Bias may be institutionalised in some places, or may just be harder to detect in others. The reason randomisation schedules for patients are often described as being enclosed in metallised envelopes is because people have been known to X-ray envelopes to break the code before allocation. The inference is obvious. Quality is much more important than quantity. No matter how many trials of inadequate or biased design we have, they do not match up to one trial of adequate size and methodological rigor.
Quality is first, and everything else is nowhere.
It applies to all therapies. A Vickers, N Goyal, R Harland, R Rees. A systematic review of controlled trials.