The Journal of Bone and Joint Surgery 82:838 (2000)
© 2000 The Journal of Bone and Joint Surgery, Inc.
Challenges in Evaluating Patients Lost to Follow-up in Clinical Studies of Rotator Cuff Tears*
Barbara M. Norquist, B.S. ,
Benjamin A. Goldberg, M.D. and
Frederick A. Matsen, III, M.D.
Investigation performed at the Department of Orthopaedics,
University of Washington, Seattle, Washington
*No benefits in any form have been received or will be received
from a commercial party related directly or indirectly to the subject
of this article. Funds were received in total or partial support
of the research or clinical study presented in this article. The
funding sources were the Orthopaedic Research and Education Foundation,
the Bristol-Myers Squibb/Zimmer Institutional Award for Excellence
in Orthopaedics, and the E. A. Codman Research Fund at the University
of Washington.
Department of Orthopaedics, University of Washington, Box 356500,
1959 N.E. Pacific Street, Seattle, Washington 98195-6500. E-mail address
for F. A. Matsen, III: matsen{at}u.washington.edu
Background: Long-term follow-up studies
are necessary to critically evaluate the outcome of a treatment
intervention for a specific disorder. However, patients may cease
participating in a long-term study and become lost to follow-up;
thus, their current condition is unknown. The underlying characteristics that
predispose a patient to become lost to follow-up are difficult to
identify and control. Patients who are lost to follow-up may be
contacted by telephone; however, the effect of administering a functional
assessment questionnaire by telephone compared with that of mailing
a questionnaire is unknown. The purpose of this study was to compare
patients who continued to respond to requests for follow-up with
those who did not. A second purpose was to compare responses obtained
by mail with those obtained by telephone interview.
Methods: Two hundred and twenty-four patients
with a rotator cuff tear were enrolled in an ongoing study of shoulder
function and general health. Self-assessment questionnaires were
mailed to every patient at six-month intervals. Sixty-seven patients (30
percent) regularly responded to mailings (identified as responders
in this study), fifty-five patients (25 percent) responded occasionally (these
patients were not included in the analysis), and 102 patients (46
percent) ceased to respond and became lost to follow-up (identified
as nonresponders in this study). This investigation was performed
to determine: (1) the characteristics of nonresponders compared
with those of responders, (2) the functional status of nonresponders
as assessed with a questionnaire over the telephone, and (3) the
effect of administering a self-assessment functional questionnaire
by telephone compared with that of sending the same questionnaire by
mail.
Results: Nonresponders tended to have lower
initial scores for the mental health summary (p = 0.03) and for social
function (p = 0.01), were less likely to have had surgery (p = 0.009),
and were less likely to consume alcohol (p = 0.03). At the last
known time when they completed the mailed questionnaire, nonresponders
reported significantly worse shoulder function than responders (p
= 0.0001). However, on telephone questioning the mean number of
shoulder functions that the nonresponders indicated that they could
perform was greater than the mean number documented on their last
mailed questionnaire (p < 0.0001). In a random subgroup of responders,
the mean number of functions that the patients indicated that they
could perform when interviewed by telephone was significantly greater
than the number indicated on their most recent mailed questionnaire
(p < 0.01). The results obtained by telephone from this random
subgroup of responders were similar to those obtained by telephone
from the nonresponders.
Conclusions: There are differences between patients
who continue to participate in a study and those who become lost
to follow-up. Functional assessment questionnaires administered
by telephone yield different results than the same questionnaires
sent by mail. These considerations are relevant to the design, implementation,
and interpretation of clinical studies in which functional questionnaires
are used.

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