OSPE TB

Question 1

Case

Answer 1

-low-grade fever
-evening rise in temp
-productive cough for 2 months
-blood-tinged sputum
-loss of appetite
-weight loss
chest X-ray: nodular infiltrate in apical area of R upper lobe
+ve for acid fast bacilli
grow colonies on LJ media

Question 2

Sample collection

Answer 2

1.Sputum
-morning b4 meals,for 3 days

2.laryngeal aspirates or bronchial washings

3. children: gastric lavage

Question 3

liquefaction, decontamination and concentration

Answer 3

Petroff’s method:
-The sputum was transferred to a sterile test tube and an equal amount of sterile 4% NaOH
- incubated at 370c for 30 minutes with vigorous shaking every 5 minutes.
-centrifuged at 3,000 rpm for 30 minutes and the supernatant poured off.
- deposit is neutralized by N/10HCl using a drop of phenol red as indicator.

• NALC (N acetylcysteine) combined with 2% NaOH: Better method than Petroff’s. N acetylcysteine is used for liquefaction of sputum.
  NaOH kills the contaminating bacteria.
  The sample is then neutralised with buffer and concentrated by centrifugation.

Question 4

Microscopy of sputum

Answer 4

Acid fast staining:Acid fast bacilli
auramine-rhodamine stain: (fluorescent apple-green)

Question 5

Mantoux Test

Answer 5

-measure zone of induration
≥5 mm in HIV + or anyone with recent TB exposure;

≥ 10 mm in high-risk population: IV drug abusers, people living in poverty, or immigrants from high TB area

≥ 15 mm in low-risk population

Positive skin test indicates exposure but not necessarily active disease.Vaccine might also give positive results

Question 6

Interferon-Gamma Release Assays

Answer 6

do not help differentiate latent tuberculosis infection (LTBI) from tuberculosis disease.

Question 7

Lowenstein- Jensen medium

Answer 7

• Slow-growing (3-6 weeks) colonies
  -dyes inhibit the unwanted normal flora present in sputum samples.
• Rough, Tough, Buff colonies.

Question 8

BACTEC liquid medium

Answer 8

rows more rapidly, can be detected by the production of radioactive carbon dioxide in about 2 weeks.
* Niacin and catalase positive

Question 9

Lateral Flow Urine Lipoarabinomannan Assay LF-LAM

Answer 9

-detects lipoarabinomannan, a component of the mycobacterial cell wall, within one hour
-easier to perform and without the risk of laboratory TB transmission.

Question 10

Chest radiography

Answer 10

-used as the primary imaging modality
-abnormalities seen in the apical and posterior segments of the upper lobe or in the superior segments of the lower lobe.

Question 11

latest

Answer 11

Xpert Ultra