History and exam

Key diagnostic factors

common

presence of risk factors

Blood transfusion, receptive or insertive anal or vaginal intercourse, receptive fellatio, needlestick injury, sharing of injecting equipment, and mucous membrane exposure within 72 hours from an infected source are risk factors.

exposure to HIV within past 72 hours

Guidelines indicate that post-exposure prophylaxis is effective only if the exposure has occurred within the previous 72 hours; the risk of source must be assessed.[3]

breakage, slippage, or non-usage of a condom

Increases exposure to infected body fluid. There is no indication for post-exposure prophylaxis with intact condom use.

history of ejaculation from source

Ejaculation from a high-risk or HIV-infected source increases risk of transmission.

trauma or skin break

Visible blood or trauma increases likelihood of exposure. Deep injury, visible blood, or injury with a device that has been used intravascularly all increase the risk of HIV transmission.[3] If the skin remains intact, there is no risk of HIV transmission.[3] 

genital ulcers

Current genital symptoms are important to assess. Presence of genital ulcer disease increases chances of HIV transmission from a source.

source from high-risk group for HIV viraemia

High-risk groups for HIV viraemia include people who inject drugs, commercial sex workers, men who have sex with men, and those with a history of other STIs.[3]

source from geographical area with high HIV prevalence

Prevalence of HIV in a geographical region may be helpful when confronted with a source of unknown HIV status. Regional prevalence can be obtained from the Joint United Nations Programme on HIV/AIDS (UNAIDS). UNAIDS data 2020 Opens in new window

high-risk sexual history in exposed person

Sexual encounters during the last 3 months should be assessed to determine the patient's risk of acquiring HIV inside the 3-month window period. Questions to ask include: the sex and country of origin of the most recent sexual partners; whether the partners were casual or regular; the type of sexual intercourse; and whether there was ejaculation and proper condom use.

If exposure is ongoing or repeated, referral for counselling should be considered.

uncommon

detectable HIV viral load in source

Risk of HIV transmission is associated with the level of viraemia. If the source is established on HIV treatment and virally suppressed (HIV viral load <200 copies/mL), there is effectively no risk of sexual HIV transmission.[44][45]

Other diagnostic factors

common

history of negative HIV test in source

If the source has had a negative HIV test in the recent past, this may be reassuring. The period for HIV testing and the source's risk in the window period must be taken into account.

uncommon

source with hepatitis co-infection

Co-infection with either hepatitis B or hepatitis C is associated with likelihood of HIV infection.

antiviral HIV resistance in source

It is important to note which antiretrovirals the source is taking and whether there is any known HIV viral resistance, as this is essential in drug selection. If this information is available, it may guide drug selection if post-exposure prophylaxis is indicated.

current prescription or non-prescription medications

Some medications, such as rifampicin and antiepileptics, reduce the efficacy of some antiretroviral medications, and certain antiretroviral medications can reduce or increase systemic levels of other medications, such as oral contraceptives.[52] Any medication that the person takes should be checked for interactions, and the post-exposure prophylaxis regimen should be chosen accordingly. Over-the-counter medications, such as St John's wort, also interact with antiretrovirals, and a history of current use should be elicited. Antacids containing aluminium or magnesium should be avoided with raltegravir, and the timing of dolutegravir administration should be adjusted with medications containing polyvalent cations.[50][51]

history of drug allergies

Helps to determine post-exposure prophylaxis regimen.

flu-like illness

Mononucleosis-like or flu-like illness with fever, sore throat, rash, diarrhoea, or other symptoms may occur with primary HIV infection or seroconversion. This may occur up to 12 weeks after exposure. Under this circumstance, 3rd-generation HIV-antibody enzyme-linked immunosorbent assay (ELISA) testing may be negative, but an elevated viral load or 4th-generation HIV antigen/antibody test will confirm the diagnosis. Viral load testing is not routinely done in all patients undergoing post-exposure prophylaxis evaluation.[54][55]

Risk factors

strong

blood transfusion from HIV-positive donor

There is an up to 100% estimated risk of HIV transmission with blood transfusion (1 unit) from an HIV-positive person.[14]

sharing injecting equipment

There is a 0.67% estimated risk of HIV transmission from an HIV-positive person.[23]

needlestick injury

There is a 0.3% estimated risk of HIV transmission from a needlestick injury from an HIV-positive person.[31][32][33]

receptive anal intercourse

There is a 0.1% to 3.0% estimated risk of HIV transmission from an HIV-positive person.[15][16]

receptive vaginal intercourse

There is a 0.1% to 0.2% estimated risk of HIV transmission from an HIV-positive person.[16][17][18][19][20][21]

weak

mucous membrane exposure

There is a 0.09% estimated risk of HIV transmission from an HIV-positive person.[24]

insertive anal intercourse

There is a 0.06% estimated risk of HIV transmission from an HIV-positive person.[22]

insertive vaginal intercourse

There is a 0.03% to 0.09% estimated risk of HIV transmission from an HIV-positive person.[19]

receptive oral sex (fellatio)

There is a 0% to 0.04% estimated risk of HIV transmission from an HIV-positive person.[22]

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