This is a general question, but I know I'll get good answers here, so I hope it's okay to ask. Is it unusual in a clinical setting to do testing unmedicated and then medicated? I'm thinking that it's not unusual if the circumstances justify it, e.g. you need to show that the medication has done something, or you need the results to support a particular diagnosis.
I'm not sure what the answer would be generally, but I haven't come across it in the UK. I've been given numerous medicines speculatively, but in most cases it was pretty clear whether or not they helped. That seemed to be enough to decide whether or not to continue—measuring benefits or outcomes properly often takes quite a long time, which is hard on the patient when it's an acute problem or the disease process is causing damage that can't be reversed. The meds involved weren't the high risk type that need very close monitoring, though.
Depends on the medication. One example of this is the diagnostic test for adrenal function. If you are taking steroids it may make the interpretation difficult due to its effect on the feedback loop for cortisol (ACTH). Also women taking oestrogen. More explanation available in this link: https://www.gloshospitals.nhs.uk/ou...acthen test is,(also known as tetracosactrin).
It is absolutely routine in specific circumstances. For hypertension you measure BP without medication and then with. In RA you measure CRP without medication and then with. In diabetes you measure blood sugar without medication and then with. In infection you do cultures without drugs and then to show it has gone - at least for viruses and TB. You do it all the time when you have a measure that gives objective evidence that your medication is doing the sort of job you want it to do physiologically. It is central to the outcome measures we use for trials in RA. It is also used, as @hibiscuswahine says for certain diagnostic test for endocrine disorders and other things.
Yes, another endocrine disorder is hypothyroidism where you test your thyroid hormones for diagnosis. Then you get medication and you have to keep doing the tests to see if it works or you need to increase or decrease the dose, especially as time passes (first every 3 months, if it's good then after 6 months, then after only annually).
There are some antivirals such as Valcyte that need regular testing to monitor your WBC, RBC and platelets. Some patients have to be taken off the drug entirely.
Thanks, folks, for the helpful replies. I have a horrible feeling that my daughter may need re-testing and that her specialist is going to refuse to order it. I just wanted to hear from some sensible people that re-testing is useful and even required in certain circumstances. (Unfortunately it is not something she can order herself, like a blood test.) I will post more about what ensues after she has the unmedicated test, which should be at the end of the month if the washout goes to plan. Thanks again.
