Summary
Because studies or clinical experiences are ranked both by
strength of design and importance of endpoint, a given study would have
a two-tiered ranking (e.g., 1iiA for a nonblinded randomized study
showing a favorable outcome in overall survival and 3iiiDiv for a
phase II trial of selected patients with response rate as the outcome).
In addition, all recommendations must take into account other issues that
cannot be so easily quantified, such as toxicity, width of confidence
intervals of observations, trial size, quality assurance in the trial,
and cost. Nevertheless, the PDQ ranking system provides an ordinal
categorization of strength of evidence as a starting point for
discussions of study results.
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