Tuberculosis pathophysiology and diagnosis | Jindal Chest Clinic

Tuberculosis is an infectious lung disease caused by bacteria, spreading through the air through coughing, sneezing, or spit. It is preventable and curable. This presentation gives an overview on "Tuberculosis pathophysiology and diagnosis". For more information, please contact us: 9779030507.

1. Tuberculosis Pathophysiology and diagnosis Dr . Aditya Jindal Interventional Pulmonologist & Intensivist Jindal Clinics SCO 21, Sec 20D, Chandigarh DM Pulmonary and Critical Care Medicine (PGI Chandigarh ), FCCP

2. Course of TB infection

3. Types of TB Primary tuberculosis is a form of disease that develops in a previously unexposed and therefore unsensitized person Secondary tuberculosis is the pattern of disease that arises in previously sensitized or infected host.

4. Primary TB Infection of an individual who has not been previously infected or immunized. The inhaled bacilli implant in the distal airspaces of lower part of upper lobe or upper part of lower lobe close to the pleura As sensitization develops, a gray-white inflammatory consolidation is formed  Ghon focus

5. Sites of Primary TB Most common - Lungs Other sites: Tonsils, adenoids Site of BCG vaccination GIT – ileum, colon etc GUT

6. Ghon’s complex Consists of 2 components Pulmonary component lesion in the lung ( Ghon focus or primary focus) 1-2cm solitary area located peripherally in the subpleural focus in the lower part of upper lobe or upper part of lower lobe Micro: the lung lesion show tuberculous granuloma with caseous necrosis Lymphatic component lymphatics draining lung lesion containing phagocytes with M. tuberculosis bacilli

7. Ghon complex

8. Fate of Primary complex Heal by fibrosis  calcification Progressive primary tuberculosis Primary miliary tuberculosis

9. Secondary TB The infection of an individual who has been previously infected or sensitized The infection may be acquired from Endogenous source  reactivation of dormant primary complex Exogenous source

10. Pathological lesions of Secondary TB The initial lesion is a small focus of consolidation of <2cm in diameter within 1 to 2cm of apical pleura Gross: sharply circumscribed, firm, gray white to yellow with variable amount of central caseation necrosis Micro: coalescent tuberculous granulomas with central caseation necrosis.

11. Fate of secondary TB The lesion may heal with fibrous scarring and calcification Fibrocaseous tuberculosis (progressive pulmonary TB ) Tuberculous caseous pneumonia Miliary tuberculosis

12. Pathology of TB Granuloma formation is the hall-mark of pathology of TB Granuloma is a: i. Rounded tight collection of chronic inflammatory cells ii. Central Caseous necrosis iii. Active macrophages - epithelioid cells iv. Outer layer of lymphocytes & fibroblasts v. Langhans giant cells – joined epithelioid cells

13. TB Pathology Bacterial entry T Lymphocytes. Macrophages. Epithelioid cells. Proliferation. Central Necrosis. Giant cell formation. Fibrosis.

14. Granuloma Histopathology

15. Caseation necrosis

16. Causes of granuloma formation Tuberculosis Other mycobacterial infections, Leprosy Bacterial infections: Brucellosis Other infections: Fungal, viral, protozoal Non-infectious causes - Sarcoidosis - Foreign bodies - Lymphomas

17. Miliary TB Occurs when organisms drain through lymphatics into  lymphatic ducts venous return on the right side of heart pulmonary arteries Individual lesions are either microscopic or small, visible (2mm) foci of yellow-white consolidation scattered through the lung parenchyma (resembling millet seeds ) Micro: the lesion shows structure of granuloma with minute areas of caseous necrosis.

18. Miliary TB

19. Course of TB infection

20. Tuberculosis Diagnosis

21. Clinical Features Sputum Examination Chest Radiology Bronchoscopy Mantoux test Indirect laboratory tests

22. Clinical Symptoms Prolonged fever, malaise, weakness, wt. loss etc. Pulmonary: Cough, sputum, haemoptysis – persistent Lymphadenopathy, organ enlargement, others

23. Clinical Features Sputum Examination Mantoux test Chest Radiology Bronchoscopy Indirect laboratory tests

24. Sputum examination Smear examination (Sputum, other secretions) Auramine - Rhodamine staining Culture of material/ tissues

25. Myco -bacteria Myco (fungus like) Bacterium (bacteria) Ability to resist decolourization by a weak mineral acid after staining with an aryl-methane dyes (acid-fastness) Slender, straight or slightly curved, rod shaped Length 2-4 u, Breadth 0.2-0.8 u Occur singly, in pairs or small groups Long, filamentous, club-shaped (rarely branching)

26. MYCOBACTERIAL DEMONSTRATION Smear: Easiest, quickest Requires > 10000 AFB/ml Sensitivity 50-60%; Specificity: High Culture: More sensitive; 10 AFB/ml Traditional 6-8 wks Septi Chek : Biphasic; High yield Radiometric: BACTEC Others: Animal pathogenicity Antimicrobial sensitivity

27. M tb in sputum smear

28. Rapid culture methods BACTEC system MycobactGrowth Indicator Tube(MGIT) MB/ BacT system Septi-chek ESP culture system Microscopic observation of broth/slide cultures

29. M tb Colonies on culture (LJ medium)

30. BACTEC System Radiometric method 14C labelled palmitic acid added to liquid 7H12 medium Detects MTB by metabolism rather than growth 14CO 2 produced detected Growth index(GI) measured Results available in 7-14 days (87-96%)

31. MGIT Automated system Capable of analyzing 960 specimens Metabolism of MTB produces O2 Fluorescence of dye with oxygen measured Results available in 7-14 days Cost effective for high load micro labs

32. Clinical Features Sputum Examination Chest Radiology Bronchoscopy Mantoux test Indirect laboratory tests

33. Chest radiology I. Chest: Upper Lobes/Diffuse miliary Infiltrates/Exudates/Fibrosis Multiple, thin walled cavities Lymphadenopathy, Pl.effusion II. Others : Enlargement of organs Erosions/Effusions Caseations /collections

34. Role of Chest X-ray No chest X-ray pattern is absolutely typical of TB 10-15% of culture-positive TB patients not diagnosed by X-ray 40 % of patients diagnosed as having TB on the basis of x-ray alone do not have active TB X-ray is unreliable for diagnosing and monitoring treatment of tuberculosis

35. Clinical Features Sputum Examination Chest Radiology Bronchoscopy Mantoux test Indirect laboratory tests

36. Role of bronchoscopy Valuable in early diagnosis of strongly suspected sputum-negative TB Diagnosis of endobronchial TB/ miliary TB TBLB yield is greater (82%) than BAL (26 %) TBNA has a role in mediastinal lymph nodal tuberculosis with negative sputum smears

37. ESR? NO ROLE IN DIAGNOSIS

38. Clinical Features Sputum Examination Chest Radiology Bronchoscopy Mantoux test Indirect laboratory tests

39. Tuberculin ( Mantoux ) Test Infection with mycobacterium tuberculosis leads to delayed hypersensitivity reaction which can be detected by Mantoux test About 2 to 4 weeks after infection I ntracutaneous injection of purified protein derivative (PPD) of M.tuberculosis Induces a visible and palpable induration that peaks in 48 to 72 hours

40. How to do the test? Sub cutaneous Weal formation Itching – no scratch Read after 72 hours Induration size . 5-10-15mm

41. Positive test

42. Interpretation Induration less than 5 mm –> no exposure to tubercular bacilli Induration between 5-9 mm –> this can be due to atypical mycobacteria or BCG vaccination. It may suggest infection in immunocompromised children such as HIV infection or other immunosuppression Induation 10 mm or more –> in a child with symptoms of tuberculosis should be interpreted as tubercular disease

43. Clinical significance Denotes infection Does not differentiate infection from active disease A strongly positive Mantoux can support a clinical diagnosis Better negative than positive predictive value Cut-off for a positive test?

44. Clinical Features Sputum Examination Chest Radiology Bronchoscopy Mantoux test Indirect laboratory tests

45. Indirect Tests Biochemical tests LDH , Proteins Adenosine Deaminase Bromide Partition Test Gas Chromatography – Fatty acids, alcohols etc Immuno-diagnosis tests Skin test ( Mantoux ) Detection of Antibodies (Tests banned ) Genetic/ molecular studies Antigen detection Lipo arabinomannan Nucleic Acid Probes Ligase Chain Reaction Polymerase Chain Reaction Gene Xpert

46. Serological Tests Low turn around time Limitation Low sensitivity in s mear negative patients HIV positive cases, In disease -endemic countries with a high infection rate Poor standardization Banned in 2012.

47. Interferon- γ release assays An alternative to the TST in the form of a new type of in-vitro T-cell-based assay (Test-tube TST) Gold IGRA Elispot T test T cells of individuals sensitized with tuberculosis antigens produce interferon- γ when they re-encounter mycobacterial antigens High level of interferon- γ production - presumptive of tuberculosis infection

48. IGRA in LTBI In the absence of a gold standard for diagnosis of Latent TBI, the sensitivity and specificity cannot be directly estimated IGRA have higher specificity than TST Better correlation with surrogate markers of exposure to M tuberculosis ( in low-incidence setting countries ) Less cross reactivity as a result of BCG vaccination than TST

49. PCR Synthesis of dsDNA by hybridization of oligonucleotides to targets s-DNA Uses thermal cycler to denature the target DNA Thermostable polymerase for DNA amplification Repeated cycles by varying temp for primer annealing (70-72 C) and denaturation (94-96 C) Amplified product are then detected by southern blotting and fluorescent/radiolabelled probes hybridization

50. Gene X-pert Test Detection and identification of mycobacteria directly from clinical samples Uses real‐time polymerase‐chain reaction ( PCR) assay to amplify an MTB‐specific sequence of the rpoB gene Cartridge based, PCR test for detection of mycobacteria and Rifampicin resistance Rapid test. Results within hours . Costly Continuous electric supply and temperature maintenance ? Field feasibility, sensitivity and specificity in India

51. I ntegrates sample processing and PCR Reagents required for bacterial lysis, nucleic acid extraction, amplification and amplicon detection are present in a disposable plastic cartridge Only manual step ‐‐ addition of a bactericidal buffer to sputum before transferring a defined volume to the cartridge MTB/RIF cartridge is then inserted into the GeneXpert device R esults within 2 hours

52. Diagnosis of Extra Pulmonary TB Sputum or other smears are often Negative These are difficult to use for diagnosis and start of treatment Follow up Monitoring End point Recurrence / Relapse Mostly clinico -radio- histo /cytological Invasive procedures frequently required to obtain tissue, fluids, etc. to look for T.b . and/or histo -cytological criteria.

53. Difficulties of specimens testing for EPTB Specimen Relevance of a particular sample Method of collection Contamination/ inappropriate site Processing Technique , Standardization and calibration of Instrument/procedure Clinical interpretation Disease ?

54. How to confirm the Diagnosis? LEVELS OF DIAGNOSIS OF TB Suggestive Clinical/Epidemiological Radiological Presumptive/Possible Therapeutic response Immunological Markers Definitive Demonstration of Myco tuberculosis ( smear/ culture) Histo /Cytological criteria

55. EPT: DIAGNOSIS Site Empirical/ Suggestive Possible Definitive 1 Lymph Nodes Clinical FNAC (Granuloma) AFB on FNAC 2. Pl. Effusion Clinico -radiological Exudative A.D.A. Pl. biopsy AFB positivity P.C.R. 3. Pericarditis As above As above As above 4. Peritoneal As above As above As above 5. Intestinal Clinical Radiological Biopsy Granuloma AFB positivity 6. Genitourinary Endoscopy As above Biopsy Granuloma AFB positivity 7. Bones & Joints Clinical Radiology FNAC Biopsy As above 8. Meningeal As above CSF (Biochem.) CSF – PCR AFB

56. Comparison of Various Diagnostic Tests for Diagnosis of TB Microscopy LED Microscopy GeneXpert MTB/RIF LAMP Solid Culture Liquid Culture Threshold (CFU/ml) 10,000 - 131 (106-176) - ~100 10-50 Turnaround time 1-2 days 1day 90 min - 4-8 week Days - 2 week Sensitivity 50-60 % 10% >than ZN staining ~90 % 88 % Reference Reference Specificity 98% 94 % Reference Reference Technical expertise Required Required Minimal Required Required Required Biosafety Better than Microscopy Other Prone to contamination Boehme CC et al. Semin Respir Crit Care Med 2013;34:17 – 31. Lawn SD et al. Lancet Infect Dis 2013; 13: 349–61.

57. Absence of e vidence is not the e vidence of a bsence Carl Sagan

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