Recent and complete laboratory investigations for pulmonary tuberculosis

1. LAB DIAGNOSIS OF
PULMONARY TUBERCULOSIS
- Yasminbanu S
4th Year MBBS

2. INTRODUCTION
Tuberculosis (TB) is a potentially fatal contagious disease that
can affect almost any part of the body but is mainly an
infection of the lungs.
Tubercle – Round Nodule / Swelling
Osis – Condition

3. CAUSATIVE ORGANISM
Mycobacterium Tuberculosis – Human

4. SYMPTOMS

5. DIAGNOSIS OF ACTIVE TB
Specimen Collection
Digestion, decontamination and concentration of specimen
Direct microscopy
Culture methods
Drug Sensitivity Test
Biochemical identification
Molecular methods
Serology (Not useful)

6. SPECIMEN COLLECTION
ADULT
• Pulmonary TB – Rinse mouth with water – Deep Coughing – 2 sputum specimens
– spot and early morning – in wide mouth sterile container
• Ideal sputum sample should have
• Pus Cells > 25 and Epithelial Cells < 25
• If previous is not available - Laryngeal Aspirate or Bronchial washings – Collected
CHILDREN
• Gastric Aspirate

7. DIGESTION, DECONTAMINATION,
CONCENTRATION OF SPECIMEN
2 Methods
•Petroff’s method (Commonly Used)
•NALC + 2% NaOH

8. DIRECT MICROSCOPY
• Ziehl – Neelsen Technique – Long slender, beaded, uniformly stained acid fast
bacilli
• Kinyoun’s cold acid fast staining
• Auramine Phenol technique
• Acid Alcohol (3% HCl + 95% Ethanol) used
to differentiate between MTB and saprophytic mycobacterium

9. AFB GRADING OF SPUTUM

10. CULTURE METHODS
Solid medium – LJ
medium (takes 6 to 8
weeks) – shows rough,
tough and buff colonies
Liquid medium – middle
brook 7H9 medium
Automated systems –
BACTEC MGIT, BacT-
ALERT(takes 2 to 3 weeks)

11. DRUG SENSITIVITY TESTS
• Both phenotypic [preferred mostly] and genotypic methods are available
• PROPORTION METHOD: gold standard method
• Proportion of drug No. of colonies growing on drug containing medium
resistant bacilli No. of colonies growing on drug free medium
• Other methods include
• ABSOLUTE CONCENTRATION METHOD
• RESISTANCE RATIO METHOD
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12. BIOCHEMICAL IDENTIFICATION
•Niacin test +ve
•Nitrate reduction test +ve
•Pyranzinamidase test +ve
•Resistant to TCH
The
following
tests
differentiate
MTB from
M.bovis

13. BIOCHEMICAL IDENTIFICATION
CONT..
•Aryl sulfatase test
•Catalase-peroxidase
test
•Tween 80 hydrolysis test
THESE TEST
DIFFERENTIATE
MTB FROM
ATB

14. MOLECULAR METHODS
• PCR & LCR done
• GeneXpert/CB-NAAT (Cartridge
based nucleic acid amplification
test)
• Highly sensitive TB test, high
accuracy compared to smear
microscopy
• zero cost to patient, detect
resistance to rifampicin drug.
• Molecular typing:
• IS6110 RFLP typing
• Spoligotyping

15. DIAGNOSIS OF LATENT TB
• Tuberculin test
• Antigen – PPD
• Dosage – .1 ml (5TU)
• Site – ID in flexor aspect of forearm
• Reading – looked for induration after 48 to 72 hrs.
• >= 10 mm positive
• 6 – 9 mm equivocal
• < 5 mm negative
• False positive: BCG & ATB
• False negative: Early and miliary TB

16. DIAGNOSIS OF LATENT TB CONT..
INTERFERON GAMMA RELEASE
ASSAY(IGRA)/QuantiFERON
ASSAY:
• This test uses highly specific
M.tuberculosis antigen –CFP10
&ESAT6
Advantage : No False Positive
Conditions

17. UPCOMING METHODS IN TB DIAGNOSIS
Chip based
real-time PCR
(TrueNat)
TB-LAMP (Loop-
Mediated
Isothermal
Amplification)
Next
Generation
Gene Xpert
(Xpert Ultra)
Breath
biomarkers
LAM
(Lipoarabinom
annan)
Antigen
Detection
IRISA TB
(InterGam
Rapid Immuno
Suspension
Assay)

18. MANAGEMENT
Intensive phase + Continuation Phase
2 HRZE + 4 HRE

19. DRUG RESISTANCE IN TB
MDR-TB - Resistant to ISONIAZID + RIFAMPICIN
XDR-TB - MDR + fluoroquinolone +
injectable 2nd line drugs
PDR-TB – Resistant to ALL DRUGS

20. THANK YOU 