Why did one of my fingers turn blue?

Hello doctor,

I am a 27 year old woman. Two years ago, it happened for the first time that one of my fingers turned blue. A few seconds after that, it lost its color like it did not have oxygen and started to hurt. It comes in the winter, but nowadays, I have it on the other fingers on my hand and legs too. Even a slightly low temperature can cause this. I read about cryoglobulin and the symptoms look the same. I went to a doctor, but she told me her laboratories do not have tests to diagnose cryoglobulinemia. So, I would like to ask you, what examinations do you recommend to a patient with these symptoms and why? What else can be the reason for these conditions?