WEEK 1: Tuberculosis and Public Health Flashcards
Outline risk factors for TB.
*Extremes of age
* HIV
* Under nutrition
* Contacts of people known or suspected to have TB disease
* People who live in, or have lived in, high-risk congregate settings (for example
correctional facilities)
* Populations defined locally as having an increased incidence of LTBI or TB disease,
* Medically underserved, low-income populations, or persons who abuse drugs or
alcohol
Outline the NON- Bacteriological tools for TB diagnosis.
*Symptom screening
*Mantoux/ PPD / TST
*Chest x-ray
*Diagnostic algorithm
Outline challenges of NON- Bacteriological tools for TB diagnosis.
*Some symptoms are not specific for TB e.g., fever
*Require training of health care worker e.g., X-rays reading and interpretation
*Often misses extra-pulmonary TB.
*Sensitivity and Specificity: Non-bacteriological tests may lack sensitivity and specificity compared to traditional bacteriological methods, such as sputum smear microscopy or culture. This can lead to false-negative or false-positive results, potentially resulting in missed diagnoses or unnecessary treatment.
Outline bacteriological tests for TB.
BACTERIOLOGICAL TESTS
* Smear microscopy
* GeneXpert
* Culture
* Urine LAM
Discuss sputum smear microscopy.
Outline it disadvantages.
Sputum smear microscopy remains the cornerstone of TB diagnosis in developing countries.
* The method depends upon the quality and bacterial load of the sputum specimen and the training and motivation of laboratory technicians.
DISADVANTAGES
* Although highly specific in most countries, smear
microscopy is insensitive – it detects roughly 50% of all the active cases of TB.
* Sensitivity can be as low as 20% in children and HIV infected people.
*Furthermore, smear microscopy cannot detect resistance to drugs.
* A person with suspected TB typically has to visit the
clinic at least twice before a diagnosis can be made,
and then has to return again for the results.
* This process can be expensive in terms of
transportation costs and lost wages from time off
work. Some people never complete the testing process, or do not return for their results.
*Cannot detect EPTB.
Discuss Culture test for TB.
State its disadvantages.
Culture of TB bacteria on liquid or solid media is a more sensitive method for TB diagnosis than smear microscopy and it permits testing for drug resistance.
- TB culture has limitations, however: it requires biosafety facilities that are expensive to build and maintain and specially trained laboratory technicians to perform the procedure.
* Some national TB programmes in developing countries have no functioning TB culture facility at all.
TB culture is performed only at national reference laboratories or in hospital laboratories in large cities. - Few developing countries have capacity for good-quality drug-susceptibility testing (DST) for first-line drugs and even fewer have the capacity to test for second-line drug resistance.
- Even where capacity exists, diagnosing TB with culture takes weeks because of the slow growth rate of TB bacilli.
* Specimens are often sent to distant laboratories. This can delay processing.
* Furthermore, test results must travel long distances back to reach the clinic and the patient.
Discuss GeneXpert MTB device.
State its potential advantages.
Outline the disadvantages.
The Xpert MTB device is a fully automated system that allows a relatively untrained operator to perform sample processing, DNA amplification, and
detection of M. tuberculosis and screening for rifampin resistance in less than 2 hours and only minutes of hands-on time.
Potential advantages:
* Results can be available while patient waits in clinic.
* The test detects TB in essentially all smear-positive samples and the majority of smear-negative samples.
* The presence of non-tuberculous mycobacteria
* The cartridges are stable at room temperature.
* Same device may be used for HIV viral load detection and HPV.
DISADVANTAGES
* Computer-driven, sophisticated piece of equipment that will require reliable energy supply, security and maintenance.
* Laboratories performing the Xpert MTB assay will require BSL-1 laboratory infrastructure and equipment.
* Technicians require training in BSL-1 safety precautions and the use of the GeneXpert device.
* A reliable source of electricity is needed as well as a room that can be secured outside working hours.
Discuss Mycobacterial lipoarabinomannan (LAM) antigen Urine test.
- Tests based on the detection of mycobacterial lipoarabinomannan (LAM) antigen in urine have emerged as a potential point-of-care test
for tuberculosis (TB). Owing to suboptimal sensitivity, the urinary LAM assays are unsuitable as general screening tests for TB. - However, unlike traditional diagnostic methods, they demonstrate improved sensitivity for the diagnosis of TB among individuals coinfected with HIV which further increases in patients with low CD4
counts. - Rule-in test for TB in patients with advanced HIV-induced immunosuppression and facilitate the early initiation of antituberculosis treatment.
Describe the aim of primary and secondary prevention.
PRIMARY: Blocks infection
SECONDARY: Block the conversion of latent infection to active TB.
Outline different ways of TB prevention.
*Early diagnosis and effective treatment of infectious people.
*Good infection control: Open windows, cover mouth when coughing, social distancing, etc.
*Isoniazid prevention therapy
*Better housing (well ventilated, not overcrowded)
*Good nutrition
*ART adherence
*Screen health care workers for TB
*Health care workers to wear face masks.
Discuss contact investigation.
Tuberculosis (TB) contacts are people who have close contact with patients with infectious TB.
* As they are at high risk for infection (and in line with the End TB strategy), TB contacts should be investigated systematically and actively for TB infection and disease.
Outline the IMPORTANCE OF CONTACT INVESTIGATION.
- Contribute to early identification of active TB, thus
decreasing its severity and reducing transmission of
Mycobacterium tuberculosis to others, and identification of latent TB infection (LTBI), to allow preventive measures. - Early identification means a better chance of cure and, especially, a reduction in further transmission. Furthermore, contact investigation allows identification of people who are latently infected and at high risk for active TB, who can be treated preventively.
- Many studies in countries with a high TB incidence have shown that the prevalence may reach 5% or more among contacts, particularly among household members.
- Other data suggest that contact investigations could be particularly useful for identifying childhood TB.
- Furthermore, contact investigation can help identify people who require careful follow-up, such as those who were exposed to an index case of multi-drug-resistant or extensively drug-resistant TB or people infected with HIV, whose risk for rapid progression to active TB is very high.
