I've written a lot of protest letters and quite a few complaints, but I'm a bit wary in this case because I've got to keep them on side, they're the only surgery I can go to and they do prescribe testing strips
I'll think about it though, and see what they have to say tomorrow - but if they don't call me back by the time I've got my gander up they'll be getting a letter!
To be honest, I'm certain you could make your point, quite elegantly and eloquently, leaving nobody unclear about how you feel about things, without insult or name calling.
I would certainly do this in writing. That way, you have time to compose and be composed. You can read and reread what you write and check it both means what you want to say, and says what you mean. I suggest a tactic of feedback. Tell the Practise Manager you would like to point out a set of circumstances which appear to have led to an unforeseen and mutually unwelcome outcome. Describe the reason for bloods, the taking of them, and the follow up actions. (Expect results/call for results, or whatever.)
Then describe what happened - I.e you called, having waited for feedback to be told the tests had not been completed due to samples spoiling, as a result of an apparent procedural error (not refrigerating samples).
At that point, I might be inclined to offer Alan olive branch stating, human error can occur, and samples may be spoiled, but you are disappointed nobody contacted you to ask the blood drawn again. Point out the wasted time, and delays and explain in this case, it has led to frustration, and potentially a delay in a diagnostic decision which is important to you, albeit not life threatening. That it is not the latter is good fortune, rather than actions taken, it seems.
If you take that approached, stating how you feel, it is unchallengeable, provided it is factually correct. They cannot say you don't feel x, y or z. They can state it is unreasonable, but cannot say it doesn't happen.
I would then state you feel the Practise Manager needs this feedback, to ensure the chances of this recurring are minimised; for obvious reasons, and ask her what steps will be taken to ensure this is the case.
In reality, I think you should be thanked for your feedback and told an investigation needs to take place to understand exactly what transpired, and how your situation could develop, and invite you to have bloods retaken (if they haven't already been done, by then). On that basis, I bet there won't be any issues with the second samples.
Good luck with it all!