UNIT 1.2 TB BASIC FACTS AND CLASSIFICATION.pptx

Get the basic facts about TB

1. MODULE 1: UNIT 1.2 TB BASIC FACTS AND CLASSIFICATION IN-SERVICE COURSE IN INTEGRATED AND COMPREHENSIVE TB AND LEPROSY MANAGEMENT

2. Introduction This unit describes basic facts about TB regarding its transmission, risk factors, natural history, TB standard definitions prevention and TB classification.

3. Unit objectives The objective of this unit is to have participants be able to: Describe basic facts about TB (What is TB, characteristics of M. TB, TB transmission, fate of droplet nuclei, TB risk factors, TB natural history and key populations, TB prevention ) Describe standard TB case definitions and TB disease classification

4. What is TB? Tuberculosis (TB) is caused by a bacterium called M ycobacterium tuberculosis ( M.tb ) Other species include: Mycobacterium bovis , Mycobacterium africanum Mycobacterium microti M. tuberculosis causes infection in the lungs or other part of the body. Tubercle bacilli cause lesions in tissues called tubercles .

5. Characteristics of M. tuberculosis Slightly curved rod shaped bacilli Size: 0.2-0.5 microns in diameter, 2-4 microns in length. Have thick cell wall of lipids, waxes and mycolic acids Cell wall protects them from digestion by macrophage enzymes. Cell wall resists decolourization by acid alcohol (retains a red dye) hence name Acid-Alcohol Fast B acilli ( AAFB)

6. Characteristics of M. tuberculosis Multiplies slowly; - every 18-24 hours Can remain dormant for decades Aerobic Non-motile

7. How is TB Transmitted? From person to person by mucous droplets (air borne) when the person with TB of the lungs sneezes, coughs, laughs, spits, sings, talks, breathes Then droplets are inhaled by exposed person into the lungs and deposited into the alveoli. Less frequently transmitted by: Ingestion of Mycobacterium bovis found in unpasteurized milk products Not following recommended safety precautions Airborne TB Transmission

8. Ways through which TB is NOT transmitted Shaking hands with a TB patient Sharing food, sharing cups and plates with a TB patient Touching or sharing towels, bed linen and personal clothes Sharing toilet seat with a TB patient.

9. Number and fate of droplet nuclei Number of TB bacteria carrying droplets < 100 microns in diameter liberated per minute: Speaking/talking 0-210 Coughing 0-3,500 Sneezing 4,500- 1,000,000 Size of the droplets is determined by air velocity Smaller droplets <100 microns are produced at high velocity (e.g a violet sneeze) Source: Duguid 1945

10. Transmission depends on Concentration of TB germs Duration of exposure Ventilation Therefore a close contact of a pulmonary bacteriologically confirmed TB patient who is not on treatment and is living in an environment with poor ventilation is more at risk and is more likely to contract TB than any other person.

11. Risk Factors for TB Infection Being a close contact with a person with active Pulmonary TB (PTB) especially bacteriologically confirmed PTB Close contacts include schools. Living in countries with a high TB burden such as Uganda. High HIV rates in the community because people living with HIV have an increased risk for TB.

12. Risk factors for TB Disease Risk factors for TB Disease Young age (especially less than 2 years), are at the highest risk of TB disease Human Immune Deficiency Virus (HIV) infection, Malnutrition Other Immune-suppressive conditions like post measles disease, severe kidney disease, prolonged use of corticosteroids, and pregnancy. Risk factors for Severity of TB Disease Young age (less than 2 years), HIV infection and lack of BCG vaccination

13. TB Natural history

14. TB Natural history Following TB exposure, only 10% of those exposed to TB become infected And in 90% of those who get infected, immunity develops quickly and body contains the infection hence infection remain latent and may never develop active TB disease.

15. TB Natural history In latent period, the person is not ill, not contagious, has a normal chest x-ray and usually has a positive tuberculin skin test and other newer TB infection tests And the TB bacilli are still alive but surrounded (walled off) by body’s immune system

16. TB natural history Exposure to TB risk factors, e.g. in HIV infection, diabetes mellitus, alcoholism, cancer, and use of immunosuppressive drugs, malnutrition, and advancing age, leads to progression to TB disease In 10% of those infected, the previously dormant germs start multiplying, causing TB disease (Post-primary TB disease) The TB germs may also spread from lymphatic organs and through blood to other parts of the body, a process that takes 6 – 8 weeks. Those who develop TB disease, if untreated die within two years. Only a small proportion of them get self-cured).

17. TB key populations (Most at risk) Immune suppressed individuals HIV positive clients Diabetics Children Occupation exposure Health workers Others Males Congregate settings related Prisoners Refugees and internally displaced Slum dwellers/ urban poor Populations in hard to reach villages, lake showers , Islands and fishing communities Miners and Plantation workers Close contacts of confirmed TB patients Nomadic communities

18. TB prevention BCG vaccination Early detection and treatment of infectious TB patients Isoniazid preventive therapy (IPT) for: All HIV positive persons irrespective of TB exposures Under five-year child contacts of persons with active TB Infection control measures

19. Purpose of TB case definitions and disease classification Uniform criteria to define a TB case are needed for: Proper patient registration and case notification Selecting appropriate TB treatment regimens Standardizing process of data collection for TB control Evaluating the proportion of cases according to site, bacteriology and treatment history Cohort analysis of treatment outcomes Accurate monitoring of trends and evaluation of the effectiveness of TB programs within and across districts, countries and global regions.

20. Standard TB Case Definition Presumptive TB patient : Is any patient who presents with symptoms and signs suggestive of TB (previously called a TB suspect ). Bacteriologically confirmed TB patient (BC) : A bacteriologically confirmed TB patient is one from whom a biological specimen is positive for TB by smear microscopy, culture, Nucleic Acid Amplification Tests e.g. Xpert MTB/RIF or WHO recommend new diagnostics. These Should be recorded in the unit TB register and notified, regardless of whether TB treatment has been started.

21. Standard TB Case Definition Clinically diagnosed TB patient (CD): One who does not fulfil the criteria for bacteriological confirmation but has been diagnosed with active TB by a clinician (doctor, clinical officer, midwife or nurse) has decided to give the patient a full course of TB treatment includes cases diagnosed by X-ray , TB LAM , suggestive histology and extra-pulmonary (EPTB) cases without laboratory confirmation. Clinically diagnosed cases subsequently found to be bacteriologically positive (before or after starting treatment) should be reclassified as bacteriologically confirmed.

22. BC or CD TB cases are also classified according to: A natomical site of the disease (body organ involved) Patient’s history of previous treatment Drug susceptibility and resistance to anti TB medicines and HIV status

23. Classification B ased on Site of the Disease Pulmonary tuberculosis (PTB): Bacteriologically confirmed(BC) or clinically diagnosed (CD) case of TB involving the lung parenchyma or the tracheobronchial tree. Extra-pulmonary tuberculosis (EPTB): any BC or CD case of TB involving organs other than the lungs, e.g. pleura, lymph nodes, abdomen, GIT, skin, joints bones, and meninges. Mediastinal and/or hilar TB or tuberculous pleural effusion, without radiographic abnormalities in the lungs, constitutes a case of extra-pulmonary TB (EPTB). A patient with both pulmonary and extra-pulmonary TB should be classified as a case of PTB.

24. Classification Based on Patient’s History of Previous Treatment New patients : Patients who have never been treated for TB or have taken anti-TB drugs for less than 1 month. Previously treated TB patients : Patients who have received one month or more of anti TB drugs in the past. They are sub classified as follows: Relapse patients: Previously treated for TB, declared cured or treatment completed at the end of their most recent course of treatment, and are now diagnosed with a recurrent episode of TB.

25. Classification Based on Patient’s History of Previous Treatment Treatment after failure patients: are those who have previously been treated for TB and whose treatment failed at the end of their most recent course of treatment. Treatment after loss to follow-up patients: have previously been treated for TB and were declared lost to follow-up at the end of their most recent course of treatment. Other previously treated patients: Previously been treated for TB but whose o utcome after their most recent course of treatment is unknown or undocumented.

26. Classification Based on HIV Infection Status HIV-positive TB patient: any BC or CD case of TB with a positive HIV result from HIV testing conducted at the time of TB diagnosis or other documented evidence of enrolment in HIV care, such as enrolment in the pre-ART register or ART register. HIV-negative TB patient: any BC or CD case of TB who has a negative result from HIV testing conducted at the time of TB diagnosis. Any HIV-negative TB patient subsequently found to be HIV-positive should be reclassified accordingly .

27. Classification Based on Drug susceptibility to anti TB medicines Drug Susceptible TB: The MTB germs are susceptible to FLD anti TB drugs (RHZE) Drug Resistant TB: The MTB germs are resistant to one or more FLD (RHZE) and SLD (Kanamycin (km), Capreomycin, Levofloxacin, Ethionamide, Prothionamide , etc )

28. Classification Based on Drug Resistance Mono resistance: resistance to one first-line anti-TB drug only. Poly drug resistance: resistance to more than one first-line anti-TB drug (other than both Isoniazid and Rifampicin). Multidrug resistance (MDR): resistance to at least both Isoniazid and Rifampicin Extensive drug resistance (XDR): resistance to any Fluoroquinolone and to at least one of three second-line injectable drugs (Capreomycin, Kanamycin and Amikacin ), in addition to multidrug resistance.

29. Classification Based on Drug Resistance Rifampicin resistance (RR) : Resistance to Rifampicin detected using phenotypic (usual drug susceptibility testing, DST) or genotypic methods (commonly Xpert MTB/Rif), with or without resistance to other anti-TB drugs. It includes any resistance to Rifampicin, whether mono, poly, multi, or extensively drug resistance. These categories are not all mutually exclusive; when enumerating Rifampicin resistant TB (RR-TB), for instance, multi-drug TB (MDR-TB), and Extensively drug resistance (XDR-TB) are also included.

30. Classification Based on Drug Resistance “ Pre-XDR” TB : refers to an isolate that is resistant to either a fluoroquinolone or a second-line injectable, but not both. It is a commonly used designation but not officially accepted terminology by WHO or the global TB community.

31. Group Exercise Working in small groups, answer the following questions: How is TB classified? What is the importance of TB case definitions and TB disease classification?

32. Conclusion Tuberculosis (TB) is caused by a bacterium called Mycobacterium tuberculosis ( M.tb ) It is an Acid-Alcohol fast bacillus ( AAFB) TB is an air borne disease transmitted when the person with TB of the lungs sneezes, coughs, laughs, spits, sings, talks, breathes Transmission depends on concentration of TB germs, duration of exposure and ventilation TB Classification is based on anatomical site of the disease, patient’s history of previous treatment, susceptibility to anti TB medicines and HIV status

33. References World Health Organization. Global tuberculosis report 2015. Manual of the National Tuberculosis and Leprosy program, Uganda. 3 nd Edition 2017 Richeldi L. An Update on the Diagnosis of Tuberculosis Infection. Am J Respir Crit Care Med. 2006; 174:736-742