New Year, Same Message

Hi Everyone,

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)[35]. Only about 10% of patients who are AMA seropositive, but lack clinical features of PBC, subsequently develop PBC."

ncbi.nlm.nih.gov/pmc/articl...

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.

8 Replies

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  • I LOVE THIS!! Thanks!

  • Superb, as always Kevin.

    Thanks for all your informed, eloquent and sane posts.

    Take care and have a brilliant 2017!

    Carole (aka Gritty)

  • Thank you for posting!

  • Hi Kevin,

    I just have one question, when you talk about the AMAs, are you referring to general AMAs, or AMA M2? I find it a bit confusing when I read that having an AMA positive result is indicative of having PBC, when in fact that is not the case, as just having an AMA positive test can also indicate the presence of other conditions, as stated on the Mayo Clinic webpage:

    "Antimitochondrial antibodies (AMAs) are detectable by indirect immunofluorescence in >90% of patients with primary biliary cirrhosis (PBC), but this method also detects AMAs of differing specificities in other diseases."

    The link below explains the difference between AMA and AMA M2:

    mayomedicallaboratories.com...

  • Some conflicting info out there for sure, Mayo Clinic also has this on there PBC page "Blood tests to check for signs of autoimmune disease. An analysis of your blood may reveal anti-mitochondrial antibodies (AMAs). These antibodies almost never occur in people who don't have the disease, even if they have other liver disorders. Therefore, a positive AMA test is considered a very reliable indicator of the disease. However, a small percentage of people with primary biliary cirrhosis don't have AMAs." What are supposed to hang your hat on? I honestly don't think they know for sure, according to my Dr. there haven't been enough studies done. It'll be a good question to ask the Hepa when I see him the 25th. Luckily, I did finally get a Dr. to test my overall AMA, and it was negative after having tested + for AMA M2, so I'll take it as a good sign.

  • Thanks to everyone for their likes, messages, and kind words.

    Dianne, this is an excellent point and an important distinction, which has been raised before. The article I cited is referring to AMA generally, not the M2 subtype. However, the vast majority of AMA positivity is associated with the M2 subtype. Also, M2 is not the only subtype associated with PBC. The below passage, from Wikipedia, notes that M4, M8, and M9 are also associated with PBC:

    "Antibodies to these specific antigens have been associated with a number of conditions:[4] anti M2, M4, M8, and M9 are associated with primary bilary cirrhosis; M2 - autoimmune hepatitis; M1 - syphilis; M3 - drug-induced lupus erythematosus; M6 - drug-induced hepatitis; M7 - cardiomyopathy, myocarditis; M5 - systemic lupus erythematosus and undifferentiated collagenosis, autoimmune haemolytic anaemia."

    More importantly, general AMA is shown a more accurate and specific predictor of PBC than the M2 subtype alone: "AMA is a better and more comprehensive marker than AMA-M2."

    ncbi.nlm.nih.gov/pubmed/245...

    Even if this were not the case, the very strong correlation between AMA and the subtypes associated with PBC (M2, M4, M8, and M9) means that the numbers I've presented above are roughly accurate, even for those with the M2 subtype. There simply aren't enough people who are AMA-positive but negative for M2, M4, M8 and M9, to move the needle.

  • Helpful to know ? As I am still waiting for diagnosis as I had high AMA and only few symptoms that was a year ago now still having tests done

    Question is wouldnt doctors investigate WHY our AMA is even registereing at all before symptoms begin to show. To me anyway it makes sense to try and stop it as it takes a long time for it to Blossom and is brewing in our bodies. Our bodies are trying to tell them something is wrong by starting in the blood. I am far from any health professional but thats just my personal feeling.

    Happy new year everyone!!

  • Welchd: AMA occurs in 0.5% of the *healthy* population, so it's not necessarily the case that "our bodies are trying to tell them something is wrong. Also, the fact that PBC is so much more common in women than men, yet AMA rates are the same, suggests that AMA doesn't tell the whole story. It may be a (mostly) necessary, but not sufficient, condition for PBC to occur, with the other factors being (mostly) gender-specific.

    Gritty: To Dianne's point, I know that you're an anecdotal example. You've stated that you've been AMA-positive but PBC-negative for many years. Do you know whether your AMA is associated with one of the PBC-subtypes (M2, M4, M8, or M9)?

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