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What
is the most appropriate way to compute the average time
of onset of pain relief and statistically compare the drug
group to the placebo group?
You
answered:
 Calculate
the median time to onset and compare the overall distributions
of the onset times using survival analysis techniques.
CORRECT
Most pain researchers
continue to use means to represent the magnitude of pain reduction because the
distribution of pain scores usually approaches normality and this analysis has
the most power. For the analysis of time of analgesic onset, however, the work
of (Laska
et al., 1991) has generated a consensus that a group of nonparametric techniques
called "survival analyses" are most appropriate. In these methods, adapted
from the analysis of long-term cancer and cardiovascular disease trials, the median
and 25th and 75th percentile scores are used to represent
the group result. Such analysis of analgesic onset and duration is now done routinely
in single-dose studies of new drugs (Lakatos
et al., 1999). The same principles are applicable to chronic treatment of
any disease (Laska
and Siegel, 1995), but have not yet been adopted in chronic analgesic studies.
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