HIV Tests

A full range of HIV tests are available. Depending on risk level and time from exposure, the following tests may be appropriate :

Time from exposure

Available Tests


0 – 10 days

Consider HIV PEP if exposure is high risk; Otherwise, consider testing based on timelines  below.


10 – 14 days

HIV PCR Usually 7-10 working  days

15 – 28 days

HIV P24 Antigen / Antibody test ( also known as HIV Combo test / HIV Duo test )

  • HIV Combo lab test
  • Abbott Bioline p24 Ag/Ab Combo ( rapid ) test

$120-180 ( incl GST )
usually 1-3 working  days

about 20 min

28 days

HIV P24 Antigen / Antibody test ( as above )

HIV antibody tests

  • ELISA-type antibody test
  • Oraquick ( saliva ) rapid test
  • Abbott Bioline HIV 1/2 3.0  ( fingerprick ) rapid test

From $120


From $36  ( incl GST )

about 20 min

3 months and beyond

HIV antibody tests ( as above )


Most circumstances which may expose you to HIV may also expose you to other STIs. You may wish to consider testing for other STIs.

Do note that there may be changes to our clinic schedule from time to time. Please click  for the latest updates.

What is the risk of HIV?
This question may be one of the most common ones from patients coming for HIV counselling and testing. And yet this is probably one of the most difficult questions to answer. Do a search on the internet and you may find numerous websites, from official US CDC ( Centers for Disease Control & Prevention ) sites to Q&A websites, which give a range of figures pertaining to the risk of HIV transmission via various forms of sexual acts. Unfortunately, these figures may not always be the same. The reason for this includes :

  • Patients or subjects of research often engage in multiple different sex acts in each sexual encounter.
  • Patients or subjects of research may engage in multiple encounters ( either reported or unreported, involving different sex acts each time ) within a short period of time, in between getting their HIV tests done.
  • There is inherent difficulty in doing research and getting precise statistics in a discipline which is very private and often still carries significant stigma. Much of the information on number of partners and types of sex acts depend on subjects’ self-reporting.

To simplify the issue, we have categorised the various sexual and non-sexual exposures based on their approximate risk level. Bear in mind that there can be several factors which increase or decrease the risk, even within each category. Where figures are available and likely to be reliable, we have quoted the lowest and highest estimated risk from various sources but we believe that the risk category is likely to be more relevant for patients trying to understand their chances of infection.

Risk CategoryType of Exposure ( assuming partner is HIV positive )Remarks
Very high riskBlood transfusion of infected blood>90%
Needle sharing amongst IV drug users0.67%
Receptive anal sex0.4% – 3.38%
Moderate to high riskReceptive vaginal sex0.08% to 0.19%
Insertive anal sex0.06% – 0.62%
Insertive vaginal sex0.03% – 0.1%
Low riskReceptive oral sexExtremely rare
Negligible / Theoretical risk( theoretically possible but extremely unlikely and no well-documented cases )

Insertive oral sex‘Rimming’ / Peri-anal licking

Sharing sex toys



Throwing body fluids eg. semen/saliva

No documented cases; carries risk of other STIs if unprotected

Carries risk of other STIs

Carries risk of other STIs

Risk of wound infection

Factors which increase the risk

Presence of a concomitant STIPresence of sores or wounds or ulcers

High viral load in partner

With ejaculation ( for receptive partner )

Factors which reduce the riskAnti-retroviral ( ARV ) treatment in affected partner96% reduction(1)
Consistent and correct condom use80% reduction(2)
Male circumcision50-60% reduction ( in female-to-male transmission)

1 Cohen MS, Chen YQ, McCauley M, et al; HPTN 052 Study Team. Prevention of HIV-1 Infection with early antiretroviral therapy. N Engl J Med 2011;365(6):493-505.
2 Weller SC, Davis-Beaty K. Condom effectiveness in reducing heterosexual HIV transmission (Review). The Cochrane Collaboration. Wiley and Sons, 2011.

Below: Oraquick HIV rapid test – positive test

What do i do if the test turns out positive?
If the initial screening test is positive, a second blood sample will need to be sent for a confirmatory test called the Western Blot. This test typically takes about 2 weeks to be ready. No fasting or other special preparation is required.

The Western Blot may show:

  • Negative ( good news! But consider repeating antibody test in 3 months if there has been risk of exposure )
  • Indeterminate ( Consider repeating antibody test or P24 Combo test in 1 month if there has been risk of exposure )
  • Positive ( Our doctor will discuss the subsequent options for treatment and follow up with you )

HIV is certainly a serious infection, but options now exist for patients to have the infection suppressed and controlled. This can help reduce or delay the late complications of HIV infection and help protect your sexual contacts from HIV. Therefore it is crucial to take the first step and be tested.

Some additional information is provided below, together with links to the original site / source.

1)  From the US CDC ( Centers for Disease Control and Prevention ) website

Estimated Per-Act Probability of Acquiring HIV from an Infected Source, by Exposure Acta
Estimated Per-Act Probability of Acquiring HIV from an Infected Source, by Exposure Acta
Type of ExposureRisk per 10,000
Blood Transfusion9,000b
Needle-sharing during injection drug use67c
Percutaneous (needle-stick)30d
Receptive anal intercourse50e, f
Receptive penile-vaginal intercourse10e, f, g
Insertive anal intercourse6.5e, f
Insertive penile-vaginal intercourse5e, f
Receptive oral intercourselowe, i
Insertive oral intercourselowe, i
Throwing body fluids (including semen or saliva)negligible
Sharing sex toysnegligible


a Factors that increase the risk of HIV transmission include sexually transmitted infections, early and late-stage HIV infection, and a high level of HIV in the blood. Factors that reduce the risk of HIV transmission include condom use, male circumcision, and use of antiretrovirals.
b Donegan E, Stuart M, Niland JC, et al. Infection with human immunodeficiency virus type 1 (HIV-1) among recipients of antibody-positive blood donations. Ann Intern Med 1990;113(10):733-739.
c Kaplan EH, Heimer R. A model-based estimate of HIV infectivity via needle sharing. J Acquir Immune Defic Syndr 1992;5(11):1116-1118.
d Bell DM. Occupational risk of human immunodeficiency virus infection in healthcare workers: an overview. Am J Med 1997;102(5B):9-15.
e Varghese B, Maher JE, Peterman TA, Branson BM, Steketee RW. Reducing the risk of sexual HIV transmission: quantifying the per-act risk for HIV on the basis of choice of partner, sex act, and condom use. Sex Transm Dis 2002;29(1):38-43.
f European Study Group on Heterosexual Transmission of HIV. Comparison of female to male and male to female transmission of HIV in 563 stable couples. BMJ 1992;304(6830):809-813.
g Leynaert B, Downs AM, de Vincenzi I; European Study Group on Heterosexual Transmission of HIV. Heterosexual transmission of HIV: variability of infectivity throughout the course of infection. Am J Epidemiol 1998;148(1):88-96.
h HIV transmission through these exposure routes is technically possible but extremely unlikely and not well documented.
i HIV transmission through oral sex has been documented, but rare. Accurate estimates of risk are not available.
j Pretty LA, Anderson GS, Sweet DJ. Human bites and the risk of human immunodeficiency virus transmission. Am J Forensic Med Pathol 1999;20(3):232-239.

2)  From the Canadian AIDS Treatment Information Exchange:

Risk of HIV Transmission From Different Types of Unprotected Sex
 Number of Individual StudiesRange of EstimatesMeta-Analysis Estimate
Receptive anal




Insertive anal



Receptive vaginal




Insertive vaginal




3)  From this UK-based patient information website, NAM ( National AIDS Manual ):

Estimated HIV transmission risk per exposure for specific activities and events

Vaginal sex, female-to-male, studies in high-income countries0.04% (1:2380)
Vaginal sex, male-to-female, studies in high-income countries0.08% (1:1234)
Vaginal sex, female-to-male, studies in low-income countries0.38% (1:263)
Vaginal sex, male-to-female, studies in low-income countries0.30% (1:333)
Vaginal sex, source partner is asymptomatic0.07% (1:1428)
Vaginal sex, source partner has late-stage disease0.55% (1:180)
Receptive anal sex amongst gay men, partner unknown status0.27% (1:370)
Receptive anal sex amongst gay men, partner HIV positive0.82% (1:123)
Receptive anal sex with condom, gay men, partner unknown status0.18% (1:555)
Insertive anal sex, gay men, partner unknown status0.06% (1:1666)
Insertive anal sex with condom, gay men, partner unknown status0.04% (1:2500)
Receptive fellatioEstimates range from 0.00% to 0.04% (1:2500)
Mother-to-child, mother takes at least two weeks antiretroviral therapy0.8% (1:125)
Mother-to-child, mother takes combination therapy, viral load below 500.1% (1:1000)
Injecting drug useEstimates range from 0.63% (1:158) to 2.4% (1:41)
Needlestick injury, no other risk factors0.13% (1:769)
Blood transfusion with contaminated blood92.5% (9:10)

Sources: vaginal sex;1 anal sex;2 fellatio;3 2 mother-to-child;4 other activities.5


  1. Boily MC et al. Heterosexual risk of HIV-1 infection per sexual act: systematic review and meta-analysis of observational studies. Lancet Infect Dis 9(2): 118-129, 2009
  2. Vittinghoff E et al. Per-contact risk of human immunodeficiency virus transmission between male sexual partners. American Journal of Epidemiology 150: 306-311, 1999
  3. Del Romero J et al. Evaluating the risk of HIV transmission through unprotected orogenital sex.AIDS 16(9): 1296-1297, 2002
  4. Townsend C et al. Low rates of mother-to-child transmission of HIV following effective pregnancy interventions in the United Kingdom and Ireland, 2000-2006. AIDS 22: 973-981, 2008
  5. Baggaley RF et al. Risk of HIV-1 transmission for parenteral exposure and blood transfusion. AIDS 20: 805-812, 2006

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Dear friends and patients, 

Thank you for your love and support for the past 11 years. Prudence Family Clinic will be moving to a new address in July 2024.

Our last day of operations at the current address is 30th June 2024. 

We remain in Bishan! Our new address is:   Blk 116 Bishan Street 12 #02-30 ( 2nd level ) s570116

We hope to resume operations in August 2024. The exact date of re-opening will be updated on this website.

Thank you once again, for giving us the opportunity to participate in your health journey.