Wrt overdiagnosis of asthma:
www.nhs.uk/news/2015/02February/Pages/Is-asthma-being-over-diagnosed.aspx
So, where did the figure of 1 million come from? All the UK press rallied round a statement in the draft guideline that said: “studies of adults diagnosed with asthma suggest that up to 30% do not have clear evidence of asthma”. What followed was clearly a “back of the envelope” calculation extrapolating this to the number of people receiving treatment for asthma in the UK, which is around 4.1 million. This gave the magic figure of 1.23 million potentially misdiagnosed people.
Unfortunately, the 30% figure in the draft guideline is not referenced, so we can’t find out how accurate it is. We also don’t know whether it applies to specific asthma subgroups, such as those of a specific age, or the severity of a person's symptoms. This makes it difficult to assess whether this calculation is accurate, or even reasonable.
So basically someone pulled a number out of their arse and then multiplied it by 17...
The BBC article quotes two specialists.
The problem is not overdiagnosis anyway, according to the article. It is rushed diagnosis or disgnosis based on incomplete testing. More testing would cost more money of course. The two specialists complain about trivialisation of asthma, and that people forget it is a potentially fatal disease. This is not actually caused by overdiagnosis but by failure to communicate to patients how important it is to monitor asthma and to return for frequent checkups. Frequent checkups and more monitoring means more cost of course. It is cheaper for doctors to prescribe the medications and instruct patients and parents on how to take them.
A doctor from NICE, Mark Baker, points out that "Accurate diagnosis of asthma has been a significant problem which means that people may be wrongly diagnosed or cases might be missed in others." It swings both ways.
Again quoting from the BBC article linked, Asthma UK's Dr Samantha Walker says: "It is astonishing in the 21st century that there isn't a test your child can take to tell if they definitely have asthma.
"Asthma isn't one condition but many, with different causes and triggered by different things at different ages. Asthma symptoms also change throughout someone's life or even week-by-week and day-by-day.
"This complexity means that it is both over and under-diagnosed, in children and in adults, so people don't get the care they need to manage their asthma effectively.
"As a result, a child is admitted to hospital every 20 minutes because of an asthma attack and asthma attacks still kill the equivalent of a classroom of children every year in the UK."
......So I think we may console ourselves that the entire business of diagnosis is screwed up thanks to successive governments financial starvation of the NHS, and that for every person wrongly told they have asthma there is probably someone else wrongly told they don't have it.