U13C3 HIV And TB Flashcards
What is mycobacterium tuberculosis?
What are the risk factors for TB?
-Socioeconomic status – poverty, overcrowding, poor living conditions, malnutrition, lack of adequate healthcare, incarceration
- Overall health/immune system status: immune suppression, HIV co-infection, diabetes, TB within the last 2 years, transplant patients, malignancy
- Alcoholism
- Smoking
- Drug users
- Mental health often overlooked (delay seeking care, miss doses etc.)
- Health Care Workers – (Cat 3 organism)
- Genetic Predisposition
What are the symptoms for TB?
Pulmonary
Most TB infections will affect the lungs and the main symptoms:
- Persistent, usually productive cough that lasts >3weeks
- Haemoptysis is a late sign – for blood to be coughed up, TB infection would be extensive in the lungs
- Breathlessness that gradually gets worse
- If there is laryngeal involvement, patients may also have a hoarse voice
- If involvement of pleura, pleuritic pain is also a presenting complaint
Signs
- CXR can show consolidation
- Sputum samples (collected on at least 3 occasions) tested and if smear-positive for TB, patients are considered infectious
Extrapulmonary
Symptoms vary depending on the organ system affected:
- Persistently swollen glands – LN TB
- GITB – intestinal TB occurs due to reactivation of primary disease
Abdo pain, weight loss, anaemia, fever with night sweats, obstruction, R iliac fossa pain, - MSK – haematogenous spread
Mtb invades joint synovium and caseating granulomas form leading to destruction of cartilage and adjacent bone
Night sweats, anorexia and weight loss - CNS in TB meningitis (chronic meningitis) – haematogenous spread
Seizures (fits)
Photophobia
Reduced conscious level
Persistent headache - Pericardial TB is where TB has caused constrictive pericarditis – haematogenous spread
Reduced ventricular filling
Systemic venous congestion (ascites, raised JVP)
Pulmonary venous congestion (dyspnoea, cough, orthopnoea)
How is TB detected?
Combination of clinical and chest X-ray findings, with or without acid fast bacilli (AFB)
- At least 2 separate sputum (or BAL) samples (previously 3) for AFB microscopy & culture (1x a.m)
- Specimens can be contaminated with resident flora so require a decontamination step before culture
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CD4 Cell Count and Percentage:
- Purpose: Measures the number and percentage of CD4+ T lymphocytes, which are crucial for immune function. It helps assess the status of the immune system, particularly in individuals with HIV/AIDS.
- Abnormal Result: A low CD4 count indicates immunosuppression and increased susceptibility to opportunistic infections. It may necessitate initiation or modification of antiretroviral therapy (ART).
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Serum AST (Aspartate Aminotransferase) and ALT (Alanine Aminotransferase):
- Purpose: Liver enzymes released into the bloodstream when liver cells are damaged. These tests assess liver function and help diagnose liver diseases, such as hepatitis and liver cirrhosis.
- Abnormal Result: Elevated AST and ALT levels indicate liver damage or disease, which could be due to various causes including viral hepatitis, alcohol consumption, or medication toxicity.
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Bilirubin:
- Purpose: Measures the level of bilirubin, a waste product from the breakdown of red blood cells. Elevated levels may indicate liver dysfunction or obstruction of the bile duct.
- Abnormal Result: High bilirubin levels can indicate liver disease, bile duct obstruction, or hemolytic disorders. Jaundice, a yellowing of the skin and eyes, may be present.
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Alkaline Phosphatase:
- Purpose: Measures the level of alkaline phosphatase enzyme in the blood, which is produced by the liver, bones, and other tissues. Elevated levels may indicate liver or bone disorders.
- Abnormal Result: Elevated alkaline phosphatase levels can indicate liver disease, bile duct obstruction, bone disorders (e.g., bone metastasis or Paget’s disease), or certain medications.
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Creatinine and Estimated Glomerular Filtration Rate (eGFR):
- Purpose: Creatinine is a waste product from muscle metabolism excreted by the kidneys. eGFR estimates the kidney’s filtration rate. These tests assess kidney function.
- Abnormal Result: Elevated creatinine levels and reduced eGFR indicate impaired kidney function, which can result from conditions like kidney disease, diabetes, or high blood pressure.
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Platelet Count:
- Purpose: Measures the number of platelets in the blood, which are essential for blood clotting.
- Abnormal Result: Low platelet count (thrombocytopenia) can indicate various conditions such as immune thrombocytopenia, liver disease, bone marrow disorders, or certain medications. High platelet count (thrombocytosis) may be associated with inflammatory conditions or blood disorders.
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Hepatitis B & C Serology and Liver Function Tests:
- Purpose: Serology tests detect antibodies or antigens related to hepatitis B and C viruses, while liver function tests assess liver enzymes and bilirubin levels to diagnose and monitor liver diseases.
- Abnormal Result: Abnormal serology or liver function test results may indicate acute or chronic hepatitis B or C infection, liver inflammation, cirrhosis, or hepatocellular carcinoma.
What are the outcomes after exposure to TB?
Where are the infection sites?
What are the 4 potential fates of inhaled TB?
- No chance of active TB
- Primary TB
- Latent infection
- Reactivation TB
How does outcome 1 result in the immune system eliminating the bacteria?
How does outcome 2 result in primary active TB?
What immune cells are involved in TB?
How does outcome 3 result in latent TB?
How does outcome 4 result in reactivated TB?
How is TB treated and prevented?
Active TB without central nervous system involvement:
- Rifampicin, isoniazid (with pyridoxine), Pyrazinamide and Ethambutol for 2 months then
- Isoniazid (with pyridoxine) and Rifampicin for a further 4 months
Active TB with central nervous system involvement:
- Rifampicin, isoniazid (with pyridoxine), Pyrazinamide and Ethambutol for 2 months then
- Isoniazid (with pyridoxine) and Rifampicin for a further 10 months
Latent TB:
3 months of isoniazid (with pyridoxine*) and rifampicin
OR
6 months of isoniazid (with pyridoxine*)
Base the choice of regimen on the person’s clinical circumstance:
- If interactions with rifamycins are a concern, i.e., with HIV (drug interactions) or those who have had a transplant
- If hepatoxicity is a problem shorter treatments + rifampicin
As Mtb bacteria are very slow-growing, antibiotics must be taken for a long time—for 4 to 6 months or longer. Treatment must be continued long after people feel completely well. Otherwise, tuberculosis tends to recur as it was not fully eliminated
Latent vs active TB
Primary vs secondary TB
Primary Tuberculosis:
- The infection of an individual who has not previously been infected
- Occurs usually within the first 2 years after exposure
- Most common in children
Secondary Tuberculosis:
- The infection of an individual who has been infected in the past, and this is “flare up” of TB
- Often occurs due to factors such as reduced immunity, poor nutritional status, alcoholism, drug use, or advancing age
What is direct observed therapy?
What is the structure of HIV?
What is the pathophysiology of HIV?
What are the symptoms of HIV at the different stages?
What is the pathophysiology of TB?
- Both the Ghon focus and the Ghon complex can be associated with the initial stages of infection, which may eventually lead to either latent TB or active TB, depending on the immune response of the individual.
- Ghon Focus is the primary lesion caused by Mtb infection. It represents the initial site of infection and the body’s
localised immune response to contain the bacteria. The Ghon focus typically consists of granulomatous inflammation, which can occur soon after the initial infection. - When the Ghon focus is associated with involvement of the regional lymph nodes (i.e., the lymph nodes that drain the area of the lung where the Ghon focus is located), it forms a Ghon complex. This indicates that the infection has spread from the initial site in the lung to the lymphatic system, but the body’s immune response is attempting to contain it. The lymph nodes involved in the Ghon complex may become enlarged and inflamed as they try to contain the bacteria.
- In active TB, the bacteria have managed to replicate and spread, causing symptoms and potentially infecting other parts of the body beyond the initial Ghon focus and Ghon complex. This progression can lead to more extensive lung damage, caseous necrosis, and the formation of cavities within the lung tissue as the disease progresses.
- In the case of latent TB, the infection is successfully contained by the body’s immune system. The bacteria remain in the
body but are inactive and do not cause symptoms or spread to others. During this latent phase, the Ghon focus, or Ghon complex may heal, with the potential for calcification indicating a past, contained infection. This is a Ranke complex. The presence of a Ghon focus or Ghon complex in someone with latent TB suggests a previous encounter with TB bacteria that did not progress to active disease, due to the effectiveness of the immune response. - Caseous necrosis is not typically associated with latent tuberculosis infection (LTBI). In the latent stage of TB, the Mtb bacteria are still viable, but contained within granulomas by the body’s immune system, and remain inactive, not causing any symptoms or tissue damage, including caseous necrosis. Caseous necrosis is typical of active tuberculosis disease, where the immune response to active bacterial replication leads to the characteristic tissue damage and necrosis.
- The presence of a Ghon focus or Ghon complex alone does not distinguish between latent TB and active TB disease. The distinction is based on the activity of the infection and whether the bacteria are dormant or actively replicating and the presence or absence of symptoms.
How does the BCG vaccine work?
What are the signs and symptoms of HIV?
What are the risk factors for HIV?
How is HIV monitored?
What is IGRA and TST?
