Written by Dr.Deyn Natthakhet Yaemim (Founding Director) on 6 June 2015, Last updated 18 July 2022

Polymerase Chain Reaction (PCR) for STI Detection and Testing

What's New

Polymerase chain reaction (PCR) analysis is a laboratory technique used to find small amounts of DNA (genetic material) in a sample. Among other applications, PCR can be used to detect multiple sexually transmitted infections (STIs). For example, a lab can find DNA in a urine sample that reveals gonorrhea or chlamydia.¹

PCR revolutionized the study of DNA and has been called one of the most important advances in molecular biology. It was first developed in the early 1980s by American biochemist Kary Mullis, who won the Nobel Prize in Chemistry in 1993.²

PCR can be performed on DNA from many different types of samples, including:

• Urine
• Swabs of cells and fluids
• Blood
• Cerebrospinal fluid
• Sputum
• Stool
• Semen

How Does PCR Work?

The small bits of DNA in a sample are usually inadequate for analysis. PCR allows scientists to make a bunch of copies of the material (called amplification) quickly and inexpensively, which gives them enough to analyze.2

Primers

The first step of the PCR process is to create what are called primers—short DNA sequences that can join up with the ends of the DNA sample you're trying to detect. They're the trick to finding, amplifying, and detecting a particular piece of DNA, which can then be used for things like:

• Identifying a pathogen
• Diagnosing genetic disorders
• Finding genes that influence antibiotic resistance
• Genome mapping

Separating the Strands

Once you have your primers, the next step in PCR is to heat the sample so that the double-stranded DNA separates into two single strands—this is called denaturation. Then the primers are combined with the sample DNA.

After this, a DNA polymerase (enzyme) is added and starts replicating the DNA where it meets up with the primer. The DNA then goes through the denaturating and replication procedure again and again.

Exponential Growth

With each cycle, the amount of the target DNA segment increases exponentially. In the first cycle, one copy becomes two. Then two copies become four, then become eight, etc.

Generally, it takes between 20 and 40 cycles to determine whether the target DNA is present. If so, by that time there's usually a sufficient sample for analysis, as well.

Automated Thermal Processing

All the steps of a polymerase chain reaction—denaturing the DNA, applying the primers, and elongating the DNA—happen at different temperatures. That means after the initial mixture is put together, the steps can be controlled through a process known as thermocycling.

Thermocycling means that the temperature is held at the necessary levels for just long enough for each step to take place. Thus, PCR is an efficient way of amplifying the amount of target DNA. In fact, it can be accomplished in a single test tube with little need for human intervention.

Types of STIs Detected by PCR

Bacterial STIs

Viral STIs

Parasitic STI

Types of STIs Detected by PCR at PULSE CLINIC Thailand

In people who has infection with symptom (symptomatic infection) and without symptoms (asymptomatic infections), DNA PCR TEST can detect;

• Chlamydia trachomatis (serovars A-K) which causes chlamydia
• Chlamydia trachomatis (serovars L1-L3) which causes LGV or Lymphogranuloma venereum
• Neisseria gonorrhoeae which causes Gonorrhea 
• Trichomonas vaginalis which causes Trichomoniasis
• Mycoplasma hominis 
• Mycoplasma genitalium (an emerging STI)
• Ureaplasma urealyticum (read more)
• Ureaplasma parvum (read more)
• Herpes Simplex Virus type I (read about Herpes Simplex Virus)
• Herpes Simplex Virus type II
• Treponema pallidum which causes syphilis
• Haemophilus ducreyi which causes chancroid
• Cytomegalovirus (CMV)
• Varicella-Zoster Virus (VZV)

WHICH BODY PART CAN I GET TESTED FOR ASYMPTOMATIC INFECTIONS USING DNA PCR TEST?

Let's think about how we use our part of body to give ourselves (and our partners) pleasure. 

THROAT SWAB

Imagine we kiss and suck and all the oral sex we use our mouth (and tongue and throat) the infections can be localized on your tonsil glands. 
So for this area we perform a swab, gently rubbing the swab (or small cotton bud) on the back of the throat, on the tonsils, and in any other area where there might be redness, inflammation or pus. Throat swab can detect 14 infections mentioned above. There are no risks or complications associated with a throat swab culture. The test may cause momentary gagging because the back of the throat is a sensitive area, but it shouldn’t be painful.

ANAL SWAB

Doesn't matter if you are a man, a girl or a transwoman, if you like it from the back or using your backdoor for some fun the infections from your partners (or toys, hands, or gloves when fisting) can localize on the surface of anal canal or rectal tissue surface. Don't be too embarrassed to discuss your anal sex and safe anal sex practices with your doctor (We've seen many holes before and you won't be the last). To collect the specimen, a small cotton swab (you wish it is bigger) is placed into the anal canal and the rectum. The swab is rotated gently, removed and put in a container to be sent to our lab. There may be pressure as the swab is inserted into the rectum. The test shouldn't cause you any pain, we are always gentle and handle with care.

VAGINAL SWAB

We're talking about woman and transwoman, vaginal canal can be a house to host STI party and a matter of fact, STIs amongst transwoman do not differ from the non-TG population unless there are other risks factors involved. To collect the specimen, a small cotton swab is placed into the vaginal canal. The swab is rotated gently, removed and put in a container to be sent to our lab. 

URINE PCR FOR 14 INFECTIONS

Urine testing for STIs is becoming increasingly available. These days, 14 STIs can be detected using urine testing. Urine PCR test is a lot more pleasant than urethral or cervical swabs (the old technique which was painful and uncomfortable) and are quickly becoming standard practice. Urine testing, as opposed to swab testing, makes it easier for people to undergo STI testing as part of their regular medical care. To collect the specimen for testing, YOU JUST HAVE TO PEE!

Here are the steps starting from
Registration >> Receive label sticker and container >> go to the toilet
>> do not wipe or clean your penis/vagina >> open the urine cup >> pee the first stream urine until it’s filled halfway
>> place urine cup in specimen bag >> wash your hands with THANN hand wash and water
>> pass it to staff at the counter >> pay >> confirm email address >> Sashay away

**For urinalysis, please do not urinate for at least an hour before your appointment for an accurate result**

SIMPLE SUMMARIZATION

• Our STD PCR Multiplex is the most advanced technology to detect multiple infections all at one test.
• Our STD PCR Multiplex include 14 infections in different locations;
  • Gonorrhea, Chlamydia, Syphilis, Chancroid, Lymphogranuloma Veneruem (LGV)
  • Herpes Simplex type 1 (HSV-1), Herpes Simplex type 2 (HSV-2)
  • Trichomonas vaginlis
  • Mycuplasma hominis, Mycoplasma genitalium, Ureaplasma Parvum, Ureaplasma urealyticum.
  • Cytomegalovirus (CMV)
  • Varicella-Zoster Virus (VZV)
• Our STD PCR Multiplex can detect infections in different locations;
  • Throat and oral cavity
  • Male and female urethra
  • anorectal area
  • vagina and cervix
  • sperm
  • skin lesions

• If you want to look for any possible infection in your urethra and urinary tract, you have to chose URINE PCR 14 infections which you will have to pass the urine.
• If you performed oral sex and want to check any possible infection in your throat, you have to chose THROAT SWAB PCR 14 infections which will be assisted by our staff.
• If you happen to be female who enjoy anal sex without condom, men who have sex with men, and bottom for anal sex without condom, then you have to chose ANAL SWAB PCR 14 infections which will be assisted by our staff.
• If  you are female who have vaginal sex, then you have to chose Vaginal Swab PCR 14 infections, which will be assisted by our staff.

HOW LONG DO I HAVE TO WAIT FOR RESULTS OF URINE PCR AND SWAB PCR?

• Basic/standard results take 3 to 5 working days. Elite packages get results same day.
• For normal PCR for 14 infections service, PCR test process takes 7 days.
• But we are able to speed up the laboratory and their process so that we have faster results from same day, next day result and 3 days result with additional cost.
• The results will be sent to your email address given to our clinics or you can check the result online on PULSE ONLINE PORTAL or E-DOC mobile application.

Pricelist

• Prices are in Thai Baht
• Price per one location of testing
• Online results will be available at PULSE Online Portal (POP) and E-Doc mobile application