Research designs in interventional pain management: is randomization superior, desirable or essential?

In the hierarchy of research designs, the results of randomized, controlled trials are considered to be evidence of the highest grade, whereas observational studies are viewed as having less validity because they reportedly overestimate treatment effects. This hierarchy approach to study design has been promoted widely in modern medical literature; in spite of overwhelming evidence that evidence-based medicine includes all types of evidence, and randomized, double-blind studies should not necessarily be considered to represent the best available evidence. In fact, randomized, double-blind studies face insurmountable challenges in interventional pain management. The value of the so-called gold standard of randomized, double-blind trials has been questioned. This study was undertaken to evaluate if randomization does provide the protective statistical shield that some think it provides in an interventional pain management population. In this study we compared randomized and non-randomized samples. Randomization was accomplished by the use of random number tables and random sampling into four groups, three or two groups. Non-randomization was achieved by allocation into various groups by two different means. The results of this evaluation showed that there was only one significant difference when patients were allocated by means of non-randomization among the groups or compared to the total sample. In contrast, randomization showed significant differences in seven parameters. The results of this study conclude that in interventional pain management settings, non-randomized sampling is valid.