TB and HIV Flashcards
Reading assignment: Principles of Pulm Med Chapters 24, 25, and 26 McConn KK and GM Viola. Tuberculosis Screening: Prevention in the Patient with Immunosuppression. JAAPA 2012; 25 (4): 29-30. 1. Discuss the epidemiology of tuberculosis. 2. Discuss the pathogenesis and clinical presentation of tuberculosis. 3. Describe methods used to address the prevention of tuberculosis, including screening methods. 4. Describe the diagnosis and treatment of tuberculosis infection, including latent tube
According to the WHO, where is the incidence of new TB cases the highest in the world?
Africa (the nation, not the continent)
Over the past 30 years or so, the incidence/reported TB Cases in the US has?
Significantly decreased
How do you diagnose a Latent TB Infection?
- PPD (Mantoux)
2. IGRA
When were these diagnostic testings for latent TB developed?
20th Century.
The bulk of the 20th century did not have this. Perhaps the screening allows for a decrease in TB prevalence?
Do latent infections show up on CXR?
Not necessarily!
What is the PPD Tuberculin Test?
Patient is injected SQ and told to come back in 48 hours to see if there is a reaction.
When is an induration of > or equal to 5 mm considered a positive reaction to a PPD/Mantoux Skin Test?
- People living with HIV
- Recent Close Contacts of People with Infectious TB
- People with CXR findings suggestive of previous TB dz
- People with organ transplants
- Other immunosuppressed patients.
When is an induration of > or equal to 10 mm considered a positive reaction to a PPD/Mantoux Skin Test?
- People who have recently come to the US from areas where TB is common
- People who inject drugs
- People who live or work in high-risk congregate settings
- Mycobacteriology laboratory workers
- People with certain medical conditions that increase risk for TB
- Children younger than 4 years old
- Infants, children, adolescents exposed to adults in high-risk categories
When is an induration of > or equal to 15 mm considered a positive reaction to a PPD/Mantoux Skin Test?
This is considered a positive reaction for people who have no known risk factors for TB.
How sensitive and specific is the PPD (aka Mantoux aka TST)?
Up to 20% of positive reactions might be false positives
What can lead to a false positive?
- Infected with a Mycobacteria other than TB (e.g. MAC)
- BCG Vaccination
- Administration of Incorrect Antigen
- Incorrect measuring or interpretation of TST reaction
What factors need to be considered when reading PPD tests?
- Prevalence of disease in the population
2. Geographic Area
Can the PPD/Mantoux/TST test give false negatives?
YES!
Who could get a false negative in a TST/PPD/Mantoux test?
- Critically Ill TB Pateint
- Immunosuppressed person
- Recently vaccinated with live virus (measles or small pox)
- Recent TB infection (within the past 8-10 weeks)
- Younger than 6 months of age
- Incorrect method of giving the TST
- Incorrect measuring or interpretation of TST reaction
What is the BCG Vaccine?
Bacillus Calmette–Guérin is a vaccine against tuberculosis that is prepared from a strain of the attenuated live bovine tuberculosis bacillus, Mycobacterium bovis, that has lost its virulence in humans.
Is there a way to distinguish if the positive on a PPD/TST/Mantoux test is Latent TB or BCG Vaccine?
No!
Individuals should always be further evaluated if they have positive TST
How long does it take for the body’s immune system to react to TB’s tuberculin?
2-8 weeks
What is IGRA?
Interferon-Gamma Release Assay
Whole-blood tests that can aid in diagnosing Mycobacterium tuberculosis infection, including both latent TB and TB dz
What are the three IGRAs that are available?
- QuantiFERON TB Gold test
- QuantiFERON TB Gold In-Tube Test
- T-SPOT TB test
Are IGRAs specific and sensitive?
Highly specific and highly sensitive (compared to PPD)
Which IGRA is more sensitive to immunocompromised patients?
TSPOT
What are the advantages of using IGRA?
- Requires a single patient visit to conduct the test
- Results can be available within 24 hours
- Does not boost responses measured by subsequent tests.
- Prior BCG vaccine does not cause a false-positive IGRA test result
What are the disadvantages of IGRA?
- Blood samples must be processed within 8-16 hours after collection while white blood cells are still viable
- Errors in collecting or transporting blood specimens or in running and interpreting the assay can decrease the accuracy of IGRAs
- Limited Data on the prediction who will progress to TB dz in the future
- Limited data on children < 5 years, persons with recently exposed M. tuberculosis, immunocompromised persons, serial testing.
- Tests may be Expensive
Treatment of LTBI (Latent TB Infection)
- INH 300 mg QD 9 months
- RIF 600 mg QD 4 months
- RBN 300 mg QD 4 months
What is an important factor in the clinical approach when attempting to dx ACTIVE TB?
PATIENT HISTORY!!!
What are appropriate clinical methods in making a dx of active TB?
- Symptoms (cough, fever, sweats, weight loss)
- CXR
- Sputum Studies
- Tissue or Fluid Samples
T/F If the patient is suspected to have active TB, the first line of confirmatory diagnosis would be to have a PPD Test completed.
False!
You would want to do a Sputum Culture, or Tissue/Fluid Sample!!
PPD and IGRA is for Latent TB
Where does TB like to hang out?
- Apices of the lungs
- Posterior section of upper lobe of lung
- Superior section of lower lobe
Can CXRs confirm the dx of TB?
NO
If a patient has HIV (assuming that TB would show up on a CXR) how would TB present on a CXR?
A. The TB will not show up on a CXR in a HIV patient
B. The TB will show up in the “usual” places of the CXR, like the apices of the lung or the posterior section of the upper lobe.
C. The TB will show up in unusual places of the lungs
D. HIV patients cannot contract TB due to developed resistance
C. The TB will show up in unusual places of the lungs
How many sputum samples would you collect in a patient with suspected active TB?
Three
Where does the sputum come from for the samples needed for testing for TB?
- Cough up sputum
- Induced Sputum
- Bronchoscopy
- Gastric Aspiration
What is an AFB smear?
An acid-fast bacillus (AFB) smear is used to look for AFB in a sample from the site of suspected infection. For the smear, the sample is spread thinly onto a glass slide, treated with a special stain, and examined under a microscope. This is a relatively quick way to determine if an infection may be due to one of the acid-fast bacilli, the most common of which is M. tuberculosis.
Other confirmatory mechanism for TB
Molecular PCR
Pro of using AFB smear in dx of TB
Rapid test
Con of using AFB smear in dx of TB
Lacks sensitivity
Pro of using PCR in dx of TB
Sensitive and Specific
Con of using PCR in dx of TB
Not quickly done
Once confirmed, this is the treatment for TB
First 2 months:
- INH 300 mg QD
- RIF 600 mg QD
- PZA 15-30 mg/kg QD
- EMB 12-25 mg/kg QD
- STM 1 gm/d (IM injection)
4 months after, you continue at same dosage
- INH
- RIF
What environments in the body does TB hang out in?
- Intracellular (inside macrophages)
- Extracellular
- Inside granulomas
What could inadequate therapy adherence cause?
- Increased drug resistance
- Incorrect insensitivities
- Malabsorption
- Increased Metabolism
- Inability of drugs to penetrate effected tissues
Big Picture with HIV
At different CD4 levels, the associative pulmonary infections can shift. CD4 levels influence susceptibility of infection
CD4 >400 can cause which Pulmonary Infections
- Sinusitis
- Bronchitis
- Viral URI
- Lung Cancer
CD4 300-399 can cause which Pulmonary Infections
- Bacterial pneumonia
- Pulmonary TB
- Lymphocytic pneumonitis
CD4 200-299 can cause which Pulmonary Infections
- Pulmonary NTMB
- Recurrent Pneumonia
- Lymphoma
CD4 100-199 can cause which Pulmonary Infections
- Bacterial Sepsis
- Disseminated TB
- PCP
- Kaposi’s Sarcoma
CD4 <100 can cause which Pulmonary Infections
- Disseminated MAC/NTMB
- Histoplasmosis
- Cryptococcosis
- CMV Disease
- Coccidiodomycosis
Cause of PCP (Pneumocystis Pneumonia)
Pneumocystis jirovecii (Fungus)
Onset of PCP
Gradual
Symptoms of PCP Pneumonia
- Non-productive cough (95%)
- Fever
- Progressive Dyspnea (95%)
Others:
Fatigue, Chills, Chest Pain, Weight Loss
Imaging suspected PCP
CXR/CT checking for:
- Pneumothoraces
- Lobar or Segmental Infiltrates
- Cysts
- Nodules
- Pleural Effusions
Diagnosis of PCP
- Immunofluorescent staining of specimens obtained by sputum induction is the usual means of making a diagnosis.
- BAL should be performed if induced sputum is negative (IDK what BAL is)
Treatment of PCP
Bactrim, typically 2-3 weeks *no know optimum time”
If allergic to Sulfa: use pentamidine but this drug has serious side effects…so tell your pt to not be allergic, kthanks*
Can be stopped when CD4+ >200 after ART
**Cotreatment of corticosteroid good!
Co-treatment of PCP
Corticosteroids because it reduces the likelihood of respiratory failure, deterioration of oxygenation, and death in pts with moderate-to-severe pneumonia.
When an HIV pt has a CD4 < 50 cell/mL, a common infection would be?
Cytomegalovirus (CMV)
What can CMV cause?
- Retinitis
- Colitis
- Esophagitis
- Gastritis
- Hepatitis
- Encephalitis
- Pneumonia
- Death
CMV most commonly occurs in which patients?
HIV/AIDS
Symptoms of CMV
- Dyspnea
- Non-productive cough
- Fever
- Diffuse Pulmonary Opacities on CXR
Treatment of CMV
IV Gancyclovir or foscarnet
Prognosis of CMV
Long-term is no bueno because of severe immunosuppression
Pathology Slide of CMV
Owl Eyes
Common type of atypical Mycobacterium
MAC (Mycobacterium avium complex)
What does MAC cause?
- Devastating and disseminated complications in the body
2. Death
Symptoms of MAC
- Persistent fevers
- Wasting
- Diarrhea
Most common fungus causing life-threatening illness in patients with AIDS
Cryptococcus neoformans
Most common site of infection for Cryptococcus neoformans
Meninges
CD4 count in Cryptococcus neoformans
<100 cells/mL
Dx of Cryptococcus neoformans
Identification of the organism from sputum, BAL fluid, pleural fluid or lung biopsy specimens
