Health – Is it normal?

When talking about blood tests the “normal range” generally means the results from the middle 95 percent of the population. That is, the 2.5 percent at either end of the scale are “abnormal” by definition.
It’s easy to see that if we do 20 tests for a patient there is a high statistical chance that one of them will be abnormal, but that doesn’t mean there is anything wrong with you. For instance, the normal range for the number of white cells in the blood is from 4.0 to 11.0.  So what does it mean if your white cell count is 3.9?  Probably nothing, but it depends on the clinical context. In that case a better question to ask might be whether the result is “significant”. This issue is becoming more important as patient portals allow access to notes, engendering some concern if the results are not explained. Beware the uninterpreted test!

Then what about blood pressure? When we say blood pressure is “normal”, what we mean is that it is at a level where health complications are minimised. Every now and again authorities review the evidence and move the goal posts, so the blood pressure that was acceptable last year might not be now. And, once again, context comes into play, with much lower targets being set for patients with diabetes and heart disease. The same applies to cholesterol results that might be okay until you have a heart attack and then we prescribe statins. So a better word for ‘normal’ in this situation might be “desirable”.

And some conditions are purely a matter of definition. For instance, the test for diabetes is called an HbA1c. Below 40 is “normal”, 40-49 is pre-diabetic but as soon as you hit 50 you are a diabetic and we throw the book at you. It’s a bit like the road rules: there is not much difference between 99 kph and 101 kph but technically the latter is speeding.

The situation is even more complicated when we are talking about behaviour, where normality is often defined by culture and fashion, rather than science. So, being normal might be harder than you think. You could need a highly trained health professional to know whether you have achieved it!