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TB Case Definitions and Categorizations for Effective Treatment

Learn the importance of defining and categorizing TB cases for proper registration, treatment selection, and program evaluation. Understand World Health Organization case definitions and classifications, including anatomical sites, bacteriologic results, and HIV status.

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TB Case Definitions and Categorizations for Effective Treatment

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  1. Module 4 – March 2010 World Health Organization TB Case Definitions

  2. Project Partners Funded by the Health Resources and Services Administration (HRSA)

  3. Module Overview • TB Case Definitions • Categories for Classifying TB Cases • Site of Disease • Bacteriologic Result • HIV Status • History of Prior Treatment • TB Case Registration Groups

  4. Learning Objectives Objectives: At the end of this presentation, participants will be able to: • Define TB cases utilizing the World Health Organization case definitions for tuberculosis • State the four key features important to classifying TB cases • Categorize TB cases utilizing the World Health Organization registration groupings

  5. TB Case Definitions

  6. Why do we define and categorize TB cases?

  7. Purpose of TB Case Definitions • Correct categorization of patients before starting treatment for TB is essential: • for proper patient registration and case notification • to select the appropriate treatment regimen • to standardize the process of data collection for TB control • to evaluate the proportion of cases according to site, bacteriology, and treatment history • for cohort analysis of treatment outcomes • to accurately monitor trends and evaluate the effectiveness of TB programs

  8. TB Case Definitions • Tuberculosis suspect — Any person who presents with symptoms or signs suggestive of TB (e.g., a cough of long duration, > 2 weeks) • Case of tuberculosis • a definite case of TB (defined next slide) or • diagnosed by a health worker with the plan to treat with a full course of anti-TB treatment Any person started on TB treatment should be recorded as a case. Incomplete “trial” TB treatment should not be given as a method for diagnosis

  9. TB Case Definitions (2) • Definite case of tuberculosis: A patient with M. tuberculosis complex identified from a clinical specimen by culture or newer method (e.g., nucleic acid amplification, molecular beacon or line probe assays) In countries where M. tuberculosis cannot routinely be identified, a pulmonary case with one or more initial sputum smears positive for acid-fast bacilli (AFB) is also considered a “definite” case

  10. Categories for Classifying TB Cases

  11. TB Case Classifications TB cases are also classified according to: • Anatomical site of TB disease • Bacteriologic results (including drug resistance) • History of previous TB treatment • HIV status of the patient

  12. Anatomical Site of Disease • Pulmonary Tuberculosis (PTB): Refers to disease involving the lung parenchyma • A patient with both pulmonary and extra-pulmonary TB constitutes a case of PTB • Miliary TB is classified as PTB because there are lesions in the lungs

  13. Anatomical Site of Disease (2) • Extra-pulmonary Tuberculosis (EPTB): Refers to TB disease of organs other than the lungs. Therefore the following constitute a case of EPTB: • Tuberculous intrathoracic lymphadenopathy (mediastinal and/or hilar) • Tuberculous pleural effusion, without radiographic abnormalities in the lungs • Extrathoracic TB

  14. Anatomical Site of Disease (3) • Diagnosis of EPTB should be based on a decision to treat with a full course along with: • One culture-positive specimen; or • Histological specimen; or • Strong clinical evidence consistent with active EPTB and a decision to treat with a full course of anti-TB treatment • Where several EPTB sites are involved, the case definition depends on the site representing the most severe form of disease • Classify as PTB if both pulmonary and extra-pulmonary sites involved

  15. Bacteriologic Result • Includes smear, culture and newer methods for identification of M. tuberculosis • Defining the AFB smear result is important : • to identify smear-positive cases = most infectious; most likely to transmit TB to others • to identify sputum smear-negative cases, especially HIV positive persons • to record, report, and evaluate program performance Bacteriologic monitoring for treatment response is most practical in smear-positive patients

  16. Bacteriologic Result (2) Pulmonary TB: Sputum smear-positive • Where there is a functional EQA system: • A patient with one or more sputum specimens that are AFB smear-positive is considered a PTB case

  17. Bacteriologic Result (2) Pulmonary TB: Sputum smear-positive • Where there is not yet a functional EQA system, then one of the following apply at treatment start: • > 2 sputum specimens are AFB smear-positive; or • at least 1 sputum specimen is AFB smear-positive and radiographic abnormalities consistent with active PTB are present and determined by a clinician; or • at least one sputum specimen is AFB smear-positive plus culture is positive for M. tb

  18. Bacteriologic Result (3) Pulmonary TB: Sputum smear-negative • At least 2 sputum specimens are negative for AFB at start of treatment • No specimen is smear positive • Obtain TB culture for all smear-negative cases

  19. Bacteriologic Result (4) Pulmonary TB: Sputum smear-negative Defined as: • Smear-negative but culture-positive for M.tb; or • Meet the following criteria: • decision by a clinician to treat with a full course of anti-tuberculosis chemotherapy, and • radiographic abnormalities consistent with active PTB, and either: • laboratory or strong clinical evidence of HIV infection or • no response to a course of broad-spectrum non-TB antibiotics (if HIV-negative or status unknown)

  20. Bacteriologic Result (5) Pulmonary TB: Smear not done • PTB cases without smear results are no longer classified as smear-negative! • Classify as “smear not done” on the TB Register and annual survey

  21. Bacteriologic Result (6) ISTC Standard 3: Extrapulmonary Specimens For all patients suspected of having extrapulmonary TB, appropriate specimens from the suspected sites of involvement should be obtained for microscopy, culture and histopathological examination. International Standards for Tuberculosis Care, 2009

  22. HIV Status • Determining and recording HIV status for TB cases is critical for: • Making treatment decisions • Monitoring trends • Assessing program performance • The 2006 updated TB Register and TB Treatment Card include dates for: • HIV testing • Co-trimoxazole initiation • ART initiation

  23. History of Previous TB Treatment • A case should be defined according to whether or not the patient has previously received TB treatment in order to: • Identify patients at increased risk of acquired drug resistance • Provide epidemiological monitoring of the TB epidemic and program performance at regional and country levels

  24. TB Case Registration Groups

  25. TB Case Registration Groups • New case: A patient who has never had treatment for TB or who has taken anti-tuberculosis drugs for less than 1 month • Previously Treated case: A patient who has received a month or more of anti-TB drugs in the past (with positive or negative bacteriology) • Case is further classified by outcome of most recent course of treatment  No “chronic” category

  26. TB Case Registration Groups (2) Previously treated cases • Relapse: A patient previously treated for TB who has been declared cured or treatment completed, and is diagnosed with bacteriologically positive TB (smear, culture or newer means of identifying M.tb) • Treatment after Failure: A patient who is started on a re-treatment regimen after having failed previous treatment • Treatment after Default: A patient who returns to treatment following interruption of treatment for > 1 month and is positive bacteriologically

  27. TB Case Registration Groups (3) • Transfer in: A patient who has transferred from another TB register to continue treatment • Other: All cases that do not fit the previous definitions. This includes: • Previous treatment history is unknown • Previously treated, but outcome is unknown • Returned to treatment with: • smear-negative PTB • bacteriologically negative EPTB

  28. TB Case Registration Activity

  29. Summary • Every TB patient should be assessed for the four key features of case definition so they can be classified correctly and begin treatment • Every TB patient should have TB case registration group determined prior to initiation of TB treatment

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