Welcome to the Inquiry Podcast from the BBC World Service.

Each week we bring you four expert witnesses answering one pressing question from the news. Dr Vigniac Prasad, like many doctors, is followed by ghosts. Early in his training he worked on a cardiac intensive care unit where a common

procedure was to insert a stent, a tube that can open narrow or blocked arteries.

For some conditions this was life saving.

For others, we now know that Stents did nothing to help.

Dr Prasad remembers one woman in particular for whom it was probably useless and she suffered

tragic complications.

Today he writes about how medical science changes its mind. He reckons that maybe 40% of medical procedures are either useless or positively do harm.

Frequently he says because the science wasn't done properly in the first place. In fact, all across the research world

there's been sudden humbling evidence of what some academics call a crisis of

credibility. By one estimate, most published research is false.

When we devote huge effort in the knowledge factory in universities and elsewhere

to advancing the knowledge we all depend on that raises awkward questions. I'm Michael Blasland. A question this week on the

inquiry, is the Knowledge Factory broken? College Factory, broken. Part 1. It doesn't stand up.

I fell into this by mistake in truth.

For 10 years I was the head of the Hematology oncology research group at Amgen,

a biotech company based in California.

In 2012 at his former company, what Glenn Begley proposed sounded harmless enough.

To sum up what Amgen knew, what worked and what hadn't in his area of research.

He also set out to reproduce the work of other scientists in the field to ensure it was correct.

And although my rule of thumb had been that half of the literature was wrong,

and that was really just based on 20 years of living and breathing research

...