Choosing the right body site for STI testing sample

Testing for STIs today is easier than ever before. Science has made it possible to get tested from the comfort of your home, with an equal precision and accuracy as analysis performed in the doctor's office, leaving little space for excuses when it comes to avoiding STI testing. If doctor's visits are part of your regular routine, it is important to know that most of doctors do not conduct routinely STI testing, but it is needed to make a specific request for the analysis.

The testing procedure depends on the ordered test. The decision on which test would be needed for you is based on visible or suspected symptoms, or possible risks to which you have been exposed to. After choosing the wanted test, it is crucial to choose appropriate type of sample. Possible forms of samples are:

  • blood
  • urine
  • swabs (oral, cervical, vaginal, anal, penile)


In different tests, different sample types are used. For instance, for HIV test blood sample is used, while for HPV appropriate swab sample is needed. Also, not every sample type is approapriate for every test. For example, blood sample for testing HPV would not be efficient way in determining presence of infection.

Need2Know tests are based on the detection of pathogen's DNA within the sample. Unlike the antibodies which are present systematically, pathogen will be present on the site of the infection. Therefore, it is important to understand that the choice of body site for sampling depends on the site of sexual contact because of which you doubt on STI. During sexual contact with an infected person, site of sexual contact is the primary infection site, where pathogen will be located. For instance, it is justified to suspect of oral infection if you had oral sex with an infected person, and in case you decide to get tested, it will be needed to provide an oral swab for the analysis. In this case, if you send a cervical, penile or anal swab instead, there is a possibility of receiving negative test results, although oral swab would show positive. If one type of sample comes out negative, it does not imply that other body site samples would also come out as negative!

Also, it is important to understand that getting tested on same pathogen but from different body site samples is not treated as a single test. In case you had vaginal and oral sex, and you send vaginal and oral swab, these swabs are analyzed separately, as two separate tests. Why? Generally, it is possible to analyze those two samples together as a single test, but in case of positive results it would not be possible to recognize if there is an ongoing oral or vaginal infection, or both body sites are infected.


~STI testing revision~

  • Sample type depends on the site of the sexual contact. Experiencing only oral seks with an infected person most probably implies oral infection, and for its confirmation an oral swab would be needed. Providing a genital swab in this case would not enable identification of an oral infection.
  • Negative results from one sample type do not mean that other body sites are not infected as well! Risk of possible infection depends on types of previously experienced sexual contacts.
  • Different types of samples for same pathogen are analyzed as separate tests. Otherwise, it would not be possible to determine real site of infection.