FundamentalsofTB.ppt
- 2. 2 TB in the United States • From 1953 to 1984, reported cases decreased by approximately 5.6% each year • From 1985 to 1992, reported cases increased by 20% • 25,313 cases reported in 1993 • Since 1993, cases are steadily declining
- 3. 3 Factors Contributing to the Increase in TB Cases • HIV epidemic • Increased immigration from high- prevalence countries • Transmission of TB in congregate settings (e.g., correctional facilities, long term care) • Deterioration of the public health care infrastructure
- 4. 4 Transmission and Pathogenesis of TB • Caused by Mycobacterium tuberculosis (M. tuberculosis) • Spread person to person through airborne particles that contain M. tuberculosis, called droplet nuclei • Transmission occurs when an infectious person coughs, sneezes, laughs, or sings • Prolonged contact needed for transmission • 10% of infected persons will develop TB disease at some point in their lives
- 5. 5 Sites of TB Disease • Pulmonary TB occurs in the lungs – 85% of all TB cases are pulmonary • Extrapulmonary TB occurs in places other than the lungs, including the: – Larynx – Lymph nodes – Brain and spine – Kidneys – Bones and joints • Miliary TB occurs when tubercle bacilli enter the bloodstream and are carried to all parts of the body
- 6. 6 Not Everyone Exposed Becomes Infected • Probability of transmission depends on: – Infectiousness – Type of environment – Length of exposure • 10% of infected persons will develop TB disease at some point in their lives – 5% within 1-2 years – 5% at some point in their lives
- 7. 7 Persons at Risk for Developing TB Disease • Persons at high risk for developing TB disease fall into 2 categories – Those who have been recently infected – Those with clinical conditions that increase their risk of progressing from LTBI to TB disease
- 8. 8 Recent Infection as a Risk Factor Persons more likely to have been recently infected include • Close contacts to persons with infectious TB • Skin test converters (within past 2 years) • Recent immigrants from TB-endemic areas (within 5 years of arrival to the U.S.) • Children ≤ 5 years with a positive TST • Residents and employees of high-risk congregate settings (e.g. correctional facilities, homeless shelters, healthcare facilities)
- 9. 9 Increased Risk for Progression to TB Disease Persons more likely to progress from LTBI to TB disease include • HIV infected persons • Those with history of prior, untreated TB • Underweight or malnourished persons • Injection drug use • Those receiving TNF-α antagonists for treatment of rheumatoid arthritis or Crohn’s disease • Certain medical conditions
- 10. 10 Latent TB Infection (LTBI) • Occurs when person breathes in bacteria and it reaches the air sacs (alveoli) of lung • Immune system keeps bacilli contained and under control • Person is not infectious and has no symptoms
- 11. 11 TB Disease • Occurs when immune system cannot keep bacilli contained • Bacilli begin to multiply rapidly • Person develops TB symptoms
- 12. 12 LTBI vs. TB Disease LTBI TB Disease Tubercle bacilli in the body TST or QFT-Gold® result usually positive Chest x-ray usually normal Chest x-ray usually abnormal Sputum smears and cultures negative Symptoms smears and cultures positive No symptoms Symptoms such as cough, fever, weight, loss Not infectious Often infectious before treatment Not a case of TB A case of TB
- 13. 13 Targeted Testing • Detects persons with LTBI who would benefit from treatment • De-emphasize testing of groups of people who are not at risk (mass screening) • Consider using a risk assessment tool • Testing should be done only if there is an intent to treat • Can help reduce the waste of resources and prevent unnecessary treatment
- 14. 14 Groups to Target with the Tuberculin Skin Test • Persons with or at risk for HIV infection • Close contacts of persons with infectious TB • Persons with certain medical conditions • Injection drug users • Foreign-born persons from areas where TB is common • Medically underserved, low-income populations • Residents of high-risk congregate settings • Locally identified high-prevalence groups
- 15. 15 Administering the TST • Use Mantoux tuberculin skin test • 0.1 mL of 5-TU of purified protein derivative (PPD) solution injected intradermally • Use a 27 gauge needle • Produce a wheal that is 6-10mm in diameter
- 16. 16 Reading the TST • Read within 48-72 hours • Measure induration, not erythema • Positive reactions can be measured accurately for up to 7 days • Negative reactions can be read accurately for only 72 hours
- 17. 17 TST Interpretation - 1 5 mm of induration is positive in: – HIV-infected persons – Close contacts to an infectious TB case – Persons who have chest x-ray findings consistent with prior untreated TB – Organ transplant recipients – Persons who are immunosuppressed (e.g., those taking the equivalent of >15 mg/d of prednisone for 1 month or those taking TNF-α antagonists)
- 18. 18 TST Interpretation - 2 10 mm induration is positive in: – Recent immigrants (within last 5 years) from a high-prevalence country – Injection drug users – Persons with other high-risk medical conditions – Residents or employees of high-risk congregate settings – Mycobacteriology laboratory personnel – Children < 4 years of age; infants, children, and adolescents exposed to adults at high risk
- 19. 19 TST Interpretation - 3 15 mm induration is positive in: • Persons with no known risk factors for TB
- 20. 20 Recording TST Results • Record results in millimeters of induration, not “negative” or “positive” • Only trained healthcare professionals should read and interpret TST results
- 21. 21 False Positive TST Reactions • Nontuberculous mycobacteria – Reactions are usually ≤10mm of induration • BCG vaccination – Reactivity in BCG vaccine recipients generally wanes over time – Positive TST results is likely due to TB infection if risk factors are present – BCG-vaccinated persons with positive TST result should be evaluated for treatment of LTBI – QFT is able to distinguish M.tb from other mycobacteria and BCG vaccine
- 22. 22 False Negative TST Reactions • Anergy, or inability to react to TST because of weakened immune system • Recent TB infection (2-10 weeks after exposure) • Very young age (newborns) • Recent live-virus vaccination can temporarily suppress TST reactivity • Poor TST administration technique (too shallow or too deep, or wheal is too small)
- 23. 23 Boosting • Some people with history of LTBI lose their ability to react to tuberculin (immune system “forgets” how to react to TB-like substance, i.e., PPD) • Initial TST may stimulate (boost) the ability to react to tuberculin • Positive reactions to subsequent tests may be misinterpreted as new infections rather than “boosted” reactions
- 24. 24 Two-Step Testing - 1 • A strategy for differentiating between boosted reactions and reactions caused by recent TB infection • Use two-step testing for initial (baseline) skin testing of adults who will be re-tested periodically • 2nd skin test given 1-3 weeks after baseline
- 25. 25 Two-Step Testing - 2 • If the 1st TST is positive, consider the person infected • If the 1st TST is negative, administer 2nd TST in 1-3 weeks • If the 2nd TST is positive, consider the person infected • If the 2nd TST is negative, consider the person uninfected at baseline
- 26. 26 Infectiousness - 1 • Patients should be considered infectious if they: – Are undergoing cough-inducing procedures – Have sputum smears positive for acid-fast bacilli (AFB) and: • Are not receiving treatment • Have just started treatment, or • Have a poor clinical or bacterial response to treatment – Have cavitary disease • Extrapulmonary TB patients are not infectious
- 27. 27 Infectiousness - 2 • Patients are not considered infectious if they meet all these criteria: – Received adequate treatment for 2-3 weeks – Favorable clinical response to treatment – 3 consecutive negative sputum smears results from sputum collected on different days
- 28. 28 Techniques to Decrease TB Transmission • Instruct patient to: – Cover mouth when coughing or sneezing – Wear mask as instructed – Open windows to assure proper ventilation – Do not go to work or school until instructed by physician – Avoid public places – Limit visitors – Maintain home or hospital isolation as ordered
- 29. 29 Evaluation for TB • Medical history • Physical examination • Mantoux tuberculin skin test • Chest x-ray • Bacteriologic exam (smear and culture)
- 30. 30 Symptoms of TB • Productive prolonged cough* • Chest pain* • Hemoptysis* • Fever and chills • Night sweats • Fatigue • Loss of appetite • Weight loss *Commonly seen in cases of pulmonary TB
- 31. 31 Chest x-Ray • Obtain chest x-ray for patients with positive TST results or with symptoms suggestive of TB • Abnormal chest x-ray, by itself, cannot confirm the diagnosis of TB but can be used in conjunction with other diagnostic indicators
- 32. 32 Sputum Collection • Sputum specimens are essential to confirm TB – Specimens should be from lung secretions, not saliva • Collect 3 specimens on 3 different days • Spontaneous morning sputum more desirable than induced specimens • Collect sputum before treatment is initiated
- 33. 33 Smear Examination • Strongly consider TB in patients with smears containing acid-fast bacilli (AFB) • Use subsequent smear examinations to assess patient’s infectiousness and response to treatment
- 34. 34 Culture • Used to confirm diagnosis of TB • Culture all specimens, even if smear is negative • Initial drug isolate should be used to determine drug susceptibility
- 35. 35 Treatment of Latent TB Infection • Daily Isoniazid therapy for 9 months – Monitor patients for signs and symptoms of hepatitis and peripheral neuropathy • Alternate regimen – Rifampin for 4 months
- 36. 36 Treatment of TB Disease • Include four 1st-line drugs in initial regimen – Isoniazid (INH) – Rifampin (RIF) – Pyrazinamide (PZA) – Ethambutol (EMB) • Adjust regimen when drug susceptibility results become available or if patient has difficulty with any of the medications • Never add a single drug to a failing regimen • Promote adherence and ensure treatment completion
- 37. 37 Directly Observed Therapy (DOT) • Health care worker watches patient swallow each dose of medication • DOT is the best way to ensure adherence • Should be used with all intermittent regimens • Reduces relapse of TB disease and acquired drug resistance
- 38. 38 Clinical Monitoring Instruct patients taking TB medications to immediately report the following: – Rash – Nausea, loss of appetite, vomiting, abdominal pain – Persistently dark urine – Fatigue or weakness – Persistent numbness in hands or feet
- 39. 39 Drug Resistance • Primary - infection with a strain of M. tuberculosis that is already resistant to one or more drugs • Acquired - infection with a strain of M. tuberculosis that becomes drug resistant due to inappropriate or inadequate treatment
- 40. 40 Barriers to Adherence • Stigma • Extensive duration of treatment • Adverse reactions to medications • Concerns of toxicity • Lack of knowledge about TB and its treatment
- 41. 41 Improving Adherence • Adherence is the responsibility of the provider, not the patient and can be ensured by: – Patient education – Directly observed therapy (DOT) – Case management – Incentives/enablers
- 42. 42 Measures to Promote Adherence • Develop an individualized treatment plan for each patient • Provide culturally and linguistically appropriate care to patient • Educate patient about TB, medication dosage, and possible adverse reactions • Use incentives and enablers to address barriers • Facilitate access to health and social services
- 43. 43 Completion of Therapy • Based on total number of doses administered, not duration of treatment • Extend or re-start if there were frequent or prolonged interruptions
- 44. 44 Meeting the Challenge • Prevent TB by assessing risk factors • If risk is present, perform TST • If TST is positive, rule out active disease • If active disease is ruled out, initiate treatment for LTBI • If treatment is initiated, ensure completion
- 45. 45 Remember “A decision to test is a decision to treat.”