Viruses from a Blood Test: HIV, Hepatitis B, Hepatitis C. Hepatitis B & C are more likely to be caught through blood to blood contact (contaminated needles for example, or from overseas) than sexually.
Syphilis, a bacteria, is also tested from a blood sample.
Are there tests for genital warts or genital Herpes?
There is no practical STD testing for genital warts – you either have them or you don’t. Rarely, the diagnosis be uncertain, however, and biopsy may be performed.
There is also no practical screening test for genital herpes in people without symptoms because 80% of people test positive on a blood test to past exposure to the HPV virus. However, active lesions are easily tested with a swab for viral DNA. There are two types of HSV: Type 1 and Type 2. A swab will distinguish the two types. Type 1 Herpes virus is the classical cause of cold sores (around or inside the mouth). Type 2 HSV is the classical “genital” type. There is a lot of overlap, and both types can cause mouth or genital herpes.
There are situations when a blood test for Herpes may be useful. Let’s take a common scenario of somebody with recurrent genital herpes who is concerned about passing it on to their partner. In this example, the person with recurrent genital herpes has a blood test and is positive for Type 2 antibody. Their partner is offered a blood test. The partner who tests negative for Type 2 HSV would then be susceptible to infection. Based on these results, the person with recurrent herpes may wish to take daily anti-viral medication and thereby reduce the risk of transmission to the partner.
How are the samples collected for a routine STD Check?
There are two types of test required for a full STD Check
- Urine Test and/or swabs that may be self-taken – for Chlamydia, Gonococcus, Trichomoniasis and perhaps Mycoplasma
- Blood Test – for HIV, Syphilis & Viral Hepatitis
The urine sample is a ‘first pass’ sample. The idea is for the urine to flush through any bugs hiding in the urethra (the end of the urinary tract). Therefore, the urine is collected at least 20 minutes after you last went. Only the first part of the urine is collected. Fill the container to around a third full (20 to 30mls). You then empty the rest of your bladder into the toilet.
A self-taken vaginal swab is more sensitive than a urine test in women. The self taken dry swab is simply inserted around 2-3 inches into the vagina and gently rotated for around half a minute. The clinic will provide you with the swab and form and drop the sample off at your chosen pathology provider.
Men who have Sex with Men
Standard MSM STD guidelines recommend blood testing for Syphilis, Hepatitis B, Hepatitis C & HIV. Swabs should also be collected for Gonococcus & Syphilis. There is now good evidence to support self-taken samples¹ and the doctor will discuss this option with you. Self collection samples are taken in the privacy of your own home and then taken to your pathology provider of choice.
What type of STD blood test does the laboratory perform?
HIV tests performed in Australian accredited laboratories are “4th generation” and these HIV tests that are positive between 2 and 6 weeks after exposure.
Hepatitis B: The Hepatitis B surface antigen (HepBsAg) is a screening test for previous exposure to hepatitis B infection. For those at high risk for hepatitis B, additional tests may be requested: anti hepatitis B core antibody (anti-HBc) & anti hepatitis B surface antibody (anti-HBs). Around 1% of Australians are Hepatitis B positive – of whom around half are not aware they have the diagnosis. Hepatitis B is more likely to be caught from previous “blood to blood contact” such as contaminated needles than sexually.
Hepatitis C: The Hepatitis C screening test is Hepatitis C Viral antibody (HCV antibody). Just under 1% of Australians are hepatitis C positive – of whom around 15% are not aware they have the diagnosis. Hepatitis C is more likely to be caught from previous “blood to blood contact” such as contaminated needles than sexually.
Syphilis testing: Antibody to the bacteria (Treponema) will detect past infection. Note that (only) 75% of people with a primary ulcer caused by Syphilis (primary chancre) will have a positive blood test – so anyone with a possible Syphilis ulcer will need a simple swab taken from the ulcer base.
What’s the best test for early HIV infection?
Antibodies to HIV take 6 to 12 weeks after exposure to become positive – so you have to wait at least 6 weeks for the 3rd generation HIV test.
The fourth generation test combines an Antibody test with the p24 Antigen. The 4th generation test is positive within 1 month of exposure (often from 2 to 3 weeks) and is the most commonly performed test in Australia.
A positive HIV test will only be known for sure after a second confirmatory test. The first test is a screen and may be falsely positive. The second test will distinguish HIV 1 from HIV 2.
What’s the best test for Syphilis?
The pathology provider will perform various tests “behind the scenes” depending on the initial blood result. These tests include Syphilis antibody, RPR and TPPA. The possible outcomes are negative, active syphilis infection or latent syphilis. Note that a negative blood test does not rule out syphilis in the early days and may need to repeated.