The normal range: it is not normal and it is not a range

I often post the text and link below on HealthUnlocked because it is one of the best papers about reference intervals - normal ranges.

Because it comes from the medical world, written by medics and published in the British Medical Journal, it should be convincing to healthcare professionals.

It is also written in a way that is reasonably accessible to many patients, at least with a bit of careful reading.

The normal range: it is not normal and it is not a range

Abstract

The NHS ’Choose Wisely’ campaign places greater emphasis on the clinician-patient dialogue. Patients are often in receipt of their laboratory data and want to know whether they are normal. But what is meant by normal? Comparator data, to a measured value, are colloquially known as the ’normal range’. It is often assumed that a result outside this limit signals disease and a result within health. However, this range is correctly termed the ’reference interval’. The clinical risk from a measured value is continuous, not binary. The reference interval provides a point of reference against which to interpret an individual’s results—rather than defining normality itself. This article discusses the theory of normality—and describes that it is relative and situational. The concept of normality being not an absolute state influenced the development of the reference interval. We conclude with suggestions to optimise the use and interpretation of the reference interval, thereby facilitating greater patient understanding

►Health is a relative and not an absolute state.
►The reference interval acts as a comparator for the patient’s blood result. It is not the arbiter of whether disease is present or not.
►Natural fluctuations in a blood result can occur.
►Comparison of a result against the reference interval should be informed by the clinical suspicion made beforehand.

The full paper is freely accessible here: 

https://academic.oup.com/pmj/article/94/1117/613/6959235?searchresult=1

There is also a reasonable video which might help:

There is also a very good talk on thyroid testing by David Halsall

 

To link from HealthUnlocked, copy the entire red text below and paste into a post or reply.

This is a link to a very good article in the British Medical Journal discussing what the 'normal range' really is. Very readable.

[i][b]The normal range: it is not normal and it is not a range[/b][/i]

https://helvella.blogspot.com/p/the-normal-range-it-is-not-normal-and.html

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