HERPES

Why Are Blood Tests for Syphilis and Herpes not conclusive?

Dear Dr. Tom:

I went to a doctor about three weeks after I noticed a red sore near the head of my penis (between the head and the top of the shaft). He said it was probably just from friction from masturbation, and not a STD. However, he said it is hard to tell since I didn’t go to see him when the irritation first developed. As a precaution, he took a blood test which he said he would have tested for syphilis and herpes. The result for syphilis was negative and the test for herpes has not come back yet. He said that I need to get another blood test in approximately two weeks to confirm the results for the syphilis test. Why is this? Also, he said that the blood test for both STDs are not conclusive. Why is this? I asked him, but didn’t really understand his answer. Can you help me to understand both the inconclusive nature of the blood tests, as well as why it is necessary to have a comparison test for syphilis? I would really appreciate it if you could clear up these issues for me. I am very worried and anxious about my condition. Thank you.

Worried and scared.

---

Dr. Tom’s Response:

Dear Worried and Scared:

Serologic tests for syphilis (STS) fall into two types: presumptive and confirmatory. Presumptive tests are intended to give a rapid answer (high sensitivity) and tend to be somewhat less specific. The confirmatory tests are also known as treponemal tests because they use an actual extract or fraction of the infectious treponeme as a test component. The treponemal procedures tend to be highly specific but have a lower level of sensitivity. Perhaps your doctor wants to be sure about a possible diagnosis of syphilis and is doing both types of tests. If he felt the sore resulted from friction rub caused by masturbation, he might have taken a skin culture in an effort to attempt to identify the causative agent. STS are based upon the ability of a medical laboratory to detect immune proteins in your blood serum (antibodies) that arise in response to presence of the infecting micro-organism. In all serologic procedures some false positives and some false negatives occur for a variety of reasons. This is why your doctor said that the blood tests were not conclusive. The physician attempts to make a decision based upon the best total information available, in your case a clinical exam and a complete STS battery. Thank your doctor for this, because positive STS results are reportable to the public health authorities under penalty of law; positive herpes serologic test results are not. In primary syphilis the initial sore disappears, leaving the infected person much relieved that it went away. Alas, however, it will return in a different form if no treatment is received. The reason for lawfully required reporting is to insure that persons who test with positive STS results see a physician and receive treatment. Untreated syphilis can have dire results. Nero, Caligula, and Bloody Mary Tudor were examples. Your anxiety is understandable, but syphilis is completely curable by antibiotic treatment, while herpes is not.

---