I want to post this information again, as it seems highly relevant to many of us. "The time from detection of AMA to development of PBC is about 6 years (range 1-19 years). Only about 10% of patients who are AMA seropositive, but lack clinical features of PBC, subsequently develop PBC."
This means that if you just had a routine liver test that showed an AMA elevation, but you have no other abnormal results and no symptoms, you have an average of six years until you develop PBC, and there is a 90% chance you will not develop it at all. This is why, in the US, AMA alone is not diagnostic of PBC.
I've given numerical examples before; here is a new one for 2017. We know that at least 0.5% of the population is AMA-positive, whereas the prevalence of PBC is, at most, 1 in 3000. We also know that the gender ratio is at least 9:1 female: male for PBC, but is approximately equal (1:1) for AMA.
Suppose there are 30,000 men and 30,000 women who are randomly tested. 150 (0.5%) of each will have AMA. In addition, 20 people (1 in 3000) will have PBC. In order for the gender ratio to be 9:1, this means that 18 of the people will be women and 2 will be men.
It follows that, for men, the probability of having or developing PBC, given AMA positivity but no other indicators, is 2/150, which is only 1.5%. This may not be surprising, given that the disease is fairly rare in men.
But what may surprise you is that, for women, it's also low. It's 9 times that amount. In this example, that's 18/150, or 12%.
So if you test a bunch of AMA-positive but otherwise normal people for PBC, and most of them are women, you will get a number between 1.5% and 12%, but closer to 12%. No surprise, then, that the NIH paper cited above comes up with 10%.
Any statement that AMA alone is "virtually diagnostic" of PBC, even in the absence of any other features, should be questioned and, if possible, reconciled with these statistics. If you have AMA but no other indicators, be sure to see a specialist, get checked every six months, etc. but there is no reason to freak out.
And if you do have PBC, as many on the site have noted, you will likely still lead a normal life, particularly if it is detected early and treated with Urso.
I hope that many of you find this information helpful.