Affiliations of authors: D. B. Buller, AMC Cancer Research Center, Denver, CO; C. Morrill (Department of Sociology), D. Taren (Nutrition and Physical Acitivity Unit, Arizona Prevention Center), L. Sennott-Miller (College of Nursing), T. M. Wentzel (Arizona Cancer Center), University of Arizona, Tucson; M. Aickin, Center for Health Research, Kaiser Permanente Northwest Division, Portland, OR; M. K. Buller, Department of Technology Transfer, Partners for Health Systems, Inc., Denver; L. Larkey, Women's Cancer Prevention Research Initiative, Arizona Cancer Center, University of Arizona; Phoenix; C. Alatorre, Statistical and Mathematical Sciences, Lilly Research Laboratories, Eli Lilly & Co., Indianapolis, IN.
Correspondence to: David B. Buller, Ph.D., AMC Cancer Research Center, 1600 Pierce St., Denver, CO 80214 (e-mail: bullerd{at}amc.org).
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ABSTRACT |
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INTRODUCTION |
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Peer health education is commonly used to communicate health information to underserved populations (9,10). Peer health educators are effective because they alter the normative and communication environment in informal social groups (11,12). Members of social groups demonstrate their commitment to the group (13-15) and maintain the group's identity (16) by conforming to the new health norms advocated by peer educators. Peer educators also marshal social support that helps others to overcome barriers to healthy behavior and reinforces decisions to adopt the healthy behavior. Other adults also may reciprocate peer educators' expression of support by adopting their recommendations for healthy behavior (17). Finally, peer educators serve as informal opinion leaders who improve the quantity of messages about healthy behavior (18), tailor messages to the unique needs and culture of a social group (11,19,20), and stimulate a classic diffusion of innovation process (18). The group processes promoted by peer education can produce changes that are longer lived than changes created by individual decision processes because the group's social support and norms are more resistant to change than the individual's beliefs and attitudes (14,15,21).
Our intervention method by peer education was evaluated on a lower income, multicultural population in the southwestern United States, a population that often has less information about cancer and nutrition (22-25). Many people in this population hold labor and trades, blue-collar occupations (53% of Hispanics in U.S. work force; 52% of Hispanics in Arizona work force), particularly the men (64% of Hispanic males in U.S. work force; 62% of Hispanic males in Arizona work force) (26). Informal social networks at work provide important information and social support for employees (27-30), and community-based peer educators have delivered advice to people while at work (11). Work site peer education should overcome barriers to wellness activities for these employees, such as shorter break times, less flexible hours, offsite and multiple work areas, and uneven English usage.
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SUBJECTS AND METHODS |
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Employee Population and Baseline Sample
Labor and trades blue-collar employees from 10 public employers (two county governments, two city governments, two public universities, two community colleges, and two public school districts) in Tucson and Phoenix, AZ, were recruited to the study from facilities management, automotive and fleet services, communications, water services, food services, housekeeping/laundry, groundskeeping, parks and recreation, custodial services, solid waste, and streets and transportation departments. Recruitment occurred by formal work group to obtain collections of employees who had regular informal contact on a weekly basis with one another. Senior managers identified work groups and secured access to them. Supervisors were ineligible to participate so that we could control for the effects of formal authority among participants.
One hundred twenty-six work groups containing 2530 eligible employees agreed to
participate in a baseline survey that was completed with 2091 employees (83%). See Fig. 1 for trial flow chart. The university's institutional review
board approved all trial procedures and classified the project procedures as exempt. Interviewers
read a written consent statement to all employees, and employees' consent to participate
was obtained before the baseline interview was conducted. The majority of the employees
completing the baseline survey were male, married, moderately educated, and middle-aged. The
size of their families was slightly larger than the national average, and they had low to middle
household incomes (many with multiple income earners). Tobacco use was slightly higher than the
national adult average. The employees exhibited a range of ethnic identifications; most were white
or Hispanic. Almost all Hispanic employees were born in the United States, had limited contact
with Mexico, and identified somewhat with the Anglo culture, yet they reported a great degree of
ethnic pride. Employees spent a large amount of work time off-site; some of these employees
worked fewer than 40 hours and, in total, averaged nearly 10 years at their current job (Table 1
).
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The peer education program was tested with a randomized design with the use of
preintervention and postintervention measures of fruit and vegetable intake and related beliefs and
attitudes (Fig. 1). Employee recruitment and the baseline survey were
performed from May 1993 to February 1994.
General Five a Day Program. Beginning in 1995, an 18-month General Five a Day Program was delivered to all employees at each work site regardless of job type through formal work site communication channels (mail, posters, cafeteria promotion, and guest speakers). Research staff supplied managers (e.g., communications, wellness, and cafeteria) with printed program materials from the National Cancer Institute's Five a Day for Better Health Program; managers distributed the materials through company mail and posted them in workplaces and cafeterias; and research staff visited work sites to measure program implementation and to solve problems. Process measures confirmed that nearly 200 000 intervention items were used.1 Guest speakers were identified by research staff who assisted managers with scheduling and conducting speaker sessions at the work sites. Program themes across the 18-month General Five a Day Program were rotated in 6-month intervals; program activities occurred every other month.
This program provided a baseline awareness level of the National Cancer Institute's Five a Day for Better Health Program that was equalized in intervention and control work groups prior to launching the peer education program. It provided a non-peer-based intervention to the control groups to eliminate the potential of a Hawthorne effect (i.e., changes observed in response to peer education are not due simply to being treated but rather to the nature of the intervention). It also increased employer and employee participation by ensuring that all employees received some nutrition education.
Identifying, matching, and randomizing informal social networks. The unit of
matching and randomization was the informal social network of employees, specifically cliques.
Cliques are informal networks in which members interact more with each other than surrounding
people within their work groups (33). The request for applications from
the National Cancer Institute under which this project was funded required that applicants project
sample size based on an increase of 0.50 daily servings of fruits and vegetables, which the
National Cancer Institute's staff had selected as a meaningful level of dietary change. To
detect this level of dietary change, we determined that 40 matched pairs of informal social
networks were required to achieve statistical power at 0.80, with an alpha () criterion of
0.05 (two-tailed).
Network data were collected via a sociometric question in which respondents were asked to name up to eight co-workers in their work group with whom they talked. Respondents were then asked to rate each named person on five social-tie dimensions (using 5-point scales): 1) contact frequency (never, rarely [once or twice a year], sometimes [once or twice a month], often [once or twice a week], or very often [once or twice a day]), 2) personal relationship (acquaintance, friend, good friend, close friend, or very close friend), 3) frequency of health- and diet-related conversations (never, rarely, sometimes, often, or very often), 4) respect for co-worker's opinions about health-related information (very little, little, some, much, or very much), and 5) frequency of eating lunch together (never, rarely, sometimes, often, or very often).
Multistage social network analysis detected 93 cliques in person-to-person data matrices on
contact frequency, with the use of sorting algorithms in UCINET software (34) (Fig. 1). A clique was formally defined as an informal
referent group in which co-workers were no more than two social-tie lengths (e.g., friends of
friends) away from one another. (Cliques defined by direct ties only yielded groups that were too
small.) When multiple overlapping cliques existed, the clique with the most members was
selected; if multiple "largest" cliques of the same size were detected, the clique
with the highest density was selected. Density is a measure of strength of social ties in a group,
operationalized for the purposes of this study as the mean rating for each social-tie dimension
within each clique (35). At baseline, the median clique size was 11 (range
= 5-18; 25th-75th percentile = 10-13).
The cliques were pair matched on the basis of the clique-level average total daily consumption (servings) of fruits and vegetables, stage of readiness to increase fruit and vegetable consumption, clique density, co-worker and management support for health, perceived self-efficacy for increasing fruit and vegetable consumption, proportion of Hispanic employees, proportion of female employees, and clique size from the baseline survey. One clique within each pair was randomly assigned to the intervention group receiving the Five a Day Peer Education Program plus the General Five a Day Program, and the other was randomly assigned to the control group receiving only the General Five a Day Program. Matching and randomization were performed by the project biostatistician, who had no contact with peer educators.
After initial randomization, pairs were inspected for physical proximity to each other. Randomization within seven pairs where cliques were in close physical proximity was adjusted to eliminate diffusion of peer education into the control group. At the end of the study, only five employees had moved from one clique to another (one by interim survey, two by outcome survey, and two by follow-up survey). In self-report measures of contact with co-workers, only seven employees at the outcome survey and 10 employees at the 6-month follow-up reported talking with employees from another clique. The average proportion of cross-clique contacts per clique reported by employees at the outcome survey was 0.006 and 0.007 at follow-up. Thus, there was almost no opportunity for diffusion. In the analysis, these employees were retained as members of their original baseline cliques.
Rematching at interim survey. During months 8 and 9 of the General Five a Day
Program, work groups were recontacted (following matching and randomization), and an interim
survey was performed with employees in the cliques. Eleven cliques were removed from the trial
that no longer existed, whose employees refused to participate further, or in which no employee
would serve as a peer educator. As a result, six cliques were re-matched and re-randomized. In
addition, 140 employees were removed from the trial prior to the interim survey because they no
longer were members of the cliques. Also, four did not complete the interim survey but returned
to the study at the outcome or follow-up surveys. Thus, at the interim survey and just prior to the
beginning of the Five a Day Peer Education Program, 41 cliques with 395 employees were
assigned to receive this intervention, 41 cliques with 371 employees were assigned to serve as
controls (Fig. 1), and one extra clique remained unmatched and was not
randomized. Employees' membership in their clique and clique assignment to study
condition were fixed at the interim survey, and attempts were made to complete the outcome and
follow-up surveys with all clique members, even those who left the clique and/or employer.
Five a Day Peer Education Program. This program was implemented during the last
9 months of the General Five a Day Program. Three months before implementation, an employee
in each intervention clique was recruited to be a peer educator. These employees were highly
central within the clique in terms of communication ties and flow. As such, they were skilled at
communication, had strong relationships with their co-workers, were capable of accessing all
co-workers, and could be opinion leaders in the group. Centrality was measured with the use of a
"peer index" at baseline, calculated as a combination of "betweenness
centrality," i.e., the ability to intercept or to modify information in a clique assessed as the
probability that any one individual is connected to two other members who are not directly
connected (36); "degree centrality," i.e., social prominence
or status indicated by the number of times a person was named by other clique members (36); and "average strength of tie," i.e., the mean rating on
each social tie context received by each person. The peer index was the grand mean of the rank of
each clique member on these measures relative to other clique members. Researchers first
contacted the employee with the highest peer index for recruitment. If that employee declined, the
one with the second highest peer index was recruited and so on. The majority of the peer
educators had either the highest (38% in Tucson and 21% in Phoenix) or the second
highest (56% in Tucson and 37% in Phoenix) peer indices. Employees were
ineligible to be peer educators if their supervisor objected to them serving as one or they planned
to take a leave of absence or retire before the final survey. Peer educators shared many of the
demographic characteristics with the study cohort, although their education and age ranges were
more restricted and there were more Hispanics than in the study cohort (Table 1).
Peer educators attended a 16-hour training program conducted by the researchers over an 8-week period. This training program used presentations, group discussions, and role playing to cover a range of topics: (a) the health benefits of eating fruits and vegetables; (b) cultural trends in dietary practices; (c) methods of incorporating the topic of fruits and vegetables in informal communication at work, gaining compliance, and motivating behavior change; and (d) peer educators' role and responsibilities as peer educators in the study. Peer educators were told that the project expected them to spend about 2 hours per week discussing eating fruits and vegetables with co-workers. Peer educators were taught five persuasive communication strategies (foot-in-the-door, fear appeal, benefits, peer pressure, and questioning) and ways to initiate informal conversations about fruits and vegetables (e.g., noticing what a co-worker brought for lunch; using a media story as a segue into a Five a Day conversation; and hosting contests, potluck meals, and group discussions) in one-on-one interactions, small group discussions, or presentations at safety or staff meetings. Peer educators were not involved in the implementation of the General Five a Day Program described earlier. While peer educators' focus was to be on co-workers in their cliques, they were not discouraged from talking with employees outside them.
Peer educators (a) kept records of contacts with co-workers, (b) attended monthly 2-hour in-service training session with researchers to review activities, solve problems, and discuss special topics, and (c) spoke by telephone monthly with researchers about their progress. Logs of contacts with co-workers kept by peer educators and questions posed to co-workers at the outcome and follow-up surveys confirmed that they regularly discussed eating fruits and vegetables with co-workers and attempted to influence them to eat more of these foods (32).1 For example, peer educators recorded more than 9000 contacts with co-workers, and 95% of employees surveyed in intervention cliques reported having a discussion about fruits and vegetables and receiving printed Five a Day materials from the peer educators.
Printed Five a Day materials were prepared by the researchers to be used by peer educators with their co-workers. The Five a Day Guidebook contained nine themed booklets, collected in a three-ring binder for storage, which peer educators distributed one a month. They contained culturally and regionally appropriate nutrition information (e.g., recipes and foods used in the Anglo and Mexican diets in Arizona, monthly listing of in-season Arizona-grown fruits and vegetables, Spanish translations and summaries, Mexican holidays and events, and Mexican-American and Anglo characters) to influence knowledge, attitudes, stages of change, skills, and barriers (e.g., general availability, cost, time, and satisfaction with taste) for eating fruits and vegetables. Features included articles and reports, a question-and-answer column, photonovella (continuing melodrama in photographs like a comic strip about a peer educator, co-workers, and family members), low-literacy graphics and stories, calendar of seasonal fruits and vegetables, activities for children, recipes and regional foods, and tips and facts. Four issues of The Five a Day Way newsletter directed employees to program events at their work sites and were distributed by peer educators every other month. Peer educators also provided one item each month (e.g., water bottle, recipe books, sample produce, and vegetable seeds) to help co-workers practice dietary skills, but these items were not used as incentives for any action. Peer educators distributed printed materials as intended, and employees read and often discussed these materials with co-workers and family members.1
Peer educators were paid $1800 for time spent in training, traveling to training, distributing materials, talking with co-workers for about 2 hours per week, and keeping daily logs of their contacts (approximately 165 hours). It is a common practice to pay lay advisors (20). Two peer educators were lost during the intervention; one was reassigned to another work group, and the other quit being a peer educator. Two replacement peer educators with high centrality scores were trained to continue the intervention with minimal disruption.
Outcome and Follow-up Surveys and Measures
An outcome survey was performed with employees in the cliques at the conclusion of
intervention activities, and a follow-up survey was conducted 6 months afterwards by trained
interviewers, some of whom were bilingual (English and Spanish). Interviews were conducted
with employees individually, face-to-face, and during work time at the work site, with the
approval of the employers (Fig. 1). We were unable to locate and
interview 36 employees at the outcome survey and another 35 employees at the follow-up survey
who had left the employer, so they were removed from the analysis. Thus, 41 cliques with 363
employees completed the trial in the intervention group and 41 cliques with 332 employees
completed the trial in the control group (Fig. 1
).
Survey questions assessed job and sociodemographic characteristics, co-worker and management support for healthy behaviors, sources of health information (37), self-efficacy expectations, attitudes toward cancer prevention, personal and family histories of cancer (38), and acculturation. Interviewers were unaware of the assignment of a clique to intervention or control condition. Measures of and evaluation of peer educator activities were asked at the end of the surveys, after all outcome measures had been obtained.
Measures used in the analyses reported here included an item measuring awareness of the Five a Day Program (i.e., Had employees heard of the Five a Day for Better Health Program?"yes" or "no") and an item assessing knowledge of the recommendation to eat five servings of fruits and vegetables daily (24). Attitudes toward fruit and vegetable consumption written for this study were measured with the use of 5-point Likert-type agree/disagree items. The primary measure of daily fruits and vegetables intake was a 24-hour intake recall on which interviewers recorded each food item eaten (as reported by an employee), the portion size, and the number of times each food item was eaten during the previous 24 hours (39). When probing for portion size, interviewers used 8- and 16-ounce glasses and half- and one-cup bowls. Research staff converted the interviewers' reports to servings of fruits and vegetables. Measures were created of the number of servings of fruits, vegetables, fruit juices, and in total consumed during the last 24 hours, excluding olives, avocados, coconut, fried potatoes, French fries, and cranberry juice (which is not 100% fruit juice) per the National Cancer Institute's guidelines. Seven food-frequency questions assessed consumption of 100% orange or grapefruit juice, other 100% fruit juices, green salad (with or without other vegetables), French fries or fried potatoes, other potatoes (e.g., baked, boiled, and mashed), vegetables not counting potatoes and green salads, and fruit not counting fruit juices, which provided a secondary measure of daily intake over a typical month (8).
Statistical Analysis
The analysis was based on clique-level averages of the outcome measures, since clique was
the unit of randomization. Pairing of cliques was also included in the design of the analysis based
on clique-level average total daily consumption (servings) of fruits and vegetables, stage of
readiness to increase fruit and vegetable consumption, clique density, co-worker and management
support for health, perceived self-efficacy for increasing fruit and vegetable consumption,
proportion of Hispanic employees, proportion of female employees, and clique size from the
baseline survey. All outcomes were analyzed with the use of the following method: First, the
difference in outcome between baseline and outcome surveys was computed for each intervention
clique, d1, and each control clique, d0. Second, the
difference between these changes, dd = d1 - d0,was computed within each matched pair of cliques, yielding 41 outcome values.
Finally, the analytic model was simple linear regression, dd = + ßd0 + e, where e is assumed to have a mean of zero
and be independent of d0, and d0 is centered at its mean.
Including the d0 term is a way of controlling for the regression to the mean
phenomenon; in fact, this analysis is a variant of the conditional change model (40) that is widely recommended for studies of change. The parameter measuring effect
is
, which would be zero if the only effect on difference between change (dd) were
regression to the mean (ß). The customary .05 (two-sided) criterion was used for assessing
statistical significance. This analysis procedure was planned in the original study protocol and was
the basis for the sample size determination.
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RESULTS |
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Compared with those not in eligible cliques, employees in the 93 eligible cliques at baseline (a) were less likely to agree that what they eat or drink is one of the most important things that affects how healthy they are (two-tailed P = .004); (b) ate fewer total daily servings of vegetables, not counting potatoes and green salads (P = .001); (c) received more health information from people with whom they work (P = .012); (d) were more likely to agree that drinking alcohol does not increase their risk of getting cancer (P = .016); (e) had spent more years at their job (P = .002); (f) had higher annual household incomes (P<.0001); and (g) had less contact with Mexico (P = .014). In addition, compared with those not in eligible cliques, more of the employees in the eligible cliques (h) were born in the United States (P = .001); (i) had a high school education or a trade, technical, or vocational education (P = .010); and (j) were male (P = .018). No general selection bias was evident: Having more information from people at work and being more acculturated and affluent might facilitate the peer education intervention, but believing that diet is less important for good health, believing that alcohol and cancer are related, having lower baseline fruit and vegetable intake, and being male may impede its success.
Immediate Changes in Awareness, Attitudes, and Dietary Behavior
The intervention and control cliques were at substantially the same
levels of all of the outcome measures at baseline (Table
2). The largest statistically significant
differences were that employees in the intervention cliques thought
that an appropriate number of daily servings of fruits and vegetables
was about 0.20 lower than did the control cliques. Also, according to
both the intake recalls and food-frequency questionnaire, the reported
total daily servings were lower among the intervention than the control
cliques (by 0.23 and 0.20 servings, respectively).
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Overall, 11 of the 15 outcome measures showed statistically significant intervention effects in the expected direction of increase in intake.
Persistence of Changes in Awareness, Attitudes, and Dietary Behavior
The 6-month follow-up study showed a general persistence of the
intervention effects ( column, right side, Table
3
), although of reduced magnitude. The
statistically significant increases in total number of daily servings
persisted when measured by intake recall (0.41; P = .034) but
not by food-frequency questionnaire (-0.04; P = .743). The
effect on servings of fruits largely vanished, while the effect on
servings of vegetables seemed to remain constant when measured by
intake recall (0.24), although not by food-frequency questionnaire
(-0.08). Both knowledge of the Five a Day Program and an opinion
about appropriate number of servings per day showed persistent but
smaller effects (9% and 0.51, respectively).
The same pattern was evident among the diet-related attitudespersistence but shrinkage of short-term effects. The one exception was the appearance of a perception that fruits and vegetables were easy to get at work being more prevalent in the intervention than control groups.
At the end of the 6-month follow-up, statistically significant intervention effects persisted in six of the 15 outcome measures, and one new effect (perception that fruits and vegetables are easy to get at work) emerged. All of these effects were in the expected direction.
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DISCUSSION |
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As we anticipated, the dietary changes produced by the peer education program persisted beyond the conclusion of the intervention. Two previous trials on fruit and vegetable programs using peer education (41) and interpersonal contact from a telephone counselor (42) also showed that changes persisted. Theoretically, peer education achieves persisting change because it alters social group norms that continue to influence individuals after the program is completed. However, recidivism was also evident in our follow-up survey, as witnessed in the telephone-based Five a Day Program (42) and in other nutrition and weight-loss programs (45-50). The effects of peer education interventions may not last indefinitely, and strategies are needed to maintain these changes over longer periods (51) without producing fatigue and boredom that diminish returns (52).
Peer educators were selected in this program on the basis of their centrality in the communication flow within cliques, a more formal, empirical assessment of the "natural helping ability" criteria used to identify lay health advisors in other programs (20,53,54). Peer educators had sufficient regular contact with a large proportion of clique members to deliver the intervention effectively and were respected by co-workers for their opinions and therefore could be opinion leaders. And, by being central within social networks, peer education was implemented in the primary context in which social support is given and received (9), group norms develop (28), and opinion leadership functions (18).
The method of peer education in this program in which education was provided only by lay people and only informally is only one form of peer education. It is an informal counseling function similar to that defined by Eng and Young (9) from the vantage point of being "paraprofessionals" (10,54). Payment was provided to compensate peer educators for time in training, for travel, for interacting with researchers, for keeping records, and for adding a new task to their job.
The conclusions about the effectiveness of peer-led nutrition education in the workplace is limited to nonmanagerial and labor and trades employees. It is not clear from this evaluation whether it will be successful in other work environments, where people from different levels of the authority structure work together in the same groups, i.e., executives, managers, professional staff, and secretaries (28,55).
A second limitation is that fruit and vegetable intake was measured through self-reports rather than by direct inspection of food consumption (56). Self-reports can be biased by demand effects (employees knew that the goal was to increase their intake and therefore reported it) and social desirability tendencies (employees may have felt they looked more attractive by agreeing with the interviewers). Food-frequency questionnaires are more prone to bias than 24-hour intake recalls (57). The increase on both measures and the fact that the 24-hour recall showed larger changes in intake and detected the persisting but smaller change at follow-up suggest that the improvements in consumption estimated by our measures were real.
Another limitation is that group-level estimates of intake for each clique from the 24-hour intake recalls were derived from measures of a single day at each survey, which inflated the variation in the observed group means. We were limited to a single-day measure to obtain permission from employers to interview employees on work time to improve response rates. One analysis (58) did show that averaging 24-hour intake recalls across members of a group, as we did, produced lower variation in group-level means than would have been observed had the average been based on individuals.
The unique aspects of this studythe focus on potentially overlooked workers, the participation of predominantly men in a nutrition peer education program, a design using careful randomization of informal social networks as the unit of analysis, and the collection of follow-up datamake it an important contribution to the literature on lay health advisors. While the dietary changes could be considered small, a dose-response relationship has been observed between fruit and vegetable intake and reduction in the risk of cancer (1,59), so incremental increases of this size should have a meaningful public health impact. Peer education can be applied in many circumstances, including the work environment, where informal groups of individuals are present and significantly influence the behavior of their members.
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NOTES |
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Supported by Public Health Service grant CA59726 from the National Cancer Institute, National Institutes of Health, Department of Health and Human Services.
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Manuscript received December 28, 1998; revised June 10, 1999; accepted July 6, 1999.
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