HIV medicine accounts for approximately 18 per cent of the SCE Infectious Diseases exam — the single largest topic. BHIVA (British HIV Association) guidelines are the primary UK reference. This page summarises the high-yield content for exam preparation.
When to start ART
BHIVA recommends offering ART to all people living with HIV regardless of CD4 count. This recommendation is based on the START trial, which demonstrated that immediate treatment (regardless of CD4 count) reduces serious AIDS-related and non-AIDS-related events compared with deferred treatment (starting at CD4 below 350). The exam tests the principle of universal treatment — deferring ART until CD4 drops below a threshold is no longer recommended.
Treatment should be started as soon as the patient is ready, ideally within two weeks of diagnosis. Rapid or same-day ART initiation is recommended for patients presenting with certain opportunistic infections (PJP, toxoplasmosis) or with a CD4 count below 200, where delay increases mortality risk. The exception is cryptococcal meningitis, where ART should be deferred for four to six weeks after initiating antifungal therapy to reduce the risk of immune reconstitution inflammatory syndrome (IRIS).
The cryptococcal meningitis exception is heavily tested — it is the main scenario where delaying ART is the correct answer.
First-line ART regimens
BHIVA recommends an integrase inhibitor-based regimen as first-line for most treatment-naive patients. The preferred regimens are dolutegravir plus tenofovir alafenamide plus emtricitabine, or bictegravir plus tenofovir alafenamide plus emtricitabine (available as a single-tablet regimen). Dolutegravir plus lamivudine (two-drug regimen) is also recommended for patients with viral load below 500,000 copies per mL and no hepatitis B co-infection.
The shift from efavirenz-based regimens (previously first-line) to integrase inhibitor-based regimens is important exam content. Efavirenz is no longer first-line due to CNS side effects and a lower genetic barrier to resistance compared with dolutegravir.
Tenofovir alafenamide (TAF) has largely replaced tenofovir disoproxil fumarate (TDF) in first-line regimens due to a better renal and bone safety profile. However, TDF remains preferred for patients with or at risk of hepatitis B co-infection (because of its potent anti-HBV activity) and in specific cost-sensitive contexts.
Resistance testing
BHIVA recommends baseline genotypic resistance testing for all patients before starting ART. Treatment should not be delayed while awaiting resistance results if the patient is clinically unwell or has a very low CD4 count — start the empirical regimen and adjust when results are available.
If resistance to integrase inhibitors is detected (rare in treatment-naive patients but possible in transmitted resistance), alternative first-line options include boosted protease inhibitor-based regimens (darunavir with ritonavir or cobicistat) or NNRTI-based regimens (rilpivirine if viral load below 100,000 and CD4 above 200).
Resistance testing should also be performed at the time of virological failure — defined as two consecutive viral loads above 200 copies per mL at least four weeks apart in a patient on ART for at least six months.
Opportunistic infection prophylaxis
Primary prophylaxis against PJP (Pneumocystis jirovecii pneumonia) is recommended for all patients with a CD4 count below 200 cells per microlitre. The standard prophylaxis is co-trimoxazole 960 mg daily or 480 mg daily. Prophylaxis can be discontinued when the CD4 count has been above 200 for at least three months on ART.
Primary prophylaxis against toxoplasmosis is recommended for patients with a CD4 below 200 who are Toxoplasma IgG positive. Co-trimoxazole at the PJP prophylaxis dose also provides toxoplasmosis prophylaxis.
Primary prophylaxis against MAC (Mycobacterium avium complex) is recommended for patients with a CD4 below 50 using azithromycin 1,250 mg weekly or 600 mg twice weekly.
The CD4 thresholds for starting and stopping prophylaxis are commonly tested — know the numbers precisely.
PrEP
Pre-exposure prophylaxis is recommended for individuals at high risk of HIV acquisition. In the UK, PrEP is available free through sexual health clinics. The standard regimen is daily tenofovir disoproxil plus emtricitabine. Event-based (on-demand) dosing is an alternative for men who have sex with men — two tablets 2 to 24 hours before sex, one tablet 24 hours after the first dose, and one tablet 48 hours after the first dose.
PrEP requires baseline and regular monitoring — HIV testing (to exclude existing infection before starting), renal function, hepatitis B serology, and STI screening.
Prevention of mother-to-child transmission
All pregnant women living with HIV should be on ART regardless of CD4 count. If already on effective ART with an undetectable viral load, continue the current regimen (unless it contains dolutegravir, which should be discussed in the context of neural tube defect risk in the first trimester — though the absolute risk is now considered low).
If not on ART, start immediately — the goal is an undetectable viral load by the time of delivery. If the viral load is undetectable at 36 weeks, vaginal delivery is recommended. If the viral load is above 50 copies per mL at 36 weeks, planned caesarean section at 38 weeks is recommended.
Infant post-exposure prophylaxis with zidovudine (and additional agents if maternal viral load was detectable) is given for four weeks after birth. Breastfeeding is supported in the UK for women on effective ART with an undetectable viral load, with careful monitoring — this is a recent BHIVA guideline change that the exam may test.
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