Today, I was able to meet with an acquaintance of mine who is a PhD researcher for Pfizer. She’s been doing vaccine research for the past three or four years (I don’t think she worked on Viagra years ago, but she did mention it was their biggest moneymaker until Lipitor came along). We spoke for over thirty minutes, wish I took some notes, so I’ll summarize what she said. She went into some serious detail regarding the techniques in question.
She uses both immunoassay and LC/MS in her work, and from the sound of it, daily. Overall, she was much higher on the immunoassay procedure. She said it was more reliable and repeatable. She said the LC/MS equipment was much more temper mental and more difficult to use, with the skill of the operator critical and results more likely to be impacted by user error.
I explained the issue with estradiol. She didn’t seem to grasp the problem, insisting that immunoassay was the way to go, unless, the level would be unperceivable by immunoassay, in which case LC/MS would be the method of choice.
I understand that the immunoassay can (or does) over state your true E2 levels, which is what surprised me with mine, since immunoassay was 21 ng/mL vs 23 ng/mL LC/MS.
She just shrugged when I asked about that, saying that if repeat tests were performed that the IA would more likely be the same while the LC/MS less likely. Essentially, according to her, unless you’re expecting levels below 15 there is no reason to use the LC/MS test.
My doctor maintains the immunoassay is fine and the 20-22 range is what we want to see for E2. If anyone comes back <15, he decreases their anastrozole dose, or, if test is still low, increases test dosage. But, he does rely on symptoms, especially if it’s higher.
Hope this helps. Regardless, next time I get blood work, I’m going to ask for both again. It’ll be interesting to see if they are consistent.