Download Factors associated with attrition from a national bone

Bone Marrow Transplantation, (1999) 24, 313–319
 1999 Stockton Press All rights reserved 0268–3369/99 $12.00
http://www.stockton-press.co.uk/bmt
Factors associated with attrition from a national bone marrow registry
GE Switzer1,2, MA Dew2,3,4, AA Stukas2, JM Goycoolea2, J Hegland5 and RG Simmons2,6
Departments of 1Medicine, 2Psychiatry, 3Psychology, 4Epidemiology and 6Sociology, University of Pittsburgh; and 5Director of
Scientific and Technical Services, National Marrow Donor Program, Pittsburgh, PA, USA
Summary:
During its 10-year existence, the National Marrow
Donor Program (NMDP) has been extremely successful
at recruiting potential bone marrow donors to join the
volunteer registry. Due in part to successful recruitment
and the longevity of the registry, the focus of the NMDP
has now shifted to decreasing potential attrition when
volunteers are recontacted for additional testing to
determine whether they would be the optimal donor for
a specific patient. Our own interest in the bone marrow
donation process led us to examine four domains of
variables – demographic characteristics, volunteer history, recruitment-related characteristics and donationrelated concerns – that we hypothesized would be associated with increased likelihood of donor attrition at a
key donor decision-point (DR-stage blood typing). Questionnaires were mailed to potential donors after they
were contacted at the DR-stage, and had made the
decision of whether or not to continue with blood
typing. Our final sample included 756 volunteers who
decided to continue with typing, and 258 individuals
who declined further participation in the registry. In
the bivariate analyses, factors in three of the four
domains (all except demographic characteristics) were
found to be substantially correlated with likelihood of
attrition. Logistic regression indicated that nine central
variables across the three domains produced the
majority of increased attrition likelihood. Finally, a
dose-response analysis suggested that as the number of
attrition-related factors endorsed by an individual
increased, his/her likelihood of dropping out of the
registry also increased. Implications for future research
and interventions to reduce potential donor attrition
are discussed.
Keywords: bone marrow donors; attrition; retention
The National Marrow Donor Program (NMDP) was
founded in 1987 to develop a nationwide registry of potential bone marrow donors. Because many patients ill with
blood-related disorders cannot find an adequate marrow
match among family members, the NMDP established a
target goal of registering 100 000 unrelated potential donors
who would be available to donate marrow as needed. Now,
Correspondence: Dr G Switzer, University of Pittsburgh, Department of
Medicine, 3811 O’Hara Street, Pittsburgh, PA 15213, USA
Received 6 July 1998; accepted 23 December 1998
10 years later, the NMDP registry has exceed all expectations and is growing at a rate of 20 000–30 000 new volunteers per month, with total registry size of more than
3 million.1
Although scientists and biostatisticians working with the
NMDP have recognized that a relatively large number of
registered volunteers is necessary to adequately represent
the full range of human leukocyte antigen types (HLA: protein markers used for matching two individuals’ bone
marrow) found in the US population, the continued rapid
growth of the registry has shifted attention from emphasis
on donor recruitment to the retention of potential donors
who are already on the registry. Donor retention has
become increasingly important as the registry matures,
especially given the fact that more than a quarter of those
registered may, for a variety of reasons (eg declined further
testing, medically deferred, unreachable, temporarily
unavailable), be unavailable when actually called upon to
undergo further blood testing toward donation.1 Although
the exact impact of donor attrition is difficult to quantify
because patients who search the registry in a preliminary
manner and find only a few potential matches may seek
other forms of therapy and because there are multiple points
at which potential donors may decline further testing, both
the NMDP and its funding agencies agree that improving
donor retention is crucial.
The critical importance of ensuring that potential donors,
when contacted, will agree to undergo further blood testing
leading to donation led us to examine registrant characteristics that might be related to this decision. Specifically, we
were interested in whether those who continued with testing
(volunteers) differed from those who declined further testing (nonvolunteers) along four key dimensions: demographics, history as a volunteer in general, registry recruitment issues and donation-related concerns. Although there
is a growing body of literature concerning the physical and
psychological consequences of unrelated donation,2–6 as
well as research examining individuals’ willingness to join
the registry and to (hypothetically) agree to donate,7–9 there
have been no studies that examine psychosocial issues associated with demonstrated willingness to continue with testing when volunteers are actually recontacted for a
specific patient.
Most potential donors join the registry by donating a
small blood sample that is then partially HLA typed and
listed on the computerized registry. A patient searching the
registry may identify several potentially matched registrants
and request that they undergo further blood typing (DRstage testing). Potential donors are then contacted, informed
that they are a potential match, and asked whether they are
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GE Switzer et al
314
still interested in donating. This contact point is important
for several reasons, including the fact that it is often the
first contact that donors have had with the NMDP since
joining the registry (sometimes many years earlier), as well
as the fact that most potential donor attrition occurs at this
stage. Only the more committed individuals reach the later
typing stages.
Thus, the goal of current effort was to determine which
potential donor characteristics were related to the decision
of whether or not to continue when contacted for DR-stage
blood typing. In addition to examining potential donor
demographic characteristics, we gathered information on
three classes of psychosocial variables that previous
research and anecdotal evidence suggest may be related to
continued registry participation; the evidence for each class
of variables is summarized below.
Volunteer history
In general, we expected that individuals who volunteered
in settings other than bone marrow donation would be more
likely to continue with blood testing. Studies conducted
with blood donors, as well as studies with bone marrow
donors indicate that individuals with a history of volunteerism, may develop an internal self-image consistent with
helping others, and thus may be more committed, and/or
less ambivalent toward volunteering. For example, in a
classic set of investigations, Piliavin and colleagues10,11
demonstrated that first-time blood donors who did not have
predonation altruistic self-images, often developed an
intrinsic commitment to blood donation after subsequent
donations. Our own research with bone marrow donors suggests that commitment to blood donation may generalize to
other forms of medical volunteerism; we have found blood
donors to be less ambivalent about the prospect of their
upcoming bone marrow donation than were their non-blood
donor counterparts.6 Thus, we anticipated that registry
members with any history of volunteering, and more
specifically, with a history of blood donation would be less
likely to drop out of the registry at DR-stage typing. In
addition, we hypothesized that individuals who had joined
the bone marrow registry more recently – because their
decision to help by donating marrow was more salient –
would be less likely to drop out of the registry than those
who had joined in the more distant past.
Recruitment issues
The theme of commitment to the donation process demonstrated by previous volunteerism may also may be central
to the context in which individuals are recruited to the
registry and, in turn, to later decisions about donating. For
example, we expected that individuals who exhibited early
ambivalence by delaying the decision to join the registry,
or who were discouraged by others from joining, would
be more likely to drop out later. Conversely, those who
demonstrated some further interest in the process by consulting friends and family or medical professionals, or who
were spontaneously encouraged by others to join the registry should be less likely to drop out.
We expected that individuals recruited in contexts that
appeared to involve social pressure to join the registry – in
contrast to contexts that evoked more intrinsic commitment – would be more likely to later drop out than their
counterparts. The NMDP recruits prospective donors in a
variety of manners, including community, minority, university and corporate drives, drives focused on a specific
patient in need of a transplant, and individually, at blood
donation centers. In the context of marrow donation, potential donors who joined with other people instead of individually, who joined for a specific ill patient (typically at
a community drive in conjunction with friends and
neighbors), or who joined because of their membership in
a particular ethnic group, might be expected to be less committed to the process than those who initiated registry membership individually. Studies of volunteerism and altruistic
behavior in a variety of contexts have demonstrated that
external social pressures to help others can undermine
intrinsic commitment to help, and cause volunteers to discontinue their participation sooner, or at higher rates than
volunteers who did not experience such pressures.11–13
We also expected that, in addition to the conditions under
which individuals joined the registry, their stated motives
for joining would also be associated with the likelihood
they would drop out of the registry later. Previous research
has demonstrated that motives are related to continued volunteerism or to feelings about participation in volunteer
activities among volunteer ‘buddies’ for AIDS patients,14,15
4-H volunteers,16 social service volunteers,17 elderly volunteers,18 kidney donors4,19 and bone marrow donors.20 Volunteers who are intrinsically motivated to join the marrow
registry (eg by their commitment to religious or ethical
precepts), should be less likely to drop out as compared to
those who are extrinsically motivated (eg by their empathic
focus on a specific patient).
Donation-related concerns
Our final domain of interest included medical, as well as
more general, concerns about the donation process. We
anticipated that potential donors with greater numbers of
concerns would be more likely to drop out of the registry
then their less concerned counterparts. Anecdotal accounts
from bone marrow donor coordinators suggest that potential donor fears and concerns are often cited as the reason
for declining to continue with blood testing. Similar factors
are also associated with nondonation among potential
blood donors.11,21
Methods
Study participants and procedure
Forty of the approximately 100 US donor centers were
initially selected to participate in the study based on their
geographic location, and the total number and ethnic background of volunteers on their registries. Our goal in sel-
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GE Switzer et al
ecting centers was to ensure that our sample represented
the total registry network on each of these three variables.
We began with the 40 donor centers that had previously
participated in other research and demonstration projects
for the NMDP. Using a stratified random sampling procedure, we added and/or deleted centers until we achieved
a total sample of 40 centers that matched the overall registry on the three stratifying variables. Four centers declined
to participate when they were initially approached and were
replaced with centers with similar characteristics. Two
other centers merged several months into the study and,
thus, we ended with a final sample of 39 centers.
Potential study participants included all registry members
at the 39 donor centers who (1) preliminarily matched an
ill patient between 1992 and 1996; and (2) either agreed
(volunteers) or declined (nonvolunteers) to undergo further
blood testing (DR-stage typing) to confirm the match. Other
potential donor groups (eg medically deferred, unreachable,
temporarily unavailable) – approximately 15–20% of the
total number of potential donors requested for DR-stage
typing each year – were not included in the sampling frame.
Although our sample included only potential donors who
specifically declined further testing – because they represent the clearest example of refusal to participate – anecdotal evidence from donor coordinators suggests that (1)
potential donors who do not return telephone calls about
testing; (2) those who indicate some medical difficulty that
would preclude donation; and (3) those who indicate that
they are currently unavailable, may also be expressing
reluctance to participate and thus be similar in many ways
to those who specifically refuse. During the course of the
study, the number of potential donors who were contacted
to undergo further blood testing and met criteria for our
sampling frame averaged approximately 1000 per month.
On average, 90% of the total monthly sampling frame were
volunteers and 10% were nonvolunteers. To select individuals to receive our questionnaire, we used a random sampling procedure, stratified to ensure adequate representation
of potential donors from smaller centers and ethnic minority groups. Nonvolunteers were sampled at a much higher
rate than were volunteers to ensure that the data collection
period would be similar for both groups.
Individuals sampled using this procedure fell into two
groups based on whether or not they had given a priori
consent (via the informed consent form for joining the
registry) to be contacted to participate in other related
research projects such as ours. When individuals joined the
registry, they could check a box signifying that they would
be willing to be contacted about other scientific projects
related to bone marrow donation. Only those who had
agreed to be contacted became part of our initial sampling
frame. Approximately 10% of the sampling frame had not
given permission to be contacted for other projects, and
were thus excluded from our sampling frame.
Questionnaires, consent forms, and a cover letter
explaining the study were mailed to donor centers where
the sampled registry members (identified to us only by
center ID numbers) were registered. Donor coordinators at
each center then affixed an address label and mailed the
packet to the potential donor. This relatively complex mailing procedure enabled us to adhere to NMDP confiden-
tially conventions which suggest that only local donor centers should have access to the names and addresses of
potential donors. Subjects who did not respond to the initial
mailing within 2 weeks were sent a reminder postcard, and
after 2 more weeks, received a second full packet.
As we anticipated at the outset of the study, response
rates for volunteers (62%) and nonvolunteers (16%) were
quite different. Because nonvolunteers had made a decision
not to continue participation in the registry, we had
expected that it would be difficult to secure their participation in a study related to their past roles as NMDP registry members. Despite our use of the state-of-the-art mailed
survey techniques demonstrated to improve response rates
(eg repeated follow-up mailings, persuasive cover letter,
and monetary and nonmonetary incentives), the response
rate for nonvolunteers remained relatively low. We consider the interesting difficulties of securing participation of
resistant populations further in the Discussion section.
However, we were able to determine that among nonvolunteers, response rates differed only slightly across ethnic
groups (ranging from 9% for Hispanics to 17% for
Caucasians), length of time on the registry, and by donor
center (for those centers that sent at least 10 nonvolunteer
–
packets, response rates ranged from 10% to 30%, X = 17%,
interquartile range = 12%–20%).
Measures
The central study outcome was whether potential donors
decided to continue with testing or to decline further participation in the registry when contacted for DR-stage blood
typing. Other measures are described in detail below.
Volunteer history: Volunteer history was assessed with a
combination of questionnaire items and data extracted from
the NMDP database. Current volunteerism in general settings, excluding blood donation, was assessed with a single
item asking respondents if they were currently active in any
volunteer work (0 = no, 1 = yes). History of blood donation
was also assessed with a single item asking whether they
had ever been a blood or apheresis donor (0 = no, 1 = yes).
The length of time that respondents had been members of
the NMDP registry was extracted from the NMDP database
and dichotomized (0 = member for less than 4 years, 1 =
member for 4 or more years). The midpoint of 4 years was
chosen as the cutpoint because at the time the study started,
the registry had been in existence for 8 years.
Recruitment-related issues: Five items were used to assess
respondents’ decisions to initially join the registry. We
asked whether they had delayed the decision to join (0 =
no, 1 = yes), whether they had consulted family/friends or
professionals before deciding to join (0 = no, 1 = yes), and
whether they had been spontaneously encouraged (0 = no,
1 = yes) or discouraged (0 = no, 1 = yes) from joining.
Three items assessed characteristics of the recruitment
setting, including whether other potential registrants were
present when respondents joined, whether they joined at a
drive focused on a specific patient, and whether their own
ethnicity played a role in their decision to join (all coded
0 = no, 1 = yes).
315
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GE Switzer et al
316
Finally, motives for joining the registry were assessed
using an open-ended question asking respondents to
describe their reasons for originally volunteering to be bone
marrow donors. Responses to this question were assigned
to one of five motive categories based on Simmons’ prior
work with kidney donors,4,19 and utilized in our own previous studies of bone marrow donors.20 Thus, motives were
coded as (1) empathy-related if they focused on respondents’ feelings toward the recipient; (2) idealized helping if
they indicated ‘automatic’ responding without deep thought
about the potential costs of donation; (3) social or religious
obligation if they focused on feelings that donating was a
social or religious/moral obligation; (4) exchange-related if
they stated or implied an awareness of the relative costs
(to themselves) and benefits (to themselves or the marrow
recipient) of donating; (5) expected positive feeling if they
focused on the good feeling it gave them to join the registry
(see Ref. 20 for a complete description and examples of
each motive category). Although some respondents indicated multiple motives for joining the registry, assignment
to motive categories was based on the first motive listed (0
= motive not endorsed, 1 = motive endorsed).
Donation-related concerns: Medical and general concerns
about the donation process were assessed by asking respondents to endorse any of a list of possible concerns. Medical
concerns included physical pain, damage to the donor’s
own health, anesthesia side-effects, and fear of needles (0 =
item not endorsed, 1 = item endorsed). General nonmedical
concerns included missing time from work, that family
would worry, that the patient’s chances of survival were
low even with donation, that the donor would have no control over who received his/her marrow, and that marrow
donation was against the donor’s religious beliefs (0 = item
not endorsed, 1 = item endorsed).
Analytic strategy
The analysis was conducted in three phases. First, we
examined the proportions of volunteers and nonvolunteers
who possessed each of the predictor characteristics across
four domains: demographic, volunteer history, recruitmentrelated and donation-related. We computed odds-ratios to
determine whether having a given characteristic increased
the likelihood of registry attrition. Next, we used multivariate logistic regression to examine the unique impact of each
factor on registry attrition, controlling for other factors. In
order to be appropriately conservative and limit the risk of
type I error, attrition-related factors were allowed to enter
this regression analysis only if their bivariate relationship
with attrition was at least modest in size (effect size,
Cohen’s h ⬎ 0.2022), and if the attrition-related factor was
sufficiently prevalent to include in multivariate analyses (ie
occurred in at least 15% of the sample). Finally, we conducted a dose-response analysis to ascertain whether possessing an increasing total number of attrition-related factors compounded an individual’s likelihood of attrition
from the registry.
Results
Factors associated with donor attrition
Percentages of volunteers and nonvolunteers who possessed
each of the characteristics within each of the four study
domains and odds-ratios indicating which donor characteristics led to increased likelihood of attrition are presented
in Table 1.
None of the potential donor demographic characteristics
were reliably associated with increased likelihood of registry attrition. However, variables from each of the other four
domains were associated with higher attrition. In terms of
volunteer history, blood donors were less likely to drop out
of the registry, and those who had been members of the
registry for longer than 4 years were significantly more
likely to discontinue participation. Virtually all the recruitment-related issues were associated with attrition. Those
who delayed the decision or were discouraged from joining
were more likely to drop out of the registry, while those
who consulted relatives or professionals were less likely.
Individuals who joined with others, joined at a drive for a
specific patient, or reported that their ethnic group mattered
in their decision of whether to join the registry were all
more likely to discontinue registry participation. Those who
reported empathy motives were more likely to drop out,
while those who reported social/religious, exchangerelated, or expected positive feeling motives were less
likely to drop out of the registry. Finally, all medical and
general concerns about the donation process – except that
one’s family would worry – were associated with increased
likelihood of discontinuing registry membership.
Fourteen variables that met our a priori criteria of showing at least modestly-sized associations with attrition, and
occurring in more than 15% of the total sample were
entered into a logistic regression analysis to examine their
unique effects on potential donors’ DR-stage status
(volunteer/nonvolunteer). Predictors were entered hierarchically in three blocks corresponding to their hypothesized temporal relation to the outcome; volunteer history,
recruitment-related issues, and donation-related concerns.
Results of the logistic regression are presented in Table 2.
Both block I attrition-related factors remained strongly
associated with attrition; blood donors were less likely, and
those registered longer were more likely, to drop out of the
registry. All block II attrition-related factors except joining
at a drive for a specific patient and having empathy or
social/religious motives for joining predicted increased
attrition above and beyond block I predictors.
Finally, among block III factors, concerns about damage
to the donor’s health and time missed from work for the
donation predicted attrition even after block I and II predictors were accounted for. As shown in Table 2, each block
of factors produced a significant improvement in model fit
over the preceding model (ie the model without the justadded block of variables). The final model that included all
variables provided a good overall fit to the data.
Finally, we conducted a dose-response analysis to determine if the presence of increasing numbers of attritionrelated factors within a given respondent was associated
with enhanced likelihood of discontinuing registry member-
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GE Switzer et al
Table 1
317
Factors associated with donor attrition
Nonvolunteer (n = 258)
Volunteer (n = 756)
Demographic characteristics
% Women
Mean age
% Not married
% No children
% College degree
% Not employed
% Non-white
59
36
37
36
45
18
18
57
37
36
34
40
14
23
1.09
1.88 (t-value)
1.02
1.05
1.27
1.37
0.73
Volunteer history
% Volunteer elsewhere
% Blood donor
% ⬎4 years on registry
42
58
41
40
77
10
1.09
0.42***
6.25***
61
58
23
23
47
46
64
33
30
31
1.85***
0.78
0.59**
0.68*
1.94***
58
68
36
42
52
17
1.85***
1.98***
2.70***
34
19
12
4
2
24
20
19
14
5
1.39**
0.97
0.62**
0.31***
0.36*
68
59
47
35
59
30
36
20
1.48***
3.28***
1.58***
2.22***
56
41
12
14
2
34
35
7
3
1
2.53***
1.29
1.84*
4.79***
6.03***
Donor factor
Recruitement-related characteristics
Deciding to join
% Delayed decision
% Consulted friends/family
% Consulted professional
% Encouraged to join
% Discouraged from joining
Recruitment setting
% Joined with others
% Drive for patient
% Ethnic group mattered
Motives for joining
% Empathy
% Idealized helping
% Social/religious
% Exchange
% Expect positive feelings
Donation-related concerns
Donor medical concerns
% Pain
% Damage own health
% Anesthesia
% Needles
Donor general concerns
% Time off work
% Family would worry
% Patient’s chances low
% Who gets marrow
% Against religion
Odds-ratio
*P ⭐ 0.05; **P ⭐ 0.01; ***P ⭐ 0.001.
ship. Study participants were grouped into four ordinal categories based on the number of attrition-related factors that
each person had (0–1, 2–3, 4–6 and 7–9 factors). Only factors that significantly predicted attrition in the logistic
regression analysis were used for this analysis.
As illustrated in Figure 1, the logistic model indicates
that a strong dose effect exists (B = 1.25; standard error =
0.11; goodness of fit chi-square (3, n = 1014) = 0.65, P =
0.72; improvement over the null hypothesis of no effect:
chi-square (2, n = 1014) = 150.78, P ⬍ 0.001). Thus, as
the number of factors possessed by a given individual
increased, the likelihood that he/she would drop out of the
registry also increased dramatically.
Discussion
Our central aim was to examine potential attrition-related
factors for attrition from a national bone marrow donor
registry. One of the most striking findings was the modest
association of demographic characteristics with attrition,
and the relatively greater importance of psychosocial
characteristics in determining whether potential donors continued with blood testing. Several of the variables in each
of the four psychosocial domains were associated with
increased likelihood of attrition in both the univariate and
multivariate analyses.
Realistic commitment to volunteerism, and to bone marrow donation specifically, emerged as one of the unifying
themes of our multivariate analyses. As we had expected,
two aspects of volunteer history – whether or not the individual was a blood donor, and the length of time that he/she
had been a bone marrow registry member – were highly
predictive of donor attrition. Potential donors who
responded that their ethnic group was an important factor
in the decision to join the registry also dropped out of the
registry at higher rates. We had hypothesized that citing
one’s ethnic group as a reason for joining the registry might
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GE Switzer et al
Table 2
Unique effects of potential attrition-related factors on
donor attrition: odds-ratios from logistic regression analysis
Odds-ratio
Block I predictorsa
Blood donor
⬎4 years on registry
0.42***
5.56***
Chi-square improvement over null (df = 1)
95.78***
Block II predictors
Delayed decision
Consulted professional
Discouraged from joining
Joined with others
Drive for patient
Ethnic group mattered
Empathy motives
Social/religious motives
1.59*
0.52**
2.27***
1.56*
1.07
2.08***
1.45
0.78
Chi-square improvement (df = 6)
55.37***
Block III predictors
Damage own health
Anesthesia
Needles
Time off work
2.70***
1.02
1.33
2.56***
Chi-square improvement (df = 3)
58.99***
Chi-square for full model (df = 13)
844.52
a
Variables included in the logistic regresssion had effect sizes (h)
greater than 0.2, and occurred in more than 15% of the sample.
70
Percent with given
number of factors
318
60
50
40
30
20
10
0
0–1
2–3
4–6
7–9
Total number of factors
Figure 1 Likelihood of potential donor attrition by number of factors
endorsed.
indicate extrinsic social pressure, or even a lack of understanding of the nature of joining a registry of this sort,
rather than internal commitment to donation. In addition,
variables that might be related to ambivalence about donating – delaying the decision to join the registry and having
been discouraged from joining – were associated with
greater attrition likelihood. Finally, those who demonstrated
commitment to the process by taking the additional step of
consulting a health professional were less likely to drop out
of the registry. Each of these psychosocial variables is an
important indicator of some aspect of commitment to bone
marrow donation: past behavior, reasons for joining the
registry, others’ reactions, and current attitudes.
In addition to variables related to commitment to
donation, two ‘donor concerns’ variables were also associa-
ted with attrition in the multivariate analysis. Individuals
who were concerned that the process might damage their
own health, and those who were concerned about the time
that they would miss from work were more than twice as
likely to drop out of the registry than individuals who did
not express these concerns. Somewhat surprisingly, concern
about undergoing anesthesia – which is probably the most
risk-laden part of the donation process – did not produce
elevated attrition likelihood in the multivariate analysis.
These findings have several implications for the recruitment and retention of potential bone marrow donors, as
well as other types of medical volunteers. First, the lack of
significant demographic effects, and the substantial number
of psychosocial/contextual effects suggests that there is
ample room for interventions targeting donor retention.
Given our findings, it seems important to design recruitment settings that (1) reduce ambivalence about joining,
perhaps by providing additional informational material or
opportunities for discussion; (2) shield potential donors
from social pressure to join; and (3) foster intrinsic commitment to donating. Additionally, both at recruitment and
when potential donors are contacted for DR-typing, special
effort should be made to allay medical and work-related
concerns.
As was noted in the Methods section, the relatively low
response rate among those who dropped out of the registry
is one of the limitations of this study. We had anticipated,
and did find, that individuals who declined to continue as
registry members were less likely to complete a questionnaire about their experiences. Our ability to secure participation from nonvolunteers was further constrained by the
fact that registry members – and nonvolunteers – were
guaranteed anonymity to everyone except their local donor
center. Thus, our questionnaire packets were mailed to nonvolunteers from their local center, perhaps causing misunderstandings about the sponsors and purpose of the questionnaire. Furthermore, we were unable to directly contact
potential study participants by telephone either before or
after mailing the packet. Prenotification and telephone follow-up are proven techniques for improving response
rates.23–25 Once we had confirmed that we were indeed
obtaining low response rates among the nonvolunteers, we
implemented several procedures, including revising the
cover letter to be more persuasive, and offering a variety
of incentives, to encourage registry members to complete
the questionnaires. These procedures elevated response
rates by approximately 8%. Despite this improvement in
return, we suspect that nonvolunteers who returned their
questionnaires may be somewhat different than those who
did not. The direction of such differences is difficult to
specify, although it seems unlikely that nonvolunteer nonrespondents would have had higher levels of commitment, for
example, than nonvolunteer respondents. Hence, it seems
unlikely that our analyses have overestimated the impact
of this category of psychosocial variables on the outcome.
Nevertheless, because we cannot determine exactly how
respondents might differ from nonrespondents, it will be
important to confirm our findings in other samples of registry nonvolunteers.
In conclusion, this study is the first to examine the
relationship of potential marrow donor characteristics to the
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GE Switzer et al
decision of whether or not to continue with the process
leading toward possible donation. The findings indicate that
key psychosocial variables are linked to increased likelihood of attrition from the registry and suggest that intervention strategies targeting these variables both at recruitment and at later contact points might be effective in
enhancing donor retention. For example, interventions that
encouraged newly recruited donors to participate in other
types of medical donation (eg blood donation) might in turn
foster enhanced commitment to the registry.
More thorough education of new recruits, more selective
recruiting procedures designed to provide reluctant volunteers a opportunity to ‘opt-out’ of joining the registry, and
asking the potential donor a few questions about how his
friends/family feel about donation may all be cost-effective
ways of creating a highly committed registry of volunteers.
Although we cannot provide specific cost-benefit figures for
implementing such interventions rather than simply
recruiting additional volunteers, it is clear that the monetary
cost of recruiting a volunteer, drawing blood, sending the
blood for HLA typing, and entering the typing on the
NMDP registry will exceed the small extra costs involved
in most of these interventions. In addition to the monetary
savings that might be realized by enhancing retention,
potential psychological costs to the patient for whom registered and matched volunteers may not be available will be
reduced. Finally, potential psychological costs such as guilt,
regret, or lowered self-esteem to potential donors who
decline further testing may also be attenuated.
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Acknowledgements
This work was supported by grant HL48883 from the National
Heart, Lung, and Blood Institute, Bethesda, MD, USA.
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