or multiplicity sampling (Rothbart et al. 1982). Referral sampling usually involves identifying individuals who meet inclusion criteria, gaining their cooperation, and then asking them to recruit additional respondents with the same conditions (Heckathorn 2002). However, professional referral sampling has received less notice as a methodology, but is used in health and mental health research. Professional referral sampling involves selecting respondents through an intermediary who provides professional services to the subject. Intermediaries might include pediatricians (Stille et al. 2007), school nurses (Lee et al. 2009), or substance abuse clinicians (Fals-Stewart et al. 2006). We compare our experiences conducting two surveys depending on referral sampling. In each case, physicians acted as intermediaries, helping identify respondents with specific health conditions. Several related lessons are reported and presented for further hypothesis testing.