It's Hard to Stay Positive: Lyme Tests

Remember how I was encouraging us to cut the CDC some slack? Well today, I'm going to reel some of it back in.

We're looking now at question #7 about testing negatives and positives. Lot's of folks in the lyme community feel frustrated by the lack of good testing. On the other hand, the phrase "false positives" seems to come up whenever we talk lab results, and I think it is worth taking a little time to talk about that.

Here's what the CDC says about false positives: "If a patient has not been in an area where Lyme disease is common or their symptoms are atypical, positive results are more likely (emphasis mine) to be false positives. Similarly, if a patient is tested numerous times and only rarely tests positive, it is likely that the positive result is a false positive."  

More likely. Not "potentially" or "under some rare circumstances possibly" nor a general statement on being a careful medical practitioner being wise. No, they seem to actually be saying, "Feel free to blow it off if you don't think it could be right."

Just when I was starting to like them more.

There are multiple things in these two statements that are highly questionable. I am certainly willing to grant that it is easier to get lyme in some places than others. However, in this case, the idea that it can't happen in certain areas has created a false impression that it really isn't happening in those areas. (And thus, a low diagnosis rate.)

If doctors in supposedly low risk states won't diagnose the same presentation that a doctor in a high risk state will, then we have biases running our diagnostic standards rather than sensibility. This is a circular thing: if you don't believe it can happen here, then by not diagnosing it, you reinforce the statistics that say it can't happen here.

(Now it is also true that it is incredibly difficult for a conscientious doctor to keep up with all the emerging new information out there, and it is understandable that not everyone recognizes the symptoms profile with equal skill. More experience diagnosing any illness will lead to better skill at it in the long run.)

Here's a few different maps of risk level in different states. Let's start with the CDC's own map, Reported Lyme Disease Cases by State, 2000-2010

Remember that the real number is probably 10-13X the number of CDC confirmed cases, and those numbers are going up each year, not leveling off or dropping. The next map is from 2000, from the American Lyme Disease Foundation. The importance of this second map is how geographically spread out cases were 12 years ago.

Remember that birds, reptiles and mammals (including people) don't stay in one place. The more mobile we are, the more we contribute to things spreading.

And finally, here's a map describing distribution among man's best friend, with numbers from 2007. (Anyone else notice that dogs seem to being studied more than people? I love dogs... and yet something about this bugs.) The important thing here is that the bug that causes lyme in dogs is the same one that causes lyme in people; if dogs are getting diagnosed at higher rates in some of these states, why aren't humans?

When I look at these maps, the big take away I get (no matter what the source, or which big mammal we are talking about) is that lyme is all over the continental US. While one map each show nothing in Mississippi or the Upper Peninsula of Michigan, there isn't a region without lyme anywhere on here. (And gosh, sorry, Wisconsin. You're really taking the hit for us midwesterners, aren't you?)

So when the CDC says that a test might be considered a false positive because lyme isn't common in that area, I'd like to know their definition of common. I'd also like to know why they think it is OK to ignore those "uncommon" cases; just because everyone in the neighborhood doesn't have it doesn't mean you don't have it, ya know? Do we ignore rare cancers because they are rare, even when all the other evidence points to them?

The second thing in their statement is about "atypical symptoms". We'll talk more about this soon, but the bottom line is, there is no universal symptom for lyme, and people fit pretty different profiles. Some are mainly neurological, some mainly "fibromyalgia" type symptoms (tired and achy) some have lost their sex drives and/or gone into early perimenopause.

Which profile should we consider to be the "typical" one? (And please don't tell me it's that rash. See two blogs ago.)

Finally, the CDC doesn't like inconsistent test results. (Neither do I actually; where we differ is on what to do with them.) And that brings us to today's survey question about testing. I asked folks to share with us a quick look at their testing history and here's how it shakes out:

So here we have a population of people who have lyme. For 37%, the testing worked on the first go. However, a larger number of people got a negative before we got a positive. Some of this has to do with what type of testing we did. (In my case, I tested negative, crossed lyme off my potential illnesses list and muddled through for months before a friend hipped me to the fact that there is different testing out there and got someone to send my blood to Igenex, which yielded a positive. Thank you Mary Lou Singleton!)

However, a lot of it also has to do with what kind of shape your immune system is in. And according to Dr. James Schaller, bartonella in particular is very good at depressing the immune system in such a way that it causes lyme tests to be negative. And a lot of us have bart (as it is unaffectionately known to those of us who are most intimate with it.) Plus, tests are often reading your immune response in some way, and the sicker you are, the less likely you are to have a predictable, "normal" immune response.

Inconsistent testing can thus have as much to do with what is ascendant in your system at the time you got tested as what is actually going on in the tick soup of our bodies, or it can have more to do with the general state of your immune system, than it does whether or not you actually have lyme.

And there are any number of other factors than can depress the immune system (including a long term undetected lyme infection itself. See the blog from July 3 for a sense of what our lag times between becoming infected and being diagnosed can be.)

Further, if you have just gotten infected, you might not show up as a positive either because your immune system is not yet responding. In some ways, these are the most tragic false negatives to ignore, because lyme is much easier to deal with if caught within those first couple weeks, when it is not left to linger and dig in.

Thus, the very common occurrence of negatives tests... and my reasons why I think the CDC's apparent preference to discount the positive test as a fluke is probably exactly the opposite of what we need doctors to be listening to. Notice nothing in the CDC's statement gives us any reason to think that the pathogens were incorrectly identified.

Now that would be a real reason to consider a test to be a false positive, but it isn't what they are arguing. But in light of a clinical presentation consistent with lyme symptoms, any positive test (save one from a truly incompetent lab... which you shouldn't probably be using anyway) should be seen as building the case for lyme.

Somewhere in this diagnostic equation mess, there ought to be some space for trusting ourselves. When we know something is wrong, and the explanations we are being given don't make sense to us and when science (and the agencies meant to serve it) fails us, we need to trust our own bodies and what we know for ourselves.

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Bonus for those who are joining in late in their reading of my blog: a link from the Canadian Lyme Disease Foundation provides a host of reasons why someone with lyme might test negative.