NBSS: Changes were made; suspicious changes were not
Online posting: May 9, 1997
Published in print: August 1, 1997 CMAJ 1997;157:248
Re: The review of randomization in the Canadian National
Breast Screening Study: Is the debate over? [editorial], Dr.
Norman F. Boyd CMAJ 1997;156:207-9 [full text / résumé]
See response by: N.F. Boyd
In this editorial accompanying the article "Randomization in
the Canadian National Breast Screening Study: a review for
evidence of subversion," by Drs. John C. Bailar and Brian
MacMahon (CMAJ 1997;156:193-9 [full text / résumé]
), Dr. Norman F.
Boyd writes "The absence of name alterations had previously been
cited by the NBSS investigators as evidence that randomization
had not been subverted." He cites 2 articles from the National
Breast Screening Study (NBSS). In the context of a review that
has documented several instances of name alterations (the
majority explicable), his statement, if true, would reflect
poorly on NBSS investigators. In fact, Boyd appears to have
misunderstood information from the references and, in the
process, undermined the credibility of NBSS investigators.
NBSS investigators have never reported that name alterations
did not occur among the entries for the 90 000 NBSS participants;
alterations clearly did occur. We have reported that no
suspicious changes in the random allocation sheets had been
identified in the participants who died of breast cancer.
The external review found that, of 97 unexplained alterations
on lines allocating women to mammography, only 1 was associated
with a woman who died of breast cancer, and breast cancer had not
been diagnosed at the first screen in this case. This alteration
was either overlooked by us or detectable only by forensic
experts.
Since most readers have neither the interest nor the time to
check the references cited, I offer citations from the articles
for comparison with Boyd's interpretation of what we reported.
"The original randomization sheets were carefully rechecked,
specifically in relation to women who died; no evidence of any
falsification, erasure or other changes was found."[1]
"The original randomization sheets were re-examined to look
for changes in script or pens used, crossing out of names,
erasures, or problems with date sequences with special attention
given to the records of those who had died of breast cancer. No
suspicious entries were found."[2]
It is important to note the use of the words "re-checked" and
"re-examined." All NBSS randomization sheets were routinely and
carefully examined each month at the national coordinating centre
during the recruitment period.[1,2]
It is unrealistic to expect that written entries could be made
for 90 000 participants without errors requiring correction. The
issue is not whether changes were made but whether suspicious
changes were made. Suspicion, like beauty, is in the eye of the
beholder. Those who are suspicious should demand equal scrutiny
of random allocation procedures in all screening trials.
Cornelia J. Baines, MD
Co-Principal Investigator
National Breast Screening Study
Department of Preventive Medicine and Biostatistics
University of Toronto
Toronto, Ont.
References
- Miller AB, Baines CJ, To T, Wall C. Canadian National
Breast Screening Study: 1. Breast cancer detection and death
rates among women age 40 to 49 years [published erratum appears
in CMAJ 1993;148:718]. CMAJ
1992;147:1459-76.
- Baines CJ. The Canadian National Breast Screening Study: a
perspective on criticisms. Ann Intern Med
1994;120(4):326-34.
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