I saw an asthmatic woman in A+E today, all her blood tests were in the 'normal' range, does that mean she's well?
No, she was very unwell. However the test results would either be normal in someone regardless of the severity of their asthma, or would be expected to be 'abnormal' in someone with mild asthma, and 'normal' in someone with severe asthma. The ability to interpret those test results, and take a history and examine the patient is important.
Similarly, we used the latest evidence-based guidelines to assess the patient's asthma severity, and based on several objective criteria (breathing rate, oxygenation of blood, peak flow, etc) the guidelines determined she had moderate-severe asthma
However we called the ICU doctors to see her. The ICU consultant, with many decades of experience managing acutely unwell asthmatics, simply looked at the patient for two minutes, observing how her chest moved during breathing, and the sounds and respiratory effort she was making, and decided to take her to ICU. This was a good decision as she ended up deteriorating and requiring very aggressive treatment. Whilst guidelines can make a suggestion based on the interpretation of some objective data points, the ability to assess a patient as a whole, based on history and examination, is still an important skill, and one which it is hard to automate
The test results list the 95% confidence interval range for the population the sample they used to calibrate the test is theoretically representative of. That's not the same thing as normal.
Tests are usually done for a clinical purpose, not just to find out what your result is. What do the numbers mean to you?
Many straightforward tests people can do and interpret themselves, like people with diabetes on insulin (measuring BSL). They're not all so straightforward.
