Diagnostic Techniques In Tuberculosis

Diagnostic Techniques In Tuberculosis

Q. 1

 Tuberculin positive means?

 A Immunodeficient patient
 B Resistance to tuberculin protein
 C Patient is infected with mycobacterium
 D Patient is suffering from disease
Q. 1

 Tuberculin positive means?

 A Immunodeficient patient
 B Resistance to tuberculin protein
 C Patient is infected with mycobacterium
 D Patient is suffering from disease
Ans. C

Explanation:

 Patient is infected with mycobacterium REF: Park 20′ edition page 164

A positive test (reaction of 10 mm or more to 1 TU PPD) indicates that the person is infected with M. tuberculosis; it does not prove that the person is suffering from the disease


Q. 2 Tuberculin positivity means:
 A Immunodeficiency
 B Resistance to tubercular protein
 C Infection with mycobacterium
 D Patient suffering from disease 
Q. 2 Tuberculin positivity means:
 A Immunodeficiency
 B Resistance to tubercular protein
 C Infection with mycobacterium
 D Patient suffering from disease 
Ans. C

Explanation:

Infection with mycobacterium


Q. 3

50 year old, Rishi has a diagnosis of pulmonary tuberculosis. How many infectious nuclei per cough are likely to be seen in sputum examination?

 A

1000

 B

2000

 C

3000

 D

4000

Q. 3

50 year old, Rishi has a diagnosis of pulmonary tuberculosis. How many infectious nuclei per cough are likely to be seen in sputum examination?

 A

1000

 B

2000

 C

3000

 D

4000

Ans. C

Explanation:

Transmission of pulmonary TB to others is by droplet nuclei, which are aerosolized usually by coughing. The tiny droplets dry rapidly; the smallest (<5–10 m in diameter) may remain suspended in the air for several hours and may reach the terminal air passages when inhaled. There may be as many as 3000 infectious nuclei per cough.


Reference:
Harrisons Principles of Internal Medicine, 18th Edition, Page 1342


Q. 4

Mycobacterium tuberculosis is diffentiated from other atypical mycobacteria by –

 A

Niacin test

 B

AFB staining

 C

PAS staining

 D

None

Q. 4

Mycobacterium tuberculosis is diffentiated from other atypical mycobacteria by –

 A

Niacin test

 B

AFB staining

 C

PAS staining

 D

None

Ans. A

Explanation:

Ans. is ‘a’ i.e., Niacin test 

.       Niacin test is useful in identifying human strains (M. tuberculosis) as no other mycobacteria is positive except for M.

simiae and a few strains of M. cheloneii.


Q. 5

Mycobacterium tuberculosis can be differentiated from other mycobacteria by – 

 A

Production of Niacin 

 B

Aryl sulphatase test

 C

Coagulase test

 D

a and b

Q. 5

Mycobacterium tuberculosis can be differentiated from other mycobacteria by – 

 A

Production of Niacin 

 B

Aryl sulphatase test

 C

Coagulase test

 D

a and b

Ans. D

Explanation:

Ans. is ‘a’ i.e., Production of Niacin; ‘b’ i.e., Aryl sulphatase test 


Q. 6

The most appropriate test to assess the prevalence of tuberculosis infection in a community is – 

 A

Mass miniature radiotherapy

 B

Sputum examination

 C

Tuberculin test

 D

Clinical examination

Q. 6

The most appropriate test to assess the prevalence of tuberculosis infection in a community is – 

 A

Mass miniature radiotherapy

 B

Sputum examination

 C

Tuberculin test

 D

Clinical examination

Ans. C

Explanation:

Ans. is ‘c’ i.e., Tuberculin test 

Epidemiological indices of tuberculosis

  • Indices or parameters are needed to measure the tuberculosis problem in a community as well as for planning and evaluation of control measures.

o The following epidemiological-indices are used in tuberculosis problem measurement and programme strategy :‑

1. Prevalence of infection

                       It is the percentage of individuals who show a positive reaction to the standard tuberculin test.

2. Incidence of infection (Annual infection rate) =.1 it is the percentage of population under study who will be newly infected by M.tuberculosis among the non-infected of the preceding survey during the course of one year.

          It reflects the annual risk of being infected (or reinfected) in a given community, i.e. it expresses the attacking force of tuberculosis in a community.

          It is also known as tuberculin conversion index.

          This parameter is considered one of the best indicators for evaluating the tuberculosis problem and its trend.

3. Prevalence of disease or case rate

                       It is the percentage of individuals whose sputum is positive for tubercle bacilli on microscopic examination.

It is the best available practical index to estimate the number of infectious cases or case load in a community.


Q. 7

Prevalance of tuberculosis infection is determined by-

 A

Sputum examination

 B

Mantoux

 C

Clinical examination

 D

MMR

Q. 7

Prevalance of tuberculosis infection is determined by-

 A

Sputum examination

 B

Mantoux

 C

Clinical examination

 D

MMR

Ans. B

Explanation:

Ans. is ‘b’ i.e., Montoux 

o You should keep it in mind that not every person who is infected by M. tuberculosis will develop the disease.

o So, the prevalence (or incidence) of infected persons will be different (obviously more) from the prevalence (or incidence) of diseased persons (cases).


Q. 8

False-negative tuberculin test is seen in all except:

 A

After 4-6 weeks of measles attack

 B

Immunodeficiency state

 C

Miliary tuberculosis

 D

Atypical mycobacterial infection

Q. 8

False-negative tuberculin test is seen in all except:

 A

After 4-6 weeks of measles attack

 B

Immunodeficiency state

 C

Miliary tuberculosis

 D

Atypical mycobacterial infection

Ans. D

Explanation:

Answer is D (Atypical mycobacterial infection):

Infection with atypical mycobacteria or other related mycobacteria are associated with false positive reactions and not false negative tests.

False negative tuberculin tests (Anergy) may occur in.situations such as :

  • Miliary tuberculosisQ
  • Convalescence from some viral infections like Measles e
  • Lymphoreticular malignancy
  • Sarcoidosis Q
  • Severe malnutrition Q
  • Immunosuppressive therapy
  • Defective cell mediated immunityQ

Q. 9

Investigations in a clinically suspected case of tuberculosis –

 A

Mantoux (in children)

 

 B

Sputum AFB

 C

PCR

 D

All of the above

Q. 9

Investigations in a clinically suspected case of tuberculosis –

 A

Mantoux (in children)

 

 B

Sputum AFB

 C

PCR

 D

All of the above

Ans. D

Explanation:

Answer is D (All of the above):

Montoux testing, sputum for AFB, PCR and BACTEC (culture method) may all be used fo establish the diagnosis of Tuberculosis.


Q. 10

Confirmatory test for tuberculosis is:

September 2006

 A

Gram’s staining

 B

AFB

 C

Guinea-pig inoculation

 D

Tuberculin testing

Q. 10

Confirmatory test for tuberculosis is:

September 2006

 A

Gram’s staining

 B

AFB

 C

Guinea-pig inoculation

 D

Tuberculin testing

Ans. B

Explanation:

Ans. B: AFB

The diagnosis of tuberculosis requires detection of acid-fast bacilli in sputum via the Ziehl-Neelsen method Mycobacteria retains the primary stain even after exposure to decolorising acid-alcohol, hence the term ‘acid-fast’. A counter-stain is employed to highlight the stained organisms for easier recognition. There are several methods of determining the acid-fast nature of mycobacteria. In the carbolfuchsin (Ziehl-Neelsen) procedure, acid-fast organisms appear red against a blue background, while in the fluorochrome procedures (auramine-O, auramine-rhodamine), the acid-fast organisms appear as fluorescent rods, yellow to orange (the colour may vary with the filter system used) against a paler yellow or orange background.

Tuberculin testing may be used as an aid in diagnosing active infection in infants and young children,to measure prevalence of infection in an area, to select susceptible or as an indication of successful vaccination.


Q. 11

Fastest method for diagnosis of TB –

 A

Gene expert

 B

LJ medium

 C

TB MGIT

 D

BAC, IEC

Q. 11

Fastest method for diagnosis of TB –

 A

Gene expert

 B

LJ medium

 C

TB MGIT

 D

BAC, IEC

Ans. A

Explanation:

Ans. is ‘a’ i.e., Gene expert

GeneXpert MTB/RIF

  • The Xpert MTB/RIF detects DNA sequences specific for Mycobacterium tuberculosis and rifampicin resistance by polymerase chain reaction.
  • It is based on the Cepheid GeneXpert system, a platform for rapid and simple-to-use nucleic acid amplification tests (NAAT).
  • The Xpert MTB/RIF purifies and concentrates Mycobacterium tuberculosis bacilli from sputum samples, isolates genomic material form the captured bacteria by sonication and subsequently amplifies the genomic DNA by PCR.
  • The process identifies all the clinically relevant rifampicin resistance inducing mutations in the RNA polymerase beta (rpoB) gene in the mycobacterium tuberculosis genome in a real time format using fluorescent probes called molecular beacons.
  • Results are obtained from unprocessed sputum samples in 90 minutes, with minimal biohazard and very little technical training required to operate.

Q. 12

Which type of pulmonary TB is most likely to give sputum positive ‑

 A

Fibronodular

 B

Pleural effusion

 C

Cavitary

 D

None

Q. 12

Which type of pulmonary TB is most likely to give sputum positive ‑

 A

Fibronodular

 B

Pleural effusion

 C

Cavitary

 D

None

Ans. C

Explanation:

Ans. is ‘c’ i.e., Cavitary

Sputum smears are usually positive in patients with laryngeal TB, endobronchial TB and cavitary pulmonary TB” — Kelley ‘s

“Patients with cavitary pulmonary TB have high bacterial load in their sputum”       — Internet


Q. 13

Fastest method for diagnosis of TB ‑

 A

Gene expert

 B

LI medium

 C

TB MGIT

 D

BAC IEC

Q. 13

Fastest method for diagnosis of TB ‑

 A

Gene expert

 B

LI medium

 C

TB MGIT

 D

BAC IEC

Ans. A

Explanation:

Ans. is ‘a’ i.e., Gene expert


Q. 14

Radiomimetric BACTEC detect growth of M tuberculosis in how much time ‑

 A

1 week

 B

2-3 week

 C

4-8 week

 D

> 10 weeks

Q. 14

Radiomimetric BACTEC detect growth of M tuberculosis in how much time ‑

 A

1 week

 B

2-3 week

 C

4-8 week

 D

> 10 weeks

Ans. B

Explanation:

Ans. is `b’ i.e., 2-3 weeks


Q. 15

All selective media are correctly matched except ‑

 A

V cholerae – TCBS medium

 B

Pseudomonas – Cetrimide agar

 C

M tuberculosis – LJ medium

 D

Campylobacter – BCYE medium

Q. 15

All selective media are correctly matched except ‑

 A

V cholerae – TCBS medium

 B

Pseudomonas – Cetrimide agar

 C

M tuberculosis – LJ medium

 D

Campylobacter – BCYE medium

Ans. D

Explanation:

Ans. is ‘d’ i.e., Campylobacter – BCYE medium


Q. 16

Role of Malachite green in LJ medium ‑

 A

Increase growth of M. tuberculosis

 B

Inhibits growth of other bacteria

 C

Nutritive value

 D

As an indicator

Q. 16

Role of Malachite green in LJ medium ‑

 A

Increase growth of M. tuberculosis

 B

Inhibits growth of other bacteria

 C

Nutritive value

 D

As an indicator

Ans. B

Explanation:

Ans. is ‘b’ i.e., Inhibits growth of other bacteria

Lowenstein-Jensen Medium (LJ medium)

LJ medium consists of mineral salts, asparagine, glycerol, malachite green and hen’s egg.

The malachite green prevents the growth of other microorganism on medium.

It is used as a primary isolation medium for mycobacteria.


Q. 17

Gene expert used for getting diagnosis of TB in ‑

 A

1-2 hrs

 B

5 hrs.

 C

10 hrs.

 D

20 hrs.

Q. 17

Gene expert used for getting diagnosis of TB in ‑

 A

1-2 hrs

 B

5 hrs.

 C

10 hrs.

 D

20 hrs.

Ans. A

Explanation:

Ans. is ‘a’ i.e., 1-2 hrs.

Results are obtained from unprocessed sputum samples in 90 minutes, with minimal biohazard and very little technical traning required to operate.


Q. 18

LJ media is used for ‑

 A

Bacillus antracis

 B

M. tuberculosis

 C

Leptospira

 D

Legionella

Q. 18

LJ media is used for ‑

 A

Bacillus antracis

 B

M. tuberculosis

 C

Leptospira

 D

Legionella

Ans. B

Explanation:

Ans. is ‘b’ i.e., M tuberculosis

The solid medium most widely employed for routine culture of tubercular is Lowenstein – Jensen Medium (L.J. medium).


Q. 19

Rapid test used by WHO for tuberculosis ‑

 A

Quanteferon gold

 B

ELISPOT

 C

Xpert MTB

 D

Sputum AFB

Q. 19

Rapid test used by WHO for tuberculosis ‑

 A

Quanteferon gold

 B

ELISPOT

 C

Xpert MTB

 D

Sputum AFB

Ans. D

Explanation:

Ans. is ‘d’ i.e., Sputum AFB

Sputum smear microscopy is the quickest and easiest procedure. But it lacks both sensitivity and specificity.

  • Smears are stained by ziehl-Neelsen acid-fast stain.
  • Sputum smear examination (by AFB stain) is the method of choice for case finding.

Note : Genexpert MTB/RIF is also a fast test (results within 90 minutes), but it is not routinely recommended by WHO.


Q. 20

As per RNTCP guidelines first do in TB suspect case ‑

 A

Chest X-ray

 B

Sputum culture

 C

Sputum microscopy

 D

Start short-course chemotherapy

Q. 20

As per RNTCP guidelines first do in TB suspect case ‑

 A

Chest X-ray

 B

Sputum culture

 C

Sputum microscopy

 D

Start short-course chemotherapy

Ans. C

Explanation:

Ans. is ‘c’ i.e., Sputum microscopy

Treatment stratgics in RNTCP

  • Under the RNTCP active case finding is not prusued.
  • Case finding is passive.
  • Patients presenting thremselves with symptoms suspicious of tuberculosis are screened through 2 sputum smear examination.
  • Sputum microscopic examination is done in designated RNTCP microscopy centres.
  • It is essential to examine 2 sputum specimens of each patient before a conclusive diagnosis can be made. 
  • If only 1 sputum smear is positive, chest x-ray helps in diagnosis.
  • Once the diagnosis is confirmed, treatment is started according to DOTS (Directly observed therapy short term).
  • Patient are expected to collect drugs once a month (not daily) on fixed dates from the nearest treatment centre.

Q. 21

Most rapid diagnosis of pulmonary TB can be done by ‑

 A

Sputum culture

 B

Sputum microscopy

 C

Radiometric BACTEC method

 D

Genexpert

Q. 21

Most rapid diagnosis of pulmonary TB can be done by ‑

 A

Sputum culture

 B

Sputum microscopy

 C

Radiometric BACTEC method

 D

Genexpert

Ans. B

Explanation:

Ans. is ‘b’ i.e., Sputum microscopy

  • Sputum smear microscopy is the quickest and easiest procedure. But it lacks both sensitivity and specificity.
  • Sputum culture is sensitive and most specific. But it takes 2-8 weeks for culture on routine L.J. media (solid medium).
  • M tuberculosis produces visible colonies on solid media (L.J. media) in 4-8 weeks.
  • Studies have shown that the rate of Isolation of positive cultures was significantly faster with the Bactec method  with 87% of the positives being obtained at 7 days and  96% by 14 days.
  • Gene XPert should be used as the initial diagnostic test in individuals suspected of having MDR-TB or HIV-associated TB (strong recommendation),” and “Xpert may be used as a follow-on test to microscopy where MDR and/or HIV are of lesser concern, especially in smear-negative specimens (conditional recommendation).
    • The GeneXpert MTB/RIF assay is a novel integrated diagnostic device for the diagnosis of tuberculosis and rapid detection of RIF resistance in clinical specimens.

Q. 22

The medium showed in the diagram is used to identify 

 A

Bacillus antracis

 B

M. tuberculosis

 C

Leptospira

 D

Legionella

Q. 22

The medium showed in the diagram is used to identify 

 A

Bacillus antracis

 B

M. tuberculosis

 C

Leptospira

 D

Legionella

Ans. B

Explanation:

The solid medium most widely employed for routine culture of tubercular is Lowenstein – Jensen Medium (L.J. medium).



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