Maxi CBL - HIV

Question 1

What are the criteria that correlate with systemic inflammatory response syndrome (SIRS)? [4]

Answer 1

1. Temperature <36 or >38,
2. Heart rate >90bpm,
3. RR >20,
4. WCC <4 or >12

Question 2

What is the difference between severe sepsis and septic shock? [2]

Answer 2

1. Severe sepsis = Sepsis with organ dysfunction, hypoperfusion or hypotension
2. Septic shock = Sepsis with refractory hypotension

Question 3

What are the differential diagnoses to HIV infection? [8]

Answer 3

1. Typical CAP
   
   • Strep pneumoniae
   • Haemophilus influenzae
2. Atypical CAP
   
   • Legionella,
   • Mycoplasma pneumoniae,
   • Chlamydia pneumoniae
3. Infections in the immunocompromised host
   
   • PCP,
   • TB,
   • Cryptococcal disease,
   • Staphylococcal pneumonia
4. Infective exacerbation of underlying/undiagnosed fibrosis or reversible lung disease i.e. COPD, cystic fibrosis
5. Likely underlying immunosuppression due to poor response to initial treatment, history of shingles and unexplained diarrhoea and oral thrush on exam
   
   • HIV, steroid use, malignancy, common variable immunodeficiency

Question 4

What investigations do you want to carry out on a patient with suspected HIV? [3]

Answer 4

1. Sputum for MC/S, virology, AAFB, induced sputum with physiotherapy if unable to expectorate
2. CT chest
3. HIV test

Question 5

How can HIV be transmitted? [7]

Answer 5

1. Unprotected sexual intercourse
2. Intravenous drug abuse
3. Blood transfusion
4. Needlestick injury/IM/SC/IV injection
5. Tattoo/piercing
6. Vertical transmission depending on treatment
7. Mucous membrane exposure

Question 6

What factors would make a patient “high risk” for HIV? [5]

Answer 6

1. high HIV viral load,
2. trauma (including sexual assault),
3. co-existing STIs,
4. ulcerative conditions
   
   • i.e. herpes simplex/syphilitic chancre
5. if the index male is uncircumcised

Question 7

From transmission rates and epidemiology, what are the typical high risk groups for HIV? [6]

Answer 7

1. Men who have sex with men (MSM) who have had unprotected sex
2. Individuals from high prevalence countries with sexual or vertical transmission risk
   
   • Sub-Saharan Africa,
   • South East Asia,
   • Eastern Europe,
   • South/Central America and Caribbean
3. IVDU, especially those from high prevalence areas
4. Individuals exposed to blood via IV/SC/IM injection, tattoo, piercing of blood transfusion in high risk countries or non professional settings
5. Sexual contacts of the above
6. Anyone diagnosed with a STI

Question 8

What are the potential barriers to HIV testing?

• patient barriers? [5]
• doctor barriers? [6]

Answer 8

• Patient barriers
  
  1. May not think they are at risk
  2. Worried regarding confidentiality, stigma, immigration issues
  3. Employment issues, may fear they will lose their job especially if health care worker
  4. Criminalisation issues
  5. Insurance
• Doctor barriers
  
  1. May not think of testing or be aware of clinical indications for testing
  2. May assume patient is not at risk
  3. Fear of embarrassing or offending patient especially if taking sexual history
  4. Lack of time
  5. Perceived lack of counselling skills
  6. Logistic issues to get result back to patient

Question 9

What is PCR? [2]

Answer 9

1. Polymerase chain reaction is a molecular biology technique which amplifies a specific DNA sequence generating multiples copies
2. It is a very sensitive and specific technique for diagnosing viruses, overtaking viral culture, serology and IHC

Question 10

Describe the opportunistic infection caused by P. jirovecii under the following headings:

1. who gets it? [1]
2. pathological features? [4]
3. diagnosed via? [4]
4. complications? [2]
5. treatment? [2]

Answer 10

1. Who gets it?
   
   • immunocompromised individuals
2. Pathological Features:
   
   • extracellular pathogen causing interstitial plasma cell pneumonia with “foamy” exudates in the alveoli.
   • causes progressive and disproportionate SOB, fever, dry cough with failure to respond to usual antibiotic regimes.
   • usually few signs on examination or CXR, although classically causes perihilar interstitial shadowing in moderate disease.
   • can cause white out in severe disease
3. Diagnosed via:
   
   • induced sputum
   • bronchoalveolar lavage (BAL)
   • biopsy
   • PCR of sample performed.
4. Complications:
   
   • respiratory failure,
   • pneumothorax,
5. Treatment:
   
   • First line treatment is cotrimoxazole 120mg/kg TDS and steroid therapy

Question 11

How do you define an opportunistic infection? [1]

Answer 11

1. Organisms which do not usually cause infection but do so when host defenses are compromised.
2. Includes viral, bacterial, fungal, protozoal and helminth infections i.e. CMV, Candida, PCP, Toxoplasma

Question 12

Describe the virology tests that are used to diagnose HIV [4]

Answer 12

1. HIV antibody test is the traditional method for diagnosis.
   
   • Most patients will develop antibodies within 6-8 weeks with almost 100% at 3 months, hence the 3 month window period for HIV testing.
2. An ELISA test is performed first and then confirmed with Western Blot.
   
   • ELISA is enzyme linked immunosorbent assay which uses an antigen-antibody reaction to generate a signal and result.
   • Western blot uses gel electrophoresis to demonstrate specific HIV proteins.
3. HIV p24 antigen testing is used with a confirmatory antibody test.
   
   • This detects p24 protein which is present on the surface of the virus.
   • This can be positive as early as 3 weeks.

Question 13

What is an HIV viral load? [1]

Answer 13

a measure of HIV RNA in the plasma

Question 14

What is CD4, what is a CD4 count and what is the normal range of a CD4 count? [4]

Answer 14

1. CD4 count is a measure of the number of T helper cells expressing CD4 on their cell surface.
2. CD4 is a glycoprotein expressed on the surface of T helper cells, as well as monocytes, macrophages and dendritic cells.
   
   • It is involved in T cell activation and interacts with MHC Il molecules on antigen presenting cells being involved in both cell mediated and humeral immunity.
3. The normal range is 500-1000.

Question 15

List the HIV/AIDs-defining conditions under the following headings:

1. Respiratory [2]
2. Neurology [4]
3. Dermatology [1]
4. Gastroenterology [1]
5. Oncology [1]
6. Gynaecology [1]
7. Ophthalmology [1]

Answer 15

1. Respiratory:
   
   • Tuberculosis
   • Pneumocystis
2. Neurology:
   
   • Cerebral toxoplasmosis
   • Primary cerebral lymphoma
   • Cryptococcal meningitis
   • Progressive multifocal leucoencephalopathy
3. Dermatology
   
   • Kaposi’s sarcoma
4. Gastroenterology
   
   • Persistent cryptosporidiosis
5. Oncology
   
   • Non-Hodgkin’s lymphoma
6. Gynaecology
   
   • Cervical cancer
7. Ophthalmology
   
   • Cytomegalovirus retinitis