***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE Primary care physicians are increasingly being asked to participate in postal surveys . Difficulties in achieving adequate response rates among physicians have been reported . We investigated the effect of two low-cost interventions on response to a  primary care physician postal question naire . STUDY DESIGN AND SETTING A 2x2 factorial trial was developed within the context of a national survey assessing views and practice s of physicians regarding prostate-specific antigen testing . We evaluated question naire order ( version 1 : demographics first , version 2 : topic-specific questions first ) and written precontact . A national data base of primary care physicians was compiled . One thous and five hundred ninety-nine physicians were r and omly selected , stratified by health board , and r and omized . RESULTS 47.9 % of eligible physicians completed a question naire . There was a statistically significant 5.1 % higher response rate among physicians receiving version 1 of the question naire than those receiving version 2 ( 50.6 % vs. 45.4 % , P=0.05 ) ; the adjusted odds of response were significantly raised ( odds ratio=1.24 ; 95 % confidence interval=1.01 - 1.54 ) . Precontact result ed in a nonsignificant 3.6 % increase in response ( 49.8 % vs. 46.2 % ; P=0.16 ) . The interventions did not interact . CONCLUSION Ordering question naires with general questions first can significantly increase response rates , whereas precontact can achieve a modest increase . These strategies may enhance response while adding little to the cost of a physician survey OBJECTIVES The effects of incentive size on physicians '  response rates to a mail survey were determined . METHODS One thous and US primary care physicians were assigned r and omly to receive a survey with either a $ 5 bill or a $ 2 bill as an incentive . For each of the two incentive groups , the overall response rate for three mailing waves , the total cost , and the total cost per usable response were measured . RESULTS The response rate among those receiving the $ 5 bill ( 61 % ) was 32 % higher than the response rate among those receiving the $ 2 bill ( 46 % ) ; overall costs were slightly higher in the $ 5 group , but the cost per response for each group was similar ( $ 15.46 versus $ 14.93 ) . For the same cost , a higher response rate could have been achieved in the $ 2 group if costs saved from foregoing the third mailing were instead used to increase the incentive for a portion of the subjects . CONCLUSIONS A $ 5 bill incentive yielded a higher response rate among the physicians in this study than did a $ 2 bill incentive . Moreover , the powerful effect of the incentive size , combined with the consequent decline in the costs of subsequent mailing waves , suggests that re sources in a fixed survey budget are allocated more efficiently to increasing the initial incentive rather than to providing a third wave to nonresponders Background The feasibility of r and omized trials often depends on successful patient recruitment . Although numerous recruitment barriers have been identified it is unclear which of them complicate recruitment most . Also , most surveys have focused on the patients ' perspective of recruitment barriers whereas the perspective of recruiting physicians has received less attention . Therefore , our aim was to conduct a postal survey among recruiting physicians of a multi-center trial to weigh barriers according to their impact on recruitment . Methods We identified any potential recruitment barriers from the literature and from our own experience with a multi-center trial of respiratory rehabilitation in patients with chronic obstructive pulmonary disease . We developed and pilot-tested a self-administered question naire where recruiting physicians were asked to express their agreement with statements about recruitment barriers on a Likert-type scale from 1 ( full agreement with statement = very substantial recruitment barrier ) to 7 ( no agreement with statement = no recruitment barrier ) . Results 38 of 55 recruiting physicians returned question naires ( 69 % response rate ) , of which 35 could be analyzed ( 64 % useable response rate ) . Recruiting physicians reported that " time constraints " ( median agreement of 3 , interquartile range 2–5 ) had the most negative impact on recruitment followed by " difficulties including identified eligible patients " ( median agreement of 5 , IQR 3–6 ) . Other barriers such as " trial design barriers " , " lack of access to treatment " , " individual barriers of recruiting physicians " or " insufficient training of recruiting physicians " were perceived to have little or no impact on patient recruitment . Conclusion Physicians perceived time constraints as the most relevant recruitment barrier in a r and omized trial . To overcome recruitment barriers interventions , that are affordable for both industry- and investigator-driven trials , need to be developed and tested in r and omized trials . Trial registration IS RCT OBJECTIVE Achieving high survey participation rates among physicians is challenging . We aim ed to assess the effectiveness of response-aiding strategies in a postal survey of 1,000 r and omly selected Australian family physicians ( FPs ) . STUDY DESIGN AND SETTING A two × two r and omized controlled trial was undertaken to assess the effectiveness of a mailed vs. faxed prenotification letter and a mailed question naire sealed with a label marked attention to doctor vs. a control label . At the time of our final reminder , we r and omized remaining nonresponders to receive a more or less personalized mail-out . RESULTS Response did not significantly differ among eligible FPs receiving a prenotification letter via mail or fax . However , 25.6 % of eligible FPs whose question naires were sealed with a label marked attention to the doctor responded before reminders were administered and compared with 18.6 % of FPs whose question naires were sealed with a control label ( P=0.008 ) . Differences were not statistically significant thereafter . There was no significant difference in response between FPs who received a more vs. less personalized approach at the time of the final reminder ( P=0.16 ) . CONCLUSION Mail marked attention to doctor may usefully increase early response . Prenotification letters delivered via fax are equally effective to those administered by mail and may be cheaper OBJECTIVE To study the effects of payment timing , form of payment , and requiring a social security number ( SSN ) on survey response rates . DATA SOURCE Third-wave mailing of a U.S. physician survey . STUDY DESIGN Nonrespondents were r and omized to receive immediate U.S.$25 cash , immediate U.S.$25 check , promised U.S.$25 check , or promised U.S.$25 check requiring an SSN . DATA COLLECTION METHODS Paper survey responses were double entered into statistical software . PRINCIPAL FINDINGS Response rates differed significantly between remuneration groups ( χ(3 ) ( 2 ) = 80.1 , p<.0001 ) , with the highest rate in the immediate cash group ( 34 percent ) , then immediate check ( 20 percent ) , promised check ( 10 percent ) , and promised check with SSN ( 8 percent ) . CONCLUSIONS Immediate monetary incentives yield higher response rates than promised in this population of nonresponding physicians  . Promised incentives yield similarly low response rates regardless of whether an SSN is requested Background Surveys of doctors are an important data collection method in health services research . Ways to improve response rates , minimise survey response bias and item non-response , within a given budget , have not previously been addressed in the same study . The aim of this paper is to compare the effects and costs of three different modes of survey administration in a national survey of doctors . Methods A stratified r and om sample of 4.9 % ( 2,702/54,160 ) of doctors undertaking clinical practice was drawn from a national directory of all doctors in Australia . Stratification was by four doctor types : general practitioners , specialists , specialists-in-training , and hospital non-specialists , and by six rural/remote categories . A three-arm parallel trial design with equal r and omisation across arms was used . Doctors were r and omly allocated to : online question naire ( 902 ) ; simultaneous mixed mode ( a paper question naire and login details sent together ) ( 900 ) ; or , sequential mixed mode ( online followed by a paper question naire with the reminder ) ( 900 ) . Analysis was by intention to treat , as within each primary mode , doctors could choose either paper or online . Primary outcome measures were response rate , survey response bias , item non-response , and cost . Results The online mode had a response rate 12.95 % , followed by the simultaneous mixed mode with 19.7 % , and the sequential mixed mode with 20.7 % . After adjusting for observed differences between the groups , the online mode had a 7 percentage point lower response rate compared to the simultaneous mixed mode , and a 7.7 percentage point lower response rate compared to sequential mixed mode . The difference in response rate between the sequential and simultaneous modes was not statistically significant . Both mixed modes showed evidence of response bias , whilst the characteristics of online respondents were similar to the population . However , the online mode had a higher rate of item non-response compared to both mixed modes . The total cost of the online survey was 38 % lower than simultaneous mixed mode and 22 % lower than sequential mixed mode . The cost of the sequential mixed mode was 14 % lower than simultaneous mixed mode . Compared to the online mode , the sequential mixed mode was the most cost-effective , although exhibiting some evidence of response bias . Conclusions Decisions on which survey mode to use depend on response rates , response bias , item non-response and costs . The sequential mixed mode appears to be the most cost-effective mode of survey administration for surveys of the population of doctors , if one is prepared to accept a degree of response bias . Online surveys are not yet suitable to be used exclusively for surveys of the doctor population Background Dealing with heterogeneity in meta-analyses is often tricky , and there is only limited advice for authors on what to do . We investigated how authors addressed different degrees of heterogeneity , in particular whether they used a fixed effect model , which assumes that all the included studies are estimating the same true effect , or a r and om effects model where this is not assumed . Methods We sample d r and omly 60 Cochrane review s from 2008 , which presented a result in its first meta- analysis with substantial heterogeneity ( I2 greater than 50 % , i.e. more than 50 % of the variation is due to heterogeneity rather than chance ) . We extracted information on choice of statistical model , how the authors had h and led the heterogeneity , and assessed the method ological quality of the review s in relation to this . Results The distribution of heterogeneity was rather uniform in the whole I2 interval , 50 - 100 % . A fixed effect model was used in 33 review s ( 55 % ) , but there was no correlation between I2 and choice of model ( P = 0.79 ) . We considered that 20 review s ( 33 % ) , 16 of which had used a fixed effect model , had major problems . The most common problems were : use of a fixed effect model and lack of rationale for choice of that model , lack of comment on even severe heterogeneity and of reservations and explanations of its likely causes . The problematic review s had significantly fewer included trials than other review s ( 4.3 vs. 8.0 , P = 0.024 ) . The problems became less pronounced with time , as those review s that were most recently up date d more often used a r and om effects model . Conclusion One-third of Cochrane review s with substantial heterogeneity had major problems in relation to their h and ling of heterogeneity . More attention is needed to this issue , as the problems we identified can be essential for the conclusions of the review Background Few studies have investigated the effect of small unconditional non-monetary incentives on survey response rates amongst GPs or medical practitioners . This study assessed the effectiveness of offering a small unconditional non-financial incentive to increase survey response rates amongst general practitioners within a r and omised controlled trial ( RCT ) . Methods An RCT was conducted within a general practice survey that investigated how to prolong working lives amongst ageing GPs in Australia . GPs ( n = 125 ) were r and omised to receive an attractive pen or no pen during their first invitation for participation in a survey .  GPs could elect to complete the survey online or via mail . Two follow up reminders were sent without a pen to both groups . The main outcome measure was response rates . Results The response rate for GPs who received a pen was higher in the intervention group ( 61.9 % ) compared to the control group ( 46.8 % ) . This study did not find a statistically significant effect of a small unconditional non-financial incentive ( in the form of a pen ) on survey response rates amongst GPs ( Odds ratio , 95 % confidence interval : 1.85 ( 0.91 to 3.77 ) . No GPs completed the online version . Conclusion A small unconditional non-financial incentives , in the form of a pen , may improve response rates for GPs Background Recruitment and retention of patients and healthcare providers in r and omised controlled trials ( RCTs ) is important in order to determine the effectiveness of interventions . However , failure to achieve recruitment targets is common and reasons why a particular recruitment strategy works for one study and not another remain unclear . We sought to describe a strategy used in a multicentre RCT in primary care , to report research ers ' and participants ' experiences of its implementation and to inform future strategies to maximise recruitment and retention . Methods In total 48 general practice s and 903 patients were recruited from three different areas of Irel and to a RCT of an intervention design ed to optimise secondary prevention of coronary heart disease . The recruitment process involved telephoning practice s , posting information , visiting practice s , identifying potential participants , posting invitations and obtaining consent . Retention involved patients attending review s and responding to question naires and practice s facilitating data collection . Results We achieved high retention rates for practice s ( 100 % ) and for patients ( 85 % ) over an 18-month intervention period . Pilot work , knowledge of the setting , awareness of change in staff and 
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Results Monetary and nonmonetary incentives were more effective than no incentive with monetary incentives having a slightly bigger effect than nonmonetary incentives .
Large incentives were more effective than small incentives , as were upfront monetary incentives compared to promised monetary incentives .
Postal surveys were more effective than telephone or email surveys .
Conclusions GP survey response rates may improve by using the following strategies : monetary and nonmonetary incentives , larger incentives , upfront monetary incentives , postal surveys , pre-contact with a phonecall from a peer , personalised packages , sending mail on Friday , and using registered mail .
Mail pre-contact may also improve response rates and have low costs .
Improved reporting and further trials , including sequential mixed mode trials and social media , are required to determine the effectiveness of recruitment strategies on GPs ' response rates to surveys