| | What
is your interpretation?
You answered:
The study should be replicated with the inclusion of a questionnaire
to examine whether patients and research staff can guess what
the treatment assignment is.
PERHAPS.
THIS IS CONTROVERSIAL
Many experts have recommended that patients and research
staff be asked to guess the identity of treatments as a
test of blinding (Moscucci
et al., 1987). Few investigators have done this, however,
perhaps because of fears that a finding that a study is
incompletely blinded will be used to discredit their positive
results. In addition, an accurate test of blinding is hard
to obtain. For example, patients may correctly guess whether
they are active treatment or placebo by noting the presence
or absence of therapeutic response. This would occur in
a perfectly well blinded study, and it would not be fair
to discount a positive study because patients identified
the medication because of therapeutic effects, not side
effects.
Moscucci
et al., 1987 suggested that one ask patients whether
their guess is based on the occurrence of therapeutic effects
or side effects. However, this distinction is difficult
in pain studies because with most analgesics, pain relief
and side effects begin at the same time. Furthermore, post
hoc explanations of why a person made a certain guess are
notoriously unreliable. Even if the patient says he guessed
"active medication" because of side effects, the
answer may have been influenced by pain relief. Shlay
et al., 1998 suggested a method to partly protect against
this bias by stratifying patients' correct and incorrect
guesses of treatment according to the grade of relief they
reported on a category scale, followed by a contingency
table analysis to test whether correct guesses were more
common than chance.
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