Chlamydia Positive via Blood Test

Hi Doctor,
On 4/20/09, I did a STD test (HB, RPR, HIV, Herpes I &II, Chlamydia) with my internal medicine doctor, who collected blood and urine sample from me. On 4/27/09, I got my result back and it showed Chlamydia positive based on my blood sample (urine was not used in testing for Chlamydia). He prescribed me with Doxycycline Hyclate 100mg for 7 days (twice daily) and on the same day I asked my recent past and current sex partners to get tested. I finished my medication on 5/4/09.
However, my most recent past and current sex partners with whom I had unprotected sex were all tested negative for Chlamydia. Here is the summary of my recent past sex history:
Name, Sexual relationship timeline, Comment
K, Oct 07 - Nov 08, unprotected sex
S, 12/27/08, protected sex (condom was used throughout)
K, 12/28/08, unprotected sex
L, 1/1/09, unprotected sex
V, Feb 09 to Apr 09, unprotected sex
K, L, and V all have Chlamydia negative via swab test done in late Apr 09.

On 5/10/09, I went back to the same doctor to do another blood test for Chlamydia, and I also went to a hospital to perform a swab test (a stick was inserted into my penis) just to make sure whether my first test was a false positive, I will get both results in a week.

Questions:

1. If I did have Chlamydia, since I have already finished my prescription on 5/4, would the swab test done on 5/10 be able to tell if I ever was indeed infected with Chlamydia? What conclusions can I draw if the swab test is negative?

2. Would it be possible for me to have Chlamydia but not infecting my sex partners?

3. Could my doctor be confused between Chlamydia pneumoniae and Chlamydia trachomatis (the former is not a STD I believe?) based on the blood test? I did have sore throat and cold/allergy-like symptoms in early Apr 09 (around 4/3-4/5)

4. Should I ask all my previous sex partners to do a STD test (prior to K)? If I indeed had Chlamydia I need to tell them asap to prevent serious health problems to them.

Thank you.

[Edward W Hook, MD]

Your doctor should be congratulated for being thorough and you are asking good questions.  Having heard of your situation in which your concerns, all began with a blood test which was positive for chlamydial antibodies, I suspect that your doctor is a victim of poor laboratory service.  The standard used as an indication for treatment for chlamydia is either a positive urine or swab test for the organism or a history of a sex partner who had positive urine or swab tests.  The blood tests for chlamydia should not even be offered as they can detect antibodies to Chlamydia pneumonia (i.e be falsely positive for Chlamydia pneumonia) and can remain positive for years after resolution of a Chlamydia trachomatis infection.  They should not be used to guide therapy for chlamydia infection as they can be positive for antibodies generated long ago and since resolved.  Thus, in answer to your questions:

1.  You can trust that swab test.
2.  If you had genital chlamydial infection you had to get it from someone and probably would have given it to one of your sex partners, particularly those with whom you had unprotected sex).  My guess is that you do not have chlamydia and did not at the time of the positive blood test.
3.  Yes, your blood test could have been false positive.
4.  No there is no need to go back further.

Hope this helps.  EWH

[hubsc]

I sincerely appreciate your helpful opinions.

Yes, you are right, my internal medicine doctor drew his conclusion based on the abnormal level of chlamydial antibodies observed in my blood sample.

Did you mean to say "it can remain positive for years after resolution of a Chlamydia pneumonia [instead of trachomatis]"?

And, sorry, I just want to make sure that I am perfectly clear on (1): Since I have already finished the treatment (on 5/4/09),  if I did have Chlamydia trachomatis infection at the time my first blood test was done (4/20/09), could my swab test that was done on 5/10/09 (~5-6 days after my last pill) still be able to show a positive result? (How long after treatment can a swab test pick up a Chlamydia trachomatis infection?) i.e. if my swab test shows negative, can I conclude that I actually have NEVER been infected with Chlamydia trachomatis and my first blood test (4/20/09) was false positive for Chlamydia trachomatis infection?

Thank you very much for your time and attention.

[Edward W Hook, MD]

The blood test can become positve because of either C. trachomatis or C. pneumonia infections.  Either infection could explain your result.

Following treatment a negative test is proof that you do not have chlamydia at that time.  Whether you had it before or not in the past cannot be determined based on tests after therapy.  Your positive blood test could reflect wither a false positv etest result or a prior chlamydial infection of some type.  EWH