cursuri tb

8/7/2019 CURSURI TB

1/52

Diagnosis of Pulmonary

Tuberculosis

Presenter: 4A Ri

Sep. 29,2008

8/7/2019 CURSURI TB

2/52

Why diagnosis important?

Diagnosis of tuberculosis in most cases clinical diagnosis based upon the clinical presentation

(hx & PE)

In 15-20% of pt with suspected TB lab confirmation never obtained

Early diagnosis and initiation of effectivetherapy

reducing morbidity and mortality from TB

minimize the spread of infection

8/7/2019 CURSURI TB

3/52

Outline

Screening for prior infection

Tuberculin skin test

Diagnosis of pulmonary TB Medical history

Physical examination

Chest radiograph

Bacteriologic exam

8/7/2019 CURSURI TB

4/52

Screening for prior infectionTuberculin skin test

8/7/2019 CURSURI TB

5/52


Whom to screen High prevalence and high risk population

(HIV)

How to screen Mantoux tuberculin test (ie, purified protein

derivative or PPD, tuberculin skin test)

How to interpret Determine maximum diameter of indurationby palpation

8/7/2019 CURSURI TB

6/52

Mantoux Tuberculin Test

Preferred method of testing for TBinfection in adults and children

Tuberculin skin testing useful for Examining person who is not ill but may be

infected

Determining how many people in group are

infected

Examining person who has symptoms of TB

8/7/2019 CURSURI TB

7/52

Mantoux test

Inject intradermally0.1 ml of 5TU PPDtuberculin

Produce wheal 6 mmto 10 mm in diameter

Represent DTH

(delayed typehypersensitivity)

8/7/2019 CURSURI TB

8/52

Reading ofMantoux test

Read reaction 48-72hours after injection

Measure onlyinduration

Record reaction inmm

8/7/2019 CURSURI TB

9/52

Classifying the tuberculin reaction

>5 mm is classified as positive in

HIV-positive persons

Recent contacts of TB case Persons with fibroticchanges on CXR

consistent with old healed TB

Patients with organ transplants and other

immunosuppressed patients

8/7/2019 CURSURI TB

10/52


>10 mm is classified as positive in Recent arrivals from high-prevalence

countries

Injection drug users Residents and employees of high-risk settings

Mycobacteriology laboratory personnel

Persons with clinicalconditions that placethem at high risk

Children

8/7/2019 CURSURI TB

11/52


>15 mm is classified as positive in

Persons with no known risk factors for TB

8/7/2019 CURSURI TB

12/52

Factors may affect TST

False negative Faulty application

Anergy

Acute TB (2-10 wks to convert) Very youngage (< 6 months old)

Live-virus vaccination

Overwhelming TB disease

False positive BCG vaccination (usually

8/7/2019 CURSURI TB

13/52

Boosting

Some people with LTBI may havenegative skin test reaction when tested

years after infection Initial skin test may stimulate (boost)ability to react to tuberculin

Positive reactions to subsequent tests maybe misinterpreted as a new infection

8/7/2019 CURSURI TB

14/52

Two-Step Testing

Use two-step testing for initial skin testingof adults who will be retested within 1-3weeks

If first test (+), consider the person infected

If first test (-), give second test 1-3 weeks later

If second test (+), consider person infected

If second test (-), consider person uninfected

8/7/2019 CURSURI TB

15/52


5020 80% TST

,TST

8/7/2019 CURSURI TB

16/52

Diagnosis of Pulmonary TB

8/7/2019 CURSURI TB

17/52

Diagnosis of disease

Medical history

Physical examination Chest radiograph

Bacteriologic exam

AFS Culture

8/7/2019 CURSURI TB

18/52

Medical History

8/7/2019 CURSURI TB

19/52

Medical History

Symptoms of disease

History of TB exposure, infection, or

disease Past TB treatment

Demographic risk factors for TB

Medicalconditions that increase risk forTB disease

8/7/2019 CURSURI TB

20/52

Medical History

High prevalence population

More likely to be exposed to and infected withbacillus

Immigrant from high prevalence area

Resident or worker in jail

Long term care facility

Close contact to pt with active TB

8/7/2019 CURSURI TB

21/52

Medical History

High risk population More likely to progress from infection to active TB

HIV (+) or other immunodeficiency

CRF DM

IVDA

Alcoholics

Malnourished

Malignancy

Gastrectomy

8/7/2019 CURSURI TB

22/52

Ph

ysical Examination

8/7/2019 CURSURI TB

23/52

Physical Examination

Productive, prolonged cough duration of ~3 weeks

Chest pain

Hemoptysis Fever/Chills

Night sweats

Appetite loss

Weight loss

Easily fatigued

8/7/2019 CURSURI TB

24/52

Chest radiograp

hy

8/7/2019 CURSURI TB

25/52

Chest radiography

Classical radiograph appearance Infiltration

Cavitation

Fibrosis with traction Enlargement of hilar and mediastinallymph node

In reactivaiton TB

Classically fibrocavitary apical disease

Primary TB Middle or lower lobe consolidation

8/7/2019 CURSURI TB

26/52

Chest radiography

Abnormalities oftenseen in apical orposterior segments of

upper lobe orsuperior segments oflower lobe

May have unusualappearance in HIV-positive persons

Cannot confirmdiagnosis of TB!!

cavity in patients RULclassic" for adult-type, reactivation tuberculosis

8/7/2019 CURSURI TB

27/52

Classic adult TB CXR

PA view

diffuse parenchymaldisease with multiplecavities and bullaformation on the left

Sputum smear waspositive for AFB

8/7/2019 CURSURI TB

28/52

Chest radiography

No chest X-ray pattern is absolutelytypical of TB

10-15% of culture-positive TB patients notdiagnosed by X-ray

40% of patients diagnosed as having TBon the basis of x-ray alone do not haveactive TB

8/7/2019 CURSURI TB

29/52

0

20

40

60

80

100

Diagnosed by X-

ray alone

Actual cases

X

-ray-based evaluation causesover-diagnosis of TB

NTI, Ind J Tuberc, 1974

Over-

diagnosis

8/7/2019 CURSURI TB

30/52

Bacteriologic Exam

8/7/2019 CURSURI TB

31/52

Specimen Collection

Obtain 3 sputum specimens for smearexamination and culture

Persons unable to cough up sputum induce sputum bronchoscopy

gastricaspiration

Follow infection control precautionsduring specimen collection

8/7/2019 CURSURI TB

32/52

Three Specimens

Three specimens optimal

Spot specimen on first visit; sputum containergiven to patient

Early morningcollection by patient on nextday

Spot specimen during second visit

8/7/2019 CURSURI TB

33/52

Three sputum smears are optimal

81%

93%

100%

0%

50%

100%

First Second ThirdCumulativePositivity

8/7/2019 CURSURI TB

34/52

Number of sputum samples required

overall diagnostic yield for sputumexamination related to

the quantity of sputum (at least 5 mL)

the quality of sputum

multiple samples obtained at different timesto the laboratory for processing

3 samples obtained at least eight hours apart withat least one sample obtained in the early morning

8/7/2019 CURSURI TB

35/52

Number of sputum samples required

several studies have suggested that only twosamples may be sufficient to capture themajority of cases:

R

etrospective study Nelson, SM, Deike,MA, Cartwright, CP. Value of examining multiple sputumspecimens in the diagnosis of pulmonary tuberculosis. J ClinMicrobiol 1998; 36:467.

overall, 92 percent of cases would have beendetected with two specimens

Craft, DW, Jones, MC, Blanchet, CN, et al. Value of examining three acid-fact bacillus

sputum smears for the removal of patients suspected of having tuberculosis from the"airborn precautions"category. J Clin Microbiol 2000; 38:4285.

a third sputum smear was of no additionalvalue

8/7/2019 CURSURI TB

36/52

Smear Examination

Strongly consider TB in patients withsmears containingacid-fast bacilli (AFB)

Results should be available within 24hours of specimen collection

Presumptive diagnosis of TB

Not specific for M. tuberculosis

8/7/2019 CURSURI TB

37/52

AFB Smear

Sensitivity: 40-70%

Specificity: 90%

8/7/2019 CURSURI TB

38/52

8/7/2019 CURSURI TB

39/52

Reporting on AFBMicroscopy

Number ofbacilli seen Result reported

None per 100 oil immersion fields Negative

1-9 per 100 oil immersion fields Scanty, reportexact number

10-99 per 100 oil imm

ersion fields 1+

1-10 per oil immersion field 2+

> 10 per oil immersion field 3+

8/7/2019 CURSURI TB

40/52

Proportion of patients with pulmonary

TB who have positive AFB smears

0

10

20

30

40

50

60

70 HIVNegative

Early HIV

Late HIV

AFB positivity in

TB patients

8/7/2019 CURSURI TB

41/52

Open tuberculosis

A tuberculous ulceration or other form of

tuberculosis in wh

ich

tubercle bacilli arepresent in the excretions or secretions.

Pulmonary tuberculosis, especially withcavitation.

8/7/2019 CURSURI TB

42/52

Cultures

Colonies of

M. tuberculosisgrowing on media

Gold standard for TB diagnosisUse to confirm diagnosis of TBCulture all specimens, even if smear negativeResults in 4 to 14 days when liquid mediumsystems used

8/7/2019 CURSURI TB

43/52

Cultures

Sensitivity: 80-85%

Specificity: 98%

Times needed: Solid medium

4-8 wks

Liquid medium

2 wks

8/7/2019 CURSURI TB

44/52

AFB smear vs. Cultures

AFB smear

ml5000-10000

Rapid diagnosis

Cultures

ml10-100

More sensitive

Allows drug susceptivity test

8/7/2019 CURSURI TB

45/52

98%

70%

0

20

40

60

80

100

AFB Microscopy X-ray

Microscopy is more objective

and reliable than X-ray

Inter-observer

agreement

8/7/2019 CURSURI TB

46/52

50%

98%

0

20

40

60

80

100

AFB Microscopy X-ray

M

icroscopy is a more specific test th

anX-ray for TB diagnosis

Specificity

8/7/2019 CURSURI TB

47/52

Diagnosis of Pulmonary TBCough 3 weeks

AFB X 3

Broad-spectrum antibiotic 10-14 days

If symptoms persist, repeat AFB smears, X-ray

If consistent with TB

Anti-TB Treatment

If 1 positive,

X-ray andevaluation

If 2/3 positive:Anti-TB Rx

Ifnegative:

8/7/2019 CURSURI TB

48/52

Diagnosis of pulmonary TB

8/7/2019 CURSURI TB

49/52

Recommended DiagnosticApproach

8/7/2019 CURSURI TB

50/52

Take HomeMessage

Non-specific symptoms

Often over diagnosis

AFB smear

Rapid diagnosis, presumptive diagnosis

Culture

Gold standard, more sensitive

TB

8/7/2019 CURSURI TB

51/52

Source

UpToDate, Diagnosis of pulmonarytuberculosis, 2008, John Bernardo,MD

,

,Taiwan Guidelines on TB Diagnosis &Treatment, Edition 3,

8/7/2019 CURSURI TB

52/52

Th

anks for your attention!

cursuri tb

Documents