INFLUENCE OF CLINICIAN CHARACTERISTICS AND OPERATIONAL FACTORS ON RECRUITMENT OF PARTICIPANTS WITH LOW BACK PAIN: AN OBSERVATIONAL STUDY Daniel Steffens, BPT (Hons), a, b Chris G. Maher, PhD, c Manuela L. Ferreira, PhD, d Mark J. Hancock, PhD, e

Leani S.M. Pereira, PhD, f Christopher M. Williams, PhD, g and Jane Latimer, PhD c ABSTRACT

Objective: The purpose of this study was to identify factors that influence recruitment of patients to an observational study of low back pain (LBP). Methods: From 1147 primary care (first health contact) clinicians initially contacted, 138 (physiotherapists and chiropractors) agreed to participate in a large observational study of LBP and were the focus of the current study. Data were collected pertaining to clinicians' characteristics, operational factors, and the number of patients recruited. The association of a variety of clinician characteristics and operational factors with recruitment rate was determined using a multivariate negative binomial regression analysis. Results: From October 2011 to November 2012, 1585 patients were screened by 138 study clinicians with 951 eligible patients entering the observational study. Clinicians who were members of their professional association had a recruitment rate less than half that of those who were nonmembers (P b .0001). Clinicians who were trained by telephone had a recruitment rate 4.01 times higher than those trained face to face (P b .0001). Similarly, clinicians who referred a larger number of ineligible participants had a slightly higher recruitment rate with an incident rate ratio of 1.04 per ineligible patient (P b .0001). Other clinicians' characteristics and operational factors were not associated with recruitment. Conclusion: This study provides evidence that it is feasible to recruit participants from primary care practices to a simple observational study of LBP. Factors identified as influencing recruitment were professional association (negative association), training by telephone, and referring a higher number of ineligible participants. (J Manipulative Physiol Ther 2015;xx:1-8) Key Indexing Terms: Patient Selection; Back Pain; Primary Health Care; Physical Therapy; Chiropractic

articipant recruitment is one of the most challenging phases of the research process and may cause studies to become unfeasible. 1,2 It is estimated that 85% of

studies do not conclude on schedule due to low participation, 60% to 80% of studies do not meet their chronological endpoint because of challenges in recruitment, and 30% of

a PhD Student, Musculoskeletal Division, The George Institute for Global Health, Sydney Medical School, The University of Sydney, Sydney, Australia. b PhD Student, Department of Physiotherapy, Federal University of Minas Gerais, Belo Horizonte, Brazil. c Professor, Musculoskeletal Division, The George Institute for Global Health, Sydney Medical School, The University of Sydney, Sydney, Australia. d Senior Research Fellow, Musculoskeletal Division, The George Institute for Global Health, Sydney Medical School, The University of Sydney, Sydney, Australia. e Senior Lecturer, Discipline of Physiotherapy, Faculty of Human Sciences, Macquarie University, Sydney, Australia. f Professor, Department of Physiotherapy, Federal University of Minas Gerais, Belo Horizonte, Brazil.

g Research Fellow, Hunter Medical Research Institute, School of Medicine and Public Health, University of Newcastle, Newcastle, Australia. Submit requests for reprints to: Daniel Steffens, BPT (Hons), PhD Student, Musculoskeletal Division, The George Institute for Global Health, Sydney Medical School, The University of Sydney, PO Box M201, Missenden Road, Sydney, New South Wales, 2050, Australia. (e-mail: dsteffens@george institute.org.au). Paper submitted April 11, 2014; in revised form October 1, 2014; accepted October 10, 2014. 0161-4754 Copyright © 2014 by National University of Health Sciences. http://dx.doi.org/10.1016/j.jmpt.2014.10.016

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study sites fail to recruit even a single participant. 1,3,4 Unsatisfactory and/or untimely participant recruitment has serious consequences, leading to an underpowered study, increased resource use and higher costs. 5-7 Importantly, the integrity and validity of the study also rely on obtaining an adequate sample size, and failure to achieve this may cause a study with inconclusive findings. 8 Most previous studies have focused on investigating factors that increase recruitment to randomized controlled trials (RCTs). 3-5,7,9-12 Although RCTs are considered the “gold standard” of study design, 13 not all scientific questions can be answered with this design. Researchers are often interested in questions regarding etiology and prognosis, which may be better answered using an observational study design. Many of the barriers encountered when recruiting participants to RCTs may be similar to those encountered when conducting observational studies; however, factors affecting recruitment to observational studies have not been carefully evaluated. 14 Previous studies have identified reasons clinicians do not enroll eligible patients into clinical trials. 15,16 Although these reasons have been identified predominantly from studies evaluating general practitioners, it is likely that many also apply to allied health practitioners (physiotherapists and chiropractors) who are operating as first contact practitioner for patients presenting with back pain. These reasons include difficulty for practitioners in following the study protocol and completing the recruitment process and patient preference for a certain therapy and difficulties obtaining informed consent from patients. In primary care, these recruitment barriers are often heightened by the clinician's lack of time, which significantly affects their ability to recruit participants. 17 Other factors reported to influence recruitment of patients include the importance of the research question, the simplicity of the research design, and ease of access to treatment. Financial reimbursement has been suggested as a possible factor 10,18,19; however, a recent systematic review found that, in randomized controlled trials, reimbursement for time spent on recruitment is not associated with better recruitment. 20 In addition, it is possible that recruiting from health professionals other than general practitioners such as physiotherapists and chiropractors may produce a different outcome. Regardless, recruitment of patients in primary care remains a significant issue. 5,7 Therefore, studies that use simple recruitment strategies, minimal clinical involvement, and health professionals other than general practitioners may have an advantage in recruiting patients in primary care settings. The reasons certain studies recruit successfully while others do not remain unclear. 21 A better understanding of clinicians' characteristics and the study operational characteristics (eg, method of training and type and number of contacts) may lead researchers to identify study strategies associated with recruitment of a larger number of participants. Therefore, the aim of this study was to identify factors that influence recruitment to an observational study of triggers for low back pain (LBP).

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METHODS Design This observational study investigated primary care clinicians enrolling patients with acute LBP to a case-crossover study (TRIGGERS). Participants were recruited from October 2011 to November 2012. The methods and procedures for recruitment of patients to the TRIGGERS study have been published elsewhere. 22 Participants in the TRIGGERS study (n = 999) were also eligible to enroll in the PACE clinical trial. 23 The PACE clinical trial is a double-blind placebo-controlled trial assessing the effect that paracetamol has on recovery from acute nonspecific LBP. The inclusion criteria for the TRIGGERS and PACE studies were similar; therefore, patients recruited for the PACE clinical trial could also be enrolled in the TRIGGERS study. However, data collected from recruiting clinicians (eg, personal information) and the study operational procedures were different for both studies. Therefore, we reported the data collected from participants who enrolled in the TRIGGERS study only (n = 951). Ethical approval for the study was granted by the University of Sydney Human Research Ethics Committee (protocol no. 05-2011/13742).

Participants TRIGGERS recruited patients seeking care for LBP in primary care clinics across Sydney, Australia. Eligible participants met the following inclusion criteria: (1) comprehends spoken English, (2) main complaint of LBP with or without leg pain (pain between 12th rib and buttock crease), (3) current episode of back pain less than or equal to 7 days duration, (4) new episode (preceded by at least 1 month without LBP), (5) pain of at least moderate intensity during the first 24 hours of this episode (scored on a 6-point scale from none to very severe). The exclusion criterion was confirmed or suspected serious spinal pathology (ie, cancer, fracture, and infection).

Clinician Recruitment Primary care clinicians were recruited for this study. In Australia, primary care clinicians are those registered to provide the first health contact for patients presenting from the community and include general practitioners, practice nurses, psychologists, physiotherapists, chiropractors, and pharmacists. 24 According to the original protocol, general practitioners and pharmacists would be contacted to aid recruitment. However, no attempts were made to recruit general practitioners or pharmacists as adequate numbers of patients were recruited through physiotherapists and chiropractors. In this study, the recruiting primary care clinicians were physiotherapists and chiropractors. Lists of physiotherapists working in Sydney were acquired from their association's Web site. All physiotherapists drawn from the Australian Physiotherapy Association database were

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members of the association. Thirty-five physiotherapists who participated in the study were not members of the Australian Physiotherapy Association and were identified by their colleagues (who were members and received our invitation). The chiropractors were selected from a Google search. A total of 1147 clinicians (39 chiropractors and 1108 physiotherapists) were invited to participate by letter. The letter outlined the study aims, sample size, inclusion/exclusion criteria, and the benefits to the clinician and patient of participation. Interested clinicians were invited to contact the study research team to obtain further information. A study researcher phoned those who responded to further explain the study procedures. Additional training was provided for clinicians interested in recruiting to the study. A total of 138 clinicians (135 physiotherapists and 3 chiropractors) agreed to participate in the study.

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were instructed to fax screening forms for both eligible and ineligible patients to the study researchers as soon as the forms were completed. For those participants agreeing to be involved, consent forms were signed by the participants and clinicians at the participating sites.

Reimbursement Clinicians were reimbursed AU $99 per eligible patient referred to the study. This sum was used to cover the clinician's time spent in recruiting participants, explaining the study to them, and liaising with the study staff. Clinicians were also reimbursed AU $10 per ineligible patient screened, to cover clerical and administration costs. Participants were reimbursed with AU $50 gift card for the time spent answering the questions and to cover the cost of the mobile telephone calls to the researcher. The typical duration of the interview was approximately 30 minutes.

Training Methods After confirming their interest in recruiting, clinicians were offered 2 methods of training: (1) face-to-face training at their clinics or (2) training by a telephone call. The method of training was selected by the clinician.

Face-to-Face Training Clinicians who chose face-to-face training were visited and trained by an experienced research assistant at their own practice. Face-to-face training was supplemented with distribution of a paper copy of the study protocol. Training took around 30 minutes and was done in a group of up to 5 clinicians working at the same practice.

Training by Telephone Call Clinicians who chose telephone training received their hard copy of the study protocol by post approximately 1 week before their telephone training call was scheduled. The calls were made by a research assistant and covered all the topics in the face-to-face training. This training took around 30 minutes and was done individually.

Features Covered in Both Training Methods Irrespective of whether the clinician chose face-to-face or telephone training, the following topics were covered during training: study background, aims, screening form (inclusion/ exclusion criteria—refer to supplementary material for further details), informed consent form, referring patients (providing patient contact information to the research team), terms and conditions, human ethics, and study benefits. Clinicians could opt out at any time during the study period.

Screening Patients Clinicians were asked to screen for eligibility all (ie, consecutive) patients who presented with LBP. Clinicians

Clinician's Characteristics and Data Collection Personal information from the recruiting clinicians was collected, including sex, date of birth, practice details (location/postcode), profession, current position, years of practice, years managing LBP, and whether the clinician was a member of their professional association. All contacts made between the study researchers and the clinicians were entered into a database. Contacts were classified as phone call, letter, or e-mails.

Recruitment Outcome and Recruitment Predictor Variables The recruitment outcome was the total number of eligible patients recruited by each individual clinician by the end of the study. Eligible patients were patients referred by the clinician successfully enrolled in the TRIGGERS study. Although the prediction of recruitment study was conceived after the main TRIGGERS study commenced, the recruitment predictor variables and analysis were defined a priori as presented in the manuscript. Clinicians' characteristics included (1) sex (male/female), (2) age (years), (3) suburb socioeconomic status (determined by comparing the clinic postcode to Australia Bureau of Statistics data on economic advantage and disadvantage by postcode and dichotomized into high ≥ AU $577 or low socioeconomic status b AU $577, based on the average individual weekly income), (4) profession (physiotherapist or chiropractor), (5) clinical experience as practicing clinician (years), (6) clinical experience managing LBP (years), (7) current position (employee or business owner), and (8) professional association membership status (member or not member). Operational factors included (1) training method (face-to-face or telephone call), (2) number of letters (total number of letters sent to the clinician by end of the study), (3) number of telephone calls (total number of phone calls made to the clinician by end of the study), (4) total number of e-mails (total number of e-mails

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Table 1. Characteristics of Recruiting Clinicians Stratified by Recruitment Rate Recruitment Rate per Month a

No. of No. of Eligible Clinicians Participants per (%) Strata (%)

No. of Ineligible Participants per Strata (%)

0 N 0-0.5 N 0.5-1 N 1-2 N2 Total

32 (23.2) 44 (31.9) 27 (19.6) 20 (14.5) 15 (10.9) 138 (100)

8 (1.3) 69 (10.9) 235 (37.0) 158 (24.9) 164 (25.9) 634 (100)

0 (0) 112 (11.6) 162 (17.1) 197 (20.7) 480 (50.6) 951 (100)

a Recruitment rate: total number of participants recruited divided by the number of months in the study.

sent to the clinician by end of the study), (5) total number of contacts (total number of phone calls, letters, or e-mails made and/or sent to the clinician by end of the study), and (6) number of ineligible patients referred (ineligible patients were defined as patients not willing to participate or not fulfilling study inclusion criterion).

Table 2. Clinician's Descriptive Data (n = 138) Variables Sex, male Age Profession, physiotherapist Current position Employee Business owner Clinical experience (y) Clinical experience managing LBP (y) SES of suburb of clinician clinic (high) a Member of their respective association Training method (telephone) No. of letters b No. of telephone call b No. of e-mails b Total no. of contacts (letter/e-mail/telephone call) b No. of ineligible patients b

Mean ± SD or n (%) 73 (53) 42 ± 10 135 (98) 67 (48.5) 71 (51.5) 19.5 ± 10 18.5 ± 9.5 104 (75.5) 103 (74.5) 79 (57.2) 1.1 ± 0.3 0.4 ± 0.3 0.3 ± 0.2 1.8 ± 0.6 4.6 ± 13.9

LBP, low back pain; SES, socioeconomic status. a Suburb socioeconomic status—determined by comparing the clinic postcode to Australia Bureau of Statistics data on economic advantage and disadvantage. b Number of contacts divided by the total time (months) participating in the study.

Data Analysis Analyses were performed using STATA version 12 (College Station, TX). 25 Descriptive statistics were performed to describe the clinician's characteristics and the recruitment rate for the study (defined as the number of patients per month). To evaluate factors that influenced clinicians' recruitment rate, a negative binomial regression analysis was conducted where recruitment rate was the dependent variable and the predictors described above (clinicians and operational characteristics) were independent variables. We used the negative binomial regression analysis because the outcome data were overdispersed (tested by comparing the variance of the data to the mean patient count recruited by clinicians with the likelihood ratio test). Variables with significant univariate associations (P b .2) were entered into a backward stepwise multivariate regression model. Statistical significance was defined as P b .05. As clinicians started the study on different dates, this was accounted for in the analysis by including the number of days in the study as an offset variable in the model. For continuous variables, the incident rate ratio (IRR) can be interpreted as the rate ratio in which the total number of participants is expected to change with a 1-unit increase in the exposure variable. For binary variables, the IRR indicates the expected change in rate of patient recruitment when the variable is positive.

RESULTS From 1147 clinicians initially contacted, 135 physiotherapists (12.2%) and 3 chiropractors (7.7%) agreed to participate. Between October 2011 and November 2012, study clinicians screened 1585 patients. There were 951

eligible patients who entered the study (943 referred by physiotherapists and 8 referred by chiropractors). Table 1 shows participant recruitment rate per month. The overall recruitment rate per clinician was 0.99 patients per month of participation. A minority of study clinicians (n = 15 and all physiotherapists) recruited more than 50% of the participants (n = 480). Thirty-two clinicians (23.2%) did not recruit a single participant during the study period. The top 15 clinicians (clinicians with recruitment rate N 2 patients per month) recruited a median of 24 participants to the study and determined that 164 patients were ineligible. For the low recruiters (clinicians with recruitment rate ≤ 2 patients per month), the median was 3 and determined that 472 patients were ineligible. Clinician's descriptive data are presented in Table 2. Most of the study clinicians were physiotherapists (98%) and had a mean clinical experience managing LBP of 18.5 years. More than half of the clinicians preferred the training to be performed by telephone (57.2%) rather than face to face (42.8%).

Factors That Influenced Recruitment Rate: Univariate and Multivariate Analyses Five clinician factors (sex, age, clinical experience as practicing clinician, clinical experience managing LBP, and whether clinicians were members of their respective associations) and 5 operational factors (training method, number of letters, number of telephone calls, number of contacts—letter/ e-mail/telephone call, and number of ineligible patients referred) revealed a significant association (P b .2) with

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Table 3. Characteristics Associated With Recruitment of Participants, Univariate and Multivariate Analysis (n = 138) Univariate Analysis Factors Clinicians factors Sex, male Age Profession, physiotherapist Current position, employee c Clinical experience, y Clinical experience managing LBP, y SES of suburb of clinician clinic, high d Member of their respective association Operational factors Training method, telephone No. of letters No. of telephone call No. of e-mails Total no. of contacts, letter/e-mail/telephone call No. of ineligible patients

IRR (95% CI)

Multivariate Analysis IRR (95% CI)

2.02 (1.23-3.31) a – 1.04 (1.01-1.06) a – 1.32 (0.80-2.18) – 0.49 (0.08-2.95)



1.03 (1.00-1.05) a – 1.03 (1.01-1.06) a – 1.13 (0.63-2.03)



0.41 (0.24-0.72) a

0.42 (0.25-0.71) b

2.98 (1.84-4.81) a 4.01 (2.38-6.79) b 0.95 (0.89-1.01) a 0.92 (0.82-1.03) a 0.94 (0.79-1.12) 0.97 (0.93-1.01) a

– – – –

1.04 (1.01-1.08) a 1.03 (1.02-1.06) b

With continuous variables, the IRR can be interpreted as the rate ratio in which the total number of participants is expected to change with a 1-unit increase in the exposure variable. With binary variables, the IRR indicates the expected change in rate of patient recruitment when the variable is positive. CI, confidence interval; IRR, Incident rate ratio; LBP, low back pain. a Candidate variables with significant univariate association (P b .2) that entered the multivariate analysis. b P b .0001. c Employee compared with business owner. d Suburb socioeconomic status—determined by comparing the clinic postcode to Australia Bureau of Statistics data on economic advantage and disadvantage, defined as high, greater than or equal to AU $577, or low, less than AU $577.

patient recruitment in the univariate analyses (Table 3) and were candidates for the multivariate analysis. After the backward stepwise regression, 3 variables were remaining in the model. These variables are presented in Table 3 with incident rate ratios. From the clinician's characteristics, only whether clinicians were members of their respective associations was associated (inversely) with recruitment. Clinicians that were members of their respective associations had a recruitment rate less than half that of nonmembers (P b .001). The other 2 variables associated with recruitment were operational factors (training method and number of ineligible patients referred). Clinicians that were trained over the telephone had a recruitment rate 4.01 times greater than those trained face to face. Similarly, clinicians that referred a higher number of ineligible participants had a greater recruitment rate, with incident rate ratio of 1.03 (P b .0001).

DISCUSSION Main Findings Although 41.3% of the clinicians referred 2 or less eligible participants during the study period, we successfully recruited our target sample (n = 951) in a reasonable period of time (13.8 months). The overall recruitment rate was 0.99 patients, per clinician, per month of participation. This provides evidence that, in relatively simple observational studies for LBP, where clinicians are reimbursed for their time, it should be relatively easy to recruit large numbers of participants from primary care. The recruitment success of this study was achieved mainly because 15 primary care clinicians recruited 50.6% of the sample. Among the clinician and operational characteristics investigated, 3 of 14 factors increased recruitment. However, these factors must be considered carefully as they are unsurprising or uninterpretable and the practical implications seem limited. Clinicians that were members of their respective associations had a recruitment rate less than nonmembers conflicts with the view that members who engage in continuing education are more likely to be interested in research. Even in studies that recruit the required sample size in a reasonable time frame, identifying factors that increase recruitment seems challenging, providing a strong case for the urgent need for more studies. This study investigated clinician and operational characteristics and did not assess the characteristics of patients; investigation would require a different study design, that is, one where the characteristics of patients not recruited to the trial are also determined. Patients may decline participation for a variety of reasons including lack of time, lack of understanding of relevance of research question, already anxious about their disease, and others. Understanding better the patient characteristics that predict participation in clinical trials of back pain is an important area for future research.

Comparison With Other Studies Almost universally, recruitment is a challenge. 26 To date, most of the studies investigating factors that influence recruitment of patients in primary care have focused on RCTs. 27 Although many of the challenges encountered with patient recruitment to RCTs are also applicable to observational studies, there may be important differences. 28 There is a significant lack of research on observational study designs. We identified no previous observational studies that reported recruitment rates in primary care and, therefore, could not compare our research findings with previous studies in the field. Findings from our observational study show that clinicians trained by telephone and those who refer ineligible patients throughout the study are likely to have higher recruitment rates. Clinicians who are a member of their professional association are less likely to recruit. These factors have not previously been identified in earlier studies as important to

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recruitment. The latest Cochrane review on strategies to influence recruitment for RCTs found that using telephone reminders, opt-out procedures requiring potential participants to contact the trial team if they did not want to be contacted about a trial, making the trial open rather than blinded, and mailing a questionnaire about home safety to potential participants to an injury prevention trial are factors that improved recruitment in high-quality studies. 5,7 A systematic review reported on a variety of strategies to improve recruitment, the most common being the use of letters, e-mails, and telephone calls to clinicians 3,4; however, similar to our findings, these factors did not significantly increase recruitment.

Limitations and Strengths Some of the strengths of this study are the large number of clinicians that participated in this LBP study and the large number of patients recruited in a short period. These large numbers have enabled us to robustly assess clinician and operational features that, in combination, could lead to successful recruitment of patients to LBP studies in primary care. One weakness of this study was that the factors investigated may apply predominantly to simple observational studies. The simplified design, minimal role required by the study clinicians, and the reimbursement for the time and inconvenience may have contributed to the rapid patient recruitment. The factors associated with recruitment were relatively unexpected. Other clinician characteristics not investigated in this study may be important in influencing recruitment. Although previous studies have described financial reimbursement as important for recruiting clinicians and patients, 9,29 one of the few systematic reviews does not support this. Clinicians who identify reimbursement as a key reason for participating in an RCT are no more likely to recruit patients than those who do not. 20 In the current observational study, financial reimbursement for both clinicians and participants may have influenced recruitment; however, we could not assess this using our current methods. In addition, we could not assess if practice-level characteristics of the providers affected recruitment. Factors such as full-time vs part-time employment status, ownership of multiple practices, employment of other therapists, specialty practices, number of patients treated per week, average duration of consultation session, referral patterns, university affiliation, or other organizational factors were not measured in the current study, and therefore, their effect on patient recruitment remains unclear. Future research might explore the influence of practice characteristics on research recruitment rates. In addition, we did not attend the clinics to observe if the providers were completing participant recruitment as per protocol, and this is a limitation of the study. In this study, the money reimbursed for eligible and/or ineligible patients was to cover clinicians' time spent in

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recruiting participants, explaining the study to them, and liaising with the study staff and clerical and administration costs. The time involved in this process took from 30 to 45 minutes, and the reimbursement valued the clinician's time according to prevailing physiotherapy consultation fees. This strategy was used to ensure that financial reimbursement was not considered an inducement to participate. To minimize errors, eligibility criteria were double checked by a study researcher at the time of the interview. We advised at the initial training and re-enforced throughout the whole study period that all study clinicians should invite all consecutive patients presenting with LBP to the study. If clinicians did not enroll consecutive patients, it would have the potential to include sampling bias in the parent TRIGGERS study. However, we do not believe that this would introduce bias into this study of factors influencing recruitment. In this study, clinicians were not randomly allocated to either training by telephone or by face-to-face visit. The training method was determined by the clinician, and this choice may reflect other confounders in the practice. 30 Clinicians that opted to be trained by telephone may have chosen this due to their busier clinic schedule suggesting contact with a larger number of patients per day than other clinicians and, hence, an increased opportunity to recruit. Regardless, the finding that, in a simple observational study, training of clinicians by telephone appears to be at least as effective as face-to-face training for recruitment has important implications. The training administered by telephone was delivered one to one, as opposed to face-to-face training where 1 or more clinicians (up to 5) were trained at a given time. The individualized training and feedback are effective in improving recruitment. 31 The results that better recruitment is associated with referral of more ineligible participants could be due to a higher overall number of invitations. The relation with professional membership is a complete mystery. The recruitment of primary care clinicians in this study was based on an invitation letter sent by mail, and despite this relatively passive method of recruitment, we could interest a suitable number of clinicians in participating in our study in a relatively short while. Had we used more active methods of encouraging clinicians to participate, such as providing educational seminars and distributing advertisements and newsletters to association databases, we may have had more rapid recruitment of clinicians. Chiropractors were identified by a Google search using the words “Chiropractor Sydney.” The order of appearance in the search may be affected by the search engine optimization, hence, favoring chiropractors who have greater knowledge. However, it remains unclear whether these clinicians would have recruited more subjects to the study. In this study, we contacted the Australian Physiotherapy Association as our primary means of identifying physiotherapists but used a Google search to identify chiropractors. It would have been better to use similar methods to identify both professions. Future studies should use similar methods

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to recruit primary care clinicians. Either, physiotherapy and chiropractic associations should be contacted and using the Google engine to identify nonmember clinicians.

Future Research There is a small but emerging body of literature on factors influencing recruitment. The operational factor (trained by telephone) identified as influencing recruitment in this study may only be appropriate in simple study designs but should be investigated further due to the potential to make clinician recruitment easier and cheaper. To date, there are no studies investigating if primary care clinicians that are members of their respective associations are more or less likely to participate and recruit patients for research. This information would be of value, as clinicians that are members may be easier to contact through their professional association. Future studies should also investigate if practice-level characteristics could influence patient recruitment. In addition, other potentially important factors that could influence recruitment and/or clinicians' behavior, such as number of contacts made with the clinician and reimbursement for time involved for the clinician and administrative staff, need to be considered in future studies. A better understanding of the patient characteristics associated with successful recruitment is also urgently needed. Further research on factors that could maximize recruitment rate must be conducted. Factors that influence patient recruitment in primary care are complex and remain unclear.

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Supervision (provided oversight, responsible for organization and implementation, writing of the manuscript): D.S., C.M., M.F, M.H, L.P, C.W, J.L. Data collection/processing (responsible for experiments, patient management, organization, or reporting data): D.S., C.M., M.F., M.H., L.P., C.W., J.L. Analysis/interpretation (responsible for statistical analysis, evaluation, and presentation of the results): D.S., C.M., M.F., M.H., L.P., C.W., J.L. Literature search (performed the literature search): N.A. Writing (responsible for writing a substantive part of the manuscript): D.S., C.M., M.F., M.H., L.P., C.W., J.L. Critical review (revised manuscript for intellectual content, this does not relate to spelling and grammar checking): D.S., C.M., M.F., M.H., L.P., C.W., J.L.

Practical Applications • This study provides evidence that, in relatively simple observational studies for LBP, it should be relatively easy to recruit large numbers of participants from primary care. • However, even in studies that recruit the required sample size in a reasonable time frame, identifying factors that increase recruitment seems challenging, providing a strong case for the urgent need for more studies in this area.

CONCLUSIONS Although patient recruitment is a challenge, this study of recruiting participants from primary care clinicians for a large observational study of LBP has been positive. Factors identified as influencing recruitment were professional association (negative association), training by telephone, and referring a higher number of ineligible participants. This study has revealed factors associated with recruitment rate, although the ability to predict which clinician will recruit based on operational and clinicians characteristics seems restricted.

FUNDING SOURCES AND POTENTIAL CONFLICTS OF INTEREST No funding sources or conflicts of interest were reported for this study.

CONTRIBUTORSHIP INFORMATION Concept development (provided idea for the research): D.S., CM., M.F., M.H., L.P., C.W., J.L. Design (planned the methods to generate the results): DS., C.M., M.F., M.H., L.P., C.W., J.L.

REFERENCES 1. Blanton S, Morris D, Prettyman M, et al. Lessons learned in participant recruitment and retention: the EXCITE trial. Phys Ther 2006;86:1520-33. 2. Bowen J, Hirsch S. Recruitment rates and factors affecting recruitment for a clinical trial of a putative anti-psychotic agent in the treatment of acute schizophrenia. Hum Psychopharmacol 1992;7:337-41. 3. McDonald A, Knight R, Campbell M, et al. What influences recruitment to randomised controlled trials? A review of trials funded by two UK funding agencies. Trials 2006;7:1-8. 4. Sully BG, Julious SA, Nicholl J. A reinvestigation of recruitment to randomised, controlled, multicenter trials: a review of trials funded by two UK funding agencies. Trials 2013;14:166. 5. Treweek S, Pitkethly M, Cook J, et al. Strategies to improve recruitment to randomised controlled trials. Cochrane Database Syst Rev 2010;(4):MR000013. 6. Mapstone J, Elbourne D, Roberts I. Strategies to improve recruitment to research studies. Cochrane Database Syst Rev 2007;(2):MR000013. 7. Treweek S, Lockhart P, Pitkethly M, et al. Methods to improve recruitment to randomised controlled trials: Cochrane systematic review and meta-analysis. BMJ Open 2013;3:e002360.

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Journal of Manipulative and Physiological Therapeutics Month 2015

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Influence of clinician characteristics and operational factors on recruitment of participants with low back pain: an observational study.

The purpose of this study was to identify factors that influence recruitment of patients to an observational study of low back pain (LBP)...
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