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What Is The Percentage Of False Positive Results For Lyme Disease?
Question: Hi there,
Around October of 2013, I started experience (still) unexplained muscle twitches and began seeing a doctor about that as well as other concerns (blood pressure and general health, mostly). Recently, after discussing various options, I had a blood test for Lyme disease.
Today I got the results, and the test (which I'm told is an initial test...not conclusive) was positive and I was told that I'd need a more specific test to confirm whether or not it is in fact Lyme disease (which I will get as soon as possible, hopefully this week).
I have a few questions and would appreciate some help.
1.) How specific is this initial test? If possible to answer, what is the percentage of false positives and how likely is it I actually do have Lyme Disease?
2.) I'm told if it is Lyme, standard treatment is a course of antibiotics, though I'm aware treatment is considered most successful if early. Given the data, my assumption is exposure (perhaps when mowing in the summer of 2013) was some 18+ months ago. Is this still considered early enough, or is it likely my prognosis is more complicated and standard antibiotics may not treat it?
3.) My twitching was definitely most apparent near the end of 2013 and first half of 2014. It has abated quite a bit since then - I still get the occasional minor twitch, but it is much better than it was. Is it possible my immune system cleared Lyme (if it was Lyme) on its own, or is this something that cannot be cleared without antibiotics?
4.) Current CDC guidelines do not seem to indicate Lyme can be spread through sexual contact. (See http://www.cdc.gov/lyme/faq/). However, there were some recent (2014) articles and a study (though I don't believe peer reviewed) questioning whether it could be sexually transmitted. Some sources say the study has faults and to trust the CDC guidelines, while others think sexual transmission could be possible and more study is necessary. As a sexually active XXXXXXX male, should I be concerned about this/notify potential partners, or is it something that's definitely not a worry?
Thank you much for your time/expertise.
Around October of 2013, I started experience (still) unexplained muscle twitches and began seeing a doctor about that as well as other concerns (blood pressure and general health, mostly). Recently, after discussing various options, I had a blood test for Lyme disease.
Today I got the results, and the test (which I'm told is an initial test...not conclusive) was positive and I was told that I'd need a more specific test to confirm whether or not it is in fact Lyme disease (which I will get as soon as possible, hopefully this week).
I have a few questions and would appreciate some help.
1.) How specific is this initial test? If possible to answer, what is the percentage of false positives and how likely is it I actually do have Lyme Disease?
2.) I'm told if it is Lyme, standard treatment is a course of antibiotics, though I'm aware treatment is considered most successful if early. Given the data, my assumption is exposure (perhaps when mowing in the summer of 2013) was some 18+ months ago. Is this still considered early enough, or is it likely my prognosis is more complicated and standard antibiotics may not treat it?
3.) My twitching was definitely most apparent near the end of 2013 and first half of 2014. It has abated quite a bit since then - I still get the occasional minor twitch, but it is much better than it was. Is it possible my immune system cleared Lyme (if it was Lyme) on its own, or is this something that cannot be cleared without antibiotics?
4.) Current CDC guidelines do not seem to indicate Lyme can be spread through sexual contact. (See http://www.cdc.gov/lyme/faq/). However, there were some recent (2014) articles and a study (though I don't believe peer reviewed) questioning whether it could be sexually transmitted. Some sources say the study has faults and to trust the CDC guidelines, while others think sexual transmission could be possible and more study is necessary. As a sexually active XXXXXXX male, should I be concerned about this/notify potential partners, or is it something that's definitely not a worry?
Thank you much for your time/expertise.
Brief Answer:
Not very specific, that's why there is a second test
Detailed Answer:
Hello,
(1) let me provide some facts about diagnosis: the two-step diagnostic strategy is used to prevent false positives because the initial test is not specific enough to guaranty that the patient does have the infection. The second test is less sensitive (and that's why it's not used as a first test) but more specific. It's sensitivity may be different depending on the Borrelia burgdorferi strain.
In cases like yours (with a duration of more than 8 weeks) an IgM positive test can be considered false positive (the second test is still needed). There is a serologic study which has shown a 50% chance of positive antibodies to the serum without disease. So perhaps this is an indirect answer to your question, although I cannot provide a clear percentage because this is not as simple as I put it.
A second generation ELISA (C6 peptide ELISA) provides more credible results (IgG antibody) but this is not specific enough either. The Western Blot (the second test) is needed anyway.
(2) If symptoms are present (and attributed to Lyme disease) then the treatment is the same. In a case like yours I would have chosen doxycycline for 21 days.
(3) The immune system may indeed compromise Borrelia burgdorferi without treatment but it may also remain active for years perhaps with exacerbations.
(4) According to current knowledge, sexual transmission is not likely. This is considered a tick-bite disease.
I hope you find my answers helpful!
If you'd like me to clarify any part of my answers, please use your follow-up questions. I'll be glad to help more, if I can!
Kind Regards!
Not very specific, that's why there is a second test
Detailed Answer:
Hello,
(1) let me provide some facts about diagnosis: the two-step diagnostic strategy is used to prevent false positives because the initial test is not specific enough to guaranty that the patient does have the infection. The second test is less sensitive (and that's why it's not used as a first test) but more specific. It's sensitivity may be different depending on the Borrelia burgdorferi strain.
In cases like yours (with a duration of more than 8 weeks) an IgM positive test can be considered false positive (the second test is still needed). There is a serologic study which has shown a 50% chance of positive antibodies to the serum without disease. So perhaps this is an indirect answer to your question, although I cannot provide a clear percentage because this is not as simple as I put it.
A second generation ELISA (C6 peptide ELISA) provides more credible results (IgG antibody) but this is not specific enough either. The Western Blot (the second test) is needed anyway.
(2) If symptoms are present (and attributed to Lyme disease) then the treatment is the same. In a case like yours I would have chosen doxycycline for 21 days.
(3) The immune system may indeed compromise Borrelia burgdorferi without treatment but it may also remain active for years perhaps with exacerbations.
(4) According to current knowledge, sexual transmission is not likely. This is considered a tick-bite disease.
I hope you find my answers helpful!
If you'd like me to clarify any part of my answers, please use your follow-up questions. I'll be glad to help more, if I can!
Kind Regards!
Above answer was peer-reviewed by :
Dr. Chakravarthy Mazumdar
Thank you so much for your clear, detailed, and informative response! Just a few clarifications to make sure I understand all your points:
1.) So basically, there's a good possibility this is just a false positive (about as likely as I actually have Lyme), so there's no point being over-concerned until the second test comes back?
2.) Good to know re the treatment being the same. Is prognosis and chance of clearing it fairly good, even after 18+ months of being infected (if it is Lyme), with the single course of antibiotics?
3.) Good to know it's possible my immune system took care of it (though from what I understand, there's likely no way to verify that?).
4.) Based on current knowledge and evidence, from what you're saying, then there is no ethical need (or even suggestion) to disclose/discuss or change sexual
behavior with partners, correct?
[Since initially asking, I have found some interesting articles, some written by doctors, criticizing that non-peer-reviewed study and stating reasons why sexual transmission is unlikely; that study just worried me a bit.]
Thank you very much again.
1.) So basically, there's a good possibility this is just a false positive (about as likely as I actually have Lyme), so there's no point being over-concerned until the second test comes back?
2.) Good to know re the treatment being the same. Is prognosis and chance of clearing it fairly good, even after 18+ months of being infected (if it is Lyme), with the single course of antibiotics?
3.) Good to know it's possible my immune system took care of it (though from what I understand, there's likely no way to verify that?).
4.) Based on current knowledge and evidence, from what you're saying, then there is no ethical need (or even suggestion) to disclose/discuss or change sexual
behavior with partners, correct?
[Since initially asking, I have found some interesting articles, some written by doctors, criticizing that non-peer-reviewed study and stating reasons why sexual transmission is unlikely; that study just worried me a bit.]
Thank you very much again.
Brief Answer:
Yes to most questions
Detailed Answer:
Hi,
(1) a positive IgM (ELISA) and a negative IgG (Western Blot) means no disease.
(2) Depending on disease spread, a single course of antibiotics can be sufficient, perhaps for an increased duration of treatment. Sometimes intravenous antibiotics are needed.
Please note that your symptoms are not conclusive and unless a conclusive laboratory result is obtained, no treatment would be recommended.
(3) It's not easy to verify successful treatment because the antibodies may still be present after the eradication of Borrelia (for many months). Lack of symptoms should be sufficient as an indication of success. Other methods of detection have similar problems.
(4) Since no sexual transmission has been reported, no unnecessary worries are justified.
I hope that I've made it more clear. If you still have questions, please contact me again.
Kind Regards!
Yes to most questions
Detailed Answer:
Hi,
(1) a positive IgM (ELISA) and a negative IgG (Western Blot) means no disease.
(2) Depending on disease spread, a single course of antibiotics can be sufficient, perhaps for an increased duration of treatment. Sometimes intravenous antibiotics are needed.
Please note that your symptoms are not conclusive and unless a conclusive laboratory result is obtained, no treatment would be recommended.
(3) It's not easy to verify successful treatment because the antibodies may still be present after the eradication of Borrelia (for many months). Lack of symptoms should be sufficient as an indication of success. Other methods of detection have similar problems.
(4) Since no sexual transmission has been reported, no unnecessary worries are justified.
I hope that I've made it more clear. If you still have questions, please contact me again.
Kind Regards!
Above answer was peer-reviewed by :
Dr. Chakravarthy Mazumdar
Excellent! Thanks for all the clarifications!
One last question - assuming the second test came back negative (no Lyme Disease), would the positive for the first test mean something else besides Lyme necessarily? Or can that first test just be positive even if nothing's wrong?
Thanks again - that should complete my questions!
One last question - assuming the second test came back negative (no Lyme Disease), would the positive for the first test mean something else besides Lyme necessarily? Or can that first test just be positive even if nothing's wrong?
Thanks again - that should complete my questions!
Brief Answer:
It could
Detailed Answer:
Hello,
there is cross-reactivity between antibodies against different diseases and the test antigens (like with Syphilis, HIV, Epstein-Barr virus etc). Sometimes non-infectious factors may cause this cross-reactivity. This is obvious because this is the cause of the low specificity of the ELISA test.
Whether you'll need further investigation depends on symptoms. Lab tests should not be the sole determinants of medical decisions.
Kind Regards!
It could
Detailed Answer:
Hello,
there is cross-reactivity between antibodies against different diseases and the test antigens (like with Syphilis, HIV, Epstein-Barr virus etc). Sometimes non-infectious factors may cause this cross-reactivity. This is obvious because this is the cause of the low specificity of the ELISA test.
Whether you'll need further investigation depends on symptoms. Lab tests should not be the sole determinants of medical decisions.
Kind Regards!
Note: For more detailed guidance, please consult an Internal Medicine Specialist, with your latest reports. Click here..
Above answer was peer-reviewed by :
Dr. Chakravarthy Mazumdar
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