Population- and Community-based Recruitment of African Americans and Latinos

The San Francisco Bay Area Lung Cancer Study

Daramöla N. Cabral1 , Anna M. Nápoles-Springer2, Rei Miike3, Alex McMillan4, Jennette D. Sison3, Margaret R. Wrensch3, Eliseo J. Pérez-Stable2 and John K. Wiencke3

1 Northern California Cancer Center, Union City, CA.
2 Center for Aging in Diverse Communities, Medical Effectiveness Research Center for Diverse Populations, Division of General Internal Medicine, Department of Medicine, University of California San Francisco, San Francisco, CA.
3 Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, CA.
4 Biostatistics Core, University of California San Francisco Cancer Center, San Francisco, CA.

Received for publication September 27, 2002; accepted for publication January 24, 2003.


    ABSTRACT
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Empiric data on recruitment of minorities into clinical or population studies are limited. The authors evaluated population- and community-based recruitment methods in a 1998–2001 case-control study of lung cancer among African Americans and Latinos. For lung cancer cases in the San Francisco Bay Area of California, rapid case ascertainment by the tumor registry combined with telephone screening identified 470 (9%) African Americans and 262 (5%) Latinos. When random digit dialing (RDD) and Health Care Financing Administration (HCFA) records failed to yield adequate numbers of controls in appropriate age-gender-ethnicity groups, community-based recruitment methods were used. Demographic characteristics and behavioral and occupational risk factors for controls, by recruitment method, were compared with those for lung cancer cases to evaluate potential bias. The average numbers of hours spent per control recruited were 18.6 for RDD, 11.4 for HCFA, and less than 1 for the community-based methods. The prevalence of smoking-related lung cancer risk factors was significantly higher among African-American community-based controls than for those identified through RDD (p < 0.005). Compared with HCFA controls, Latino RDD controls reported significantly higher cumulative smoking exposure (p < 0.05). Further assessment of strategies for successful recruitment of minority participants into epidemiologic studies is warranted.

case-control studies; epidemiologic methods; ethnic groups; investigative techniques

Abbreviations: Abbreviations: HCFA, Health Care Financing Administration; RDD, random digit dialing.


    INTRODUCTION
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
The National Institutes of Health 1993 Revitalization Act (1) mandates inclusion of minority groups in clinical research to address their historical underrepresentation. In case-control studies that use population-based cancer registries to access cases, population-based recruitment of controls is the standard methodology in order to sample from the same source population. Yet, little evidence exists to assess the effectiveness of population-based recruitment methods for studies involving ethnically diverse groups (2).

Lung cancer is the leading cause of cancer mortality in the United States for both men and women (3). This paper reports strategies used to recruit African Americans, who on average bear a disproportionate burden of lung cancer, and Latinos, who have relatively lower rates of the disease. For example, in the San Francisco Bay Area of California from 1995 to 1999, the age-adjusted lung cancer incidence rates per 100,000 population were 65 for White, non-Hispanics; 80 for African Americans; and 36 for Hispanics (4). Ethnic differences in lung cancer incidence and survival have yet to be adequately explained and probably reflect environmental, lifestyle, biologic, and genetic influences. Comparing the effects of these factors in a very low-risk and a very high-risk population may help clarify how these factors interact to influence lung cancer risk. Elucidating the interplay of these factors is crucial to developing intervention and prevention strategies.

Both Latinos and African Americans have traditionally been underrepresented in health research. Therefore, there are limited data on the effectiveness of various recruitment strategies in these groups (513) and questionable generalizability of risk factors for lung cancer observed in previous case-control studies conducted in primarily White populations. In a previous lung cancer susceptibility study, which included African Americans and Caucasians in Los Angeles, California, controls were recruited through a combination of Department of Motor Vehicle records and Health Care Financing Administration (HCFA) listings (5); the investigators enrolled about 22 percent of the original group of potential controls identified or 26 percent of those not determined to be ineligible. They did not break down the results of control recruitment by ethnic group. More information is needed on the challenges and successes associated with the use of various recruitment methods in ethnically diverse populations.

The main purpose of this case-control study (1998–2001) was to examine genetic, behavioral, and occupational factors of potential etiologic significance in the occurrence of lung cancer among San Francisco Bay Area African Americans and Latinos. In this interim report, we briefly report on recruitment results for the lung cancer cases, but our emphasis is on comparing population- and community-based methods of recruiting controls. We compare 1) the effectiveness, by ethnic group, of the recruitment methods used; and 2) control groups on demographic characteristics and lung cancer risk factors across method of recruitment and with lung cancer cases to evaluate potential bias introduced by recruitment method.


    MATERIALS AND METHODS
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Recruitment of controls
We used three recruitment strategies to enroll controls. Controls from the same geographic area were frequency matched on age and gender to lung cancer cases (with a ratio of 2:1) and were ascertained by using both population-based sampling and community-based recruitment methods.

Our initial approach was to use random digit dialing (RDD); telephone interviewers were fluent in both Spanish and English. However, because of the limited number of potentially eligible elderly African-American and Latino subjects identified through RDD, we turned to HCFA beneficiary records to identify controls aged 65 years or older. When these two population-based methods failed to yield sufficient numbers of eligible controls, we began community-based recruitment methods targeting churches, health fairs, senior centers, university employees, and patients of primary care physicians serving African Americans and Latinos.

To obtain eligible controls through RDD (13), we generated numbers based on 1997 listings for lung cancer cases provided by the Northern California Cancer Center for the five Bay Area counties (Alameda, San Francisco, Contra Costa, San Mateo, and Santa Clara). To generate these numbers, we used the telephone numbers (area code and first five digits) of the case listing, then we randomized the last two digits to achieve telephone numbers matching on county of residence. We also purchased from a vendor listed population-based samples, matching on age, ethnicity, gender, and county of residence. Telephone calls were made to enumerate the households; to ascertain the age, gender, and ethnicity of residents; and to obtain names and mailing addresses.

HCFA provided the name, address, age, gender, and ethnicity, but not the telephone number, of African-American and Latino beneficiaries living in the five Bay Area counties. We randomly selected 400 eligible participants and sent them letters on HCFA stationery introducing the study. A letter from the study team followed, explaining the nature of the study and requesting, on a reply/refusal postcard, a telephone contact number. For potential participants who did not decline via postcard, we conducted computer searches for telephone numbers and conducted home visits when searches for telephone numbers were not successful.

We developed community-based recruitment strategies targeting faith-based institutions (churches), health fair attendees, senior centers (housing and community centers), university employees, and physicians serving African Americans and Latinos. Working through established community linkages, an ethnically diverse staff of interviewers and outreach workers provided group and individual-level presentations and disseminated informational flyers and study brochures at church seminars, health fairs, and senior centers. Patients identified by their physician were sent letters of information about the study, and recruitment letters were sent via campus mail to African-American and Latino university employees.

Recruitment of lung cancer cases
Cases were ascertained from those reported to the Northern California Cancer Center, a population-based Surveillance, Epidemiology, and End Results cancer registry. Rapid case ascertainment methods, which consist of on-site medical record abstraction by trained registry staff, were used to maximize the chances of contacting cases prior to death. Although Surveillance, Epidemiology, and End Results files include ethnicity, rapid case ascertainment does not, and telephone screening was necessary to identify the ethnicity of cases. Eligibility criteria for lung cancer cases included 1) self-identified Latino or African-American ethnicity; 2) residence in Alameda, San Francisco, Contra Costa, Santa Clara, or San Mateo counties; 3) age of 21 years or older; and 4) a presumptive diagnosis of primary lung cancer. Decedents were not eligible for study participation, and proxy interviews were not conducted. Interview information and biologic samples (buccal smears and blood samples) were collected at a site selected by the participant, generally the residence.

For lung cancer cases, a letter was sent to the physician of record advising that the patient would be contacted to participate in the study and asking the physician to contact the researchers if there were any contraindications to the patient’s participation. If no response was received from the physician, the patient was sent a letter from the research team with a return acceptance/refusal postcard. Patients who did not refuse via postcard were then contacted by telephone by a language-matched interviewer to determine their ethnicity and assess their interest in participating in the study.

Tracking procedures
A computerized tracking system was used to examine the disposition of each potential case and control by ethnicity and method of recruitment. To assess the effectiveness of the various methods used to recruit controls from each ethnic group, we tracked the number in the original sampling frame (where available), the number successfully contacted, the number completing an eligibility interview, the number eligible for the study, and the number completing the full interview (including biologic samples). For controls, we also maintained a log of recruiting hours spent by recruitment method. We divided the total number of hours spent for each method by the number of controls resulting from that method to calculate the average number of interviewer hours per control interviewed for each recruitment method.

Data analysis
We compared characteristics of interviewed controls by method of recruitment to determine differences and similarities with respect to demographic and socioeconomic factors, smoking history, and smoking pack-years (1 pack-year = smoking the equivalent of one pack of cigarettes per day per year; e.g., 40 pack-years could be one pack a day for 40 years or two packs a day for 20 years) as well as occupational asbestos exposure history related to lung cancer risk. For Latinos, we also compared birthplace and English language fluency. In addition, we compared controls with cases regarding the same characteristics. Analyses were stratified by ethnicity. Analysis of variance was used to assess differences in continuous variables, and logistic regression was used to compare binary variables after adjusting for age and gender effects (except for age and gender comparisons).


    RESULTS
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Recruitment of controls
Table 1 summarizes recruitment of controls by ethnicity and method. Overall, approximately 4 percent (244/6,376) of RDD numbers dialed yielded potentially eligible controls; 62.3 percent (152/244) of those eligible participated. One fourth (1,627/6376) of the telephone numbers used in RDD were ineligible because of the respondent’s ethnicity, 18.3 percent (1,165/6,376) of the numbers had been disconnected, and 11.7 percent were for persons who were ineligible because of their age (748/6,370). Almost all (94.5 percent; 378/400) potential controls identified through HCFA records were eligible. However, only 21.4 percent (81/378) of persons eligible for the study were recruited. There is no comparable denominator of the number of persons contacted for community-based outreach methods since these persons did not constitute a defined population. Of those accessed through community channels and identified as eligible for the study, 81.2 percent participated. The yield of eligible controls identified and eligible controls recruited by each of the recruitment methods was similar by ethnic group. African-American controls represented 66 percent (385/582) and Latinos 34 percent (197/582) of the total controls participating, reflecting the proportion of enrolled African Americans and Latinos with lung cancer.


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TABLE 1. Recruitment of controls, by ethnicity and method, San Francisco Bay Area Lung Cancer Study, California, 1998–2001
 
Characteristics of controls by recruitment method
African-American controls recruited by RDD and community-based methods were similar with respect to age and gender, but HCFA controls were significantly older (p < 0.001), as expected (table 2). Regarding sociodemographic characteristics by method of recruitment, African-American RDD controls tended to report a higher average household income. This difference in income was statistically significant for African-American RDD controls compared with African-American community-based controls (p < 0.005). Although African-American HCFA controls reported a higher number of pack-years than those recruited by RDD or community-based methods, these differences were not statistically significant. After adjustment for differences in age, cumulative smoking exposure in pack-years was greater among African-American community-based controls compared with RDD controls (p < 0.005).


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TABLE 2. Characteristics* of African-American controls who completed the full questionnaire and provided a biologic sample, by recruitment method, San Francisco Bay Area Lung Cancer Study, California, 1998–2001
 
Among Latinos, HCFA controls tended to be older (p = 0.0001) and included more men compared with RDD (p < 0.05) or community-based controls (p = 0.0001) (table 3). Compared with controls recruited by using HCFA or RDD methods, a smaller proportion of Latino community-based controls were born in the United States (p < 0.05). Latino controls recruited through community channels had the highest average number of years of schooling and included the highest percentage of high school graduates (table 3). These differences were significant for years of schooling comparing RDD and community-based controls (p < 0.001) and for the proportion of high school graduates comparing either RDD or HCFA with community-based controls (p < 0.05). The controls did not differ with respect to average household income. Latino RDD controls reported a significantly higher number of smoking pack-years than HCFA controls but not community-based controls did (p < 0.05) (table 3) after we adjusted for differences in age.


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TABLE 3. Characteristics* of Latino controls who completed the full questionnaire and provided a biologic sample, by recruitment method, San Francisco Bay Area Lung Cancer Study, California, 1998–2001
 
Intensity of recruitment effort by method
The RDD method was the most labor intensive of the three recruitment methods, requiring 18.6 hours on average to recruit a control compared with 11.4 hours for each HCFA control recruited. As expected, community-based methods required much less effort in terms of both time and labor. On average, community-based methods that we used required less than an hour (40 minutes) per eligible control recruited. Of the four methods used, mailings to patients and university employees were the most efficient; about 10 minutes per recruited control was required. Recruitment at health fairs was the least productive of the community-based methods: 1.6 hours per eligible control. Presentations at faith-based institutions and senior centers averaged 15 minutes per recruited control. These numbers apply to efforts to identify eligible controls only, not to the time spent arranging and conducting interviews.

Recruitment of lung cancer cases
Of the initial 5,329 primary lung cancer cases identified through rapid case ascertainment, 732 were determined eligible by race/ethnicity; 470 were African American and 262 were Latino. These figures represent study ascertainment of eligible Latino and African-American cases during the period September 1, 1998–July 11, 2001. Of persons with lung cancer reported by the registry, 53.4 percent self-identified as being in other ethnic groups, mainly White, non-Latino. We were unable to establish the ethnicity of almost one third of the reported cases because of incorrect contact information, inability to reach potential respondents, or refusal by potential respondents or their physicians (table 4).


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TABLE 4. Ascertainment of the ethnicity of tumor registry lung cancer cases by using telephone screening, San Francisco Bay Area Lung Cancer Study, California, 1998–2001*
 
Despite the use of rapid case ascertainment methods, 38.5 percent of African Americans and 43.1 percent of Latinos were deceased when the initial contact was attempted (table 5). The median time elapsed between date of diagnosis of lung cancer and date of initial contact letter was 56 days for African Americans and 62 days for Latinos. The proportion of lung cancer cases deceased when the initial contact was attempted was substantially higher for African Americans (38.5 percent) and Latinos (43.1 percent) than for those from other ethnic groups (21.8 percent) or those whose ethnicity was unknown (26.7 percent). About 4 percent of African-American and 4 percent of Latino cases were unable to participate because of poor health. Refusal rates for potentially eligible participants who were contacted successfully were low for both African-American (7.9 percent) and Latino (8.8 percent) lung cancer cases. Not including those who were deceased or whose physicians refused to allow them to take part, full participation rates (completed full questionnaire and provided biologic sample) were 72 percent among African Americans (207/288) and 68 percent among Latinos (101/149) (table 5). An additional 5 percent of African Americans and 7 percent of Latinos agreed to complete a brief screening questionnaire, resulting in participation rates for the screener or full questionnaire plus biologic sample of 77 percent for African Americans and 76 percent for Latinos.


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TABLE 5. Disposition of tumor registry lung cancer cases, by ethnicity, San Francisco Bay Area Lung Cancer Study, California, 1998–2001
 
Comparison of cases and controls
Despite frequency matching, African-American controls were significantly younger than African-American cases (p < 0.05) because this is an interim analysis. All comparisons were adjusted for age and gender. Among African Americans, cases also appeared to be disadvantaged relative to controls in terms of socioeconomic indicators, such as years of schooling (p < 0.001) and percentage of high school graduates (p < 0.05) (table 6). As expected, African-American cases reported higher levels of smoking-related risk factors, such as ever smoking (p < 0.0001), number of pack-years (p < 0.0001), and number of years of smoking (p < 0.0001), and a higher proportion had a history of occupational exposure to asbestos compared with controls (26 percent vs. 13 percent, p < 0.001).


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TABLE 6. Comparison of the characteristics* of African-American and Latino controls and cases who completed the full questionnaire and provided a biologic sample, San Francisco Bay Area Lung Cancer Study, California, 1998–2001
 
Latino cases also were significantly older (p < 0.05) than Latino controls in this interim analysis (table 6). Latino cases reported fewer years of schooling (p < 0.05) and included a lower proportion of high school graduates (p < 0.05), but they were not significantly different from controls regarding average household income. Latino cases reported significantly higher levels of smoking-related behaviors than Latino controls for such indicators as ever smoked (p < 0.0001), number of pack-years (p < 0.0001), and number of years of smoking (p < 0.0001). No differences were found between Latino controls and cases regarding percentage with occupational asbestos exposure (p = 0.2460).


    DISCUSSION
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Minority participation in biomedical and epidemiologic research is limited, and empirical data on the experiences and outcomes of recruiting African-American and Latino research participants are lacking. We collected data on the recruitment efforts in a case-control study of lung cancer susceptibility in African Americans and Latinos.

We were unable to meet control recruitment goals in a timely and cost-effective manner by using standard population-based methods. This problem was due to the age and ethnic distribution of eligible controls in the population. RDD required a tremendous amount of effort for a low yield of eligibles identified. However, a majority of eligible persons identified agreed to participate (62.3 percent). The HCFA method, on the other hand, was an excellent way to identify people who were eligible, but it was only marginally successful as a means of enrolling participants (21.4 percent). These results were expected given that information on ethnicity was not available for RDD until potential participants were screened; for HCFA, ethnicity but no telephone numbers were included in beneficiary records.

Community-based methods were much more effective than RDD and HCFA methods in enrolling eligible Latinos and African Americans since we were able to select sites with high concentrations of our targeted populations. Nevertheless, much work is still needed in future studies to determine optimal and valid recruitment methods for minorities.

After we adjusted for age, African-American controls recruited by using HCFA methods tended to be heavier smokers and longer-term smokers than those recruited through the other two methods. African-American community-based controls may be more representative of the general San Francisco Bay Area African-American population; HCFA beneficiaries represent only those aged 65 years or older, and RDD controls were persons who could be contacted by telephone. African-American cases appeared to be less educated than African-American controls and had higher numbers of smoking and occupational risk factors for lung cancer, as would be expected.

Latino community-based controls were less likely to be US born but tended to be better educated than RDD and HCFA controls. Despite these sociodemographic differences between Latino controls and cases, they were similar in terms of occupational factors that are putative lung cancer risk factors but demonstrated expected differences in tobacco-related risk factors. Latino cases tended to be older, which might explain why they tended to be less educated relative to Latino controls; that is, there may have been some residual confounding with age. Similar to the African Americans, Latino cases demonstrated a higher level of smoking-related risk factors than controls did, although they did not differ regarding occupational factors.

Studies suggest that people of lower socioeconomic status and those from minority groups may be less likely to respond to traditional recruitment efforts than those of higher socioeconomic status or nonminorities and are underrepresented in health research (8). There is some evidence pertaining to factors associated with the lower participation rates of diverse ethnic groups but little evidence about the effectiveness of specific recruitment methods. Barriers to recruitment and lack of study response may be attributable to a number of factors, including negative attitudes and beliefs about research, mistrust of researchers, lack of culturally and linguistically competent staff and recruitment processes, and limited representation of minority health researchers (912). These results demonstrate differences in success rates in the recruitment of controls comparing two population-based methods (RDD and HCFA) with community-based, nonprobabilistic, and non-population-based sampling methods. Community-based strategies involving initial contact by in-person presentations and/or face-to-face discussions were more effective than traditional population-based recruitment methods, which involved initial contact by telephone. Through face-to-face contact, study outreach staff may have overcome some of the barriers to recruitment, as evidenced by the higher yield of controls recruited by using community-based methods.

Although use of probabilistic methods is intended to help guard against sampling bias, the lower percentages of eligible participants recruited by using specific population-based methods (62 percent for RDD and 21 percent for HCFA) calls into question the representativeness of controls obtained by using these methods. Therefore, we resorted to community-based methods, which also have a potential for sampling bias.

Screening of potential cases provided by the tumor registry for eligibility regarding ethnicity required a large effort since less than 14 percent of the sampling frame was eligible for the study. Additionally, lung cancer mortality made recruitment especially challenging among Latinos and African Americans; approximately 40 percent were deceased when we attempted to contact them, even though rapid case ascertainment was used. However, of those living cases with whom we established contact, participation rates were fairly good (68 percent for Latinos and 72 percent for African Americans), and participant refusal rates were relatively low (8 percent for African Americans and 9 percent for Latinos).

It would be valuable to know what biases were introduced by the use of community-based methods. Our study may be limited because we used nonrandom methods to select controls and because of biases potentially introduced by using these methods. When we compared selected characteristics of our population of controls with those of the population of our targeted five-county area, we learned that educational status and average household size were comparable. However, study controls tended to have a lower median household income and were less likely to be single. US Census data for our five-county area were readily available only on income for persons aged 15 years or older and on education for those aged 25 years or older. Thus, differences between study controls and the US Census data for the five counties might be explained partially by the older age distribution of our control population because of matching to cases on age (14). In future studies that involve resorting to non-population-based methods to recruit controls, investigators will need to exercise caution and collect data that may facilitate assessment of selection bias and potential confounding introduced by such nonrandom sampling methods.

Our results highlight the effectiveness of using alternative methods to recruit African-American and Latino participants into a case-control study of lung cancer susceptibility. Our willingness to try alternative recruitment strategies resulted in greater research participation. When traditional population-based methods failed to yield adequate numbers of controls, we explored the use of community-based recruitment methods to locate subjects who historically have been difficult to recruit. By using the talents of a diverse team and established community linkages, we identified and tapped into an eligible subject pool and successfully met recruitment goals for controls matched to cases on age, ethnicity, gender, and county of residence.


    ACKNOWLEDGMENTS
 
This research was supported by grant ES06717 from the National Institute of Environmental Health Sciences (NIEHS). The work of Drs. Nápoles-Springer and Pérez-Stable was also supported by the Resource Center for Minority Aging Research program of the National Institute on Aging, the National Institute of Nursing Research, and the Office of Research on Minority Health, grant P30 AG15272.

The authors are indebted to the study interviewers and outreach staff, Starr Amrit, Lizette Alvarez, Dr. Maria Diaz, Latonya Goodson, Doris de Leon, Dr. Wendy Lorizio, Dr. Julie Madsen, Nkem Ogbechie, Csaba Polony, Natalia Ramirez, James Taylor, and Jaime Wong-Dominguez.


    NOTES
 
Reprint requests to Dr. Daramöla N. Cabral, Northern California Cancer Center, 32960 Alvarado-Niles Road, Suite 600, Union City, CA 94587 (e-mail: dcabral{at}nccc.org). Back


    REFERENCES
 TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

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