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Diagnosis Of Pulmonary Tb
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Diagnosis Of Pulmonary Tb

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Diagnosis Of Pulmonary Tb Diagnosis Of Pulmonary Tb Presentation Transcript

  • Diagnosis of Pulmonary Tuberculosis Presenter: 4A Ri 范綱志 Sep. 29,2008
  • Why diagnosis important?
    • Diagnosis of tuberculosis in most cases
      • clinical diagnosis based upon the clinical presentation (hx & PE)
    • In 15-20% of p’t with suspected TB
      • lab confirmation never obtained
    • Early diagnosis and initiation of effective therapy
      • reducing morbidity and mortality from TB
      • minimize the spread of infection
  • Outline
    • Screening for prior infection
      • Tuberculin skin test
    • Diagnosis of pulmonary TB
      • Medical history
      • Physical examination
      • Chest radiograph
      • Bacteriologic exam
  • Screening for prior infection Tuberculin skin test 篩出感染者
  • Screening for prior infection
    • 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 induration by palpation
  • Mantoux Tuberculin Test
    • Preferred method of testing for TB infection 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
  • Mantoux test
    • Inject intradermally 0.1 ml of 5TU PPD tuberculin
    • Produce wheal 6 mm to 10 mm in diameter
    • Represent DTH (delayed type hypersensitivity)
  • Reading of Mantoux test
    • Read reaction 48-72 hours after injection
    • Measure only induration
    • Record reaction in mm
  • Classifying the tuberculin reaction
    • > 5 mm is classified as positive in
      • HIV-positive persons
      • Recent contacts of TB case
      • Persons with fibrotic changes on CXR consistent with old healed TB
      • Patients with organ transplants and other immunosuppressed patients
  • Classifying the tuberculin reaction
    • >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 clinical conditions that place them at high risk
      • Children <4 years, or children and adolescents exposed to adults in high-risk categories
  • Classifying the tuberculin reaction
    • > 15 mm is classified as positive in
      • Persons with no known risk factors for TB
  • Factors may affect TST
    • False negative
      • Faulty application
      • Anergy
      • Acute TB (2-10 wks to convert)
      • Very young age (< 6 months old)
      • Live-virus vaccination
      • Overwhelming TB disease
    • False positive
      • BCG vaccination (usually <10mm by adulthood)
      • Nontuberculous mycobacteria infection
  • Boosting
    • Some people with LTBI may have negative skin test reaction when tested years after infection
    • Initial skin test may stimulate (boost) ability to react to tuberculin
    • Positive reactions to subsequent tests may be misinterpreted as a new infection
  • Two-Step Testing
    • Use two-step testing for initial skin testing of adults who will be retested within 1-3 weeks
      • 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
  • Screening for prior infection
    • 台灣早年結核病盛行率高
    • 50 年前 20 歲以上成人
      • 80% TST 為陽性
    • 年齡越大 ,TST 對結核病的診斷幫助越小
  • Diagnosis of Pulmonary TB
  • Diagnosis of disease
    • Medical history
    • Physical examination
    • Chest radiograph
    • Bacteriologic exam
      • AFS
      • Culture
  • Medical History
  • Medical History
    • Symptoms of disease
    • History of TB exposure, infection, or disease
    • Past TB treatment
    • Demographic risk factors for TB
    • Medical conditions that increase risk for TB disease
  • Medical History
    • High prevalence population
      • More likely to be exposed to and infected with bacillus
        • Immigrant from high prevalence area
        • Resident or worker in jail
        • Long term care facility
        • Close contact to p’t with active TB
  • 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
  • Physical Examination
  • Physical Examination
    • Productive, prolonged cough
      • duration of ~ 3 weeks‏
    • Chest pain
    • Hemoptysis
    • Fever/Chills
    • Night sweats
    • Appetite loss
    • Weight loss
    • Easily fatigued
  • Chest radiography
  • Chest radiography
    • Classical radiograph appearance
      • Infiltration
      • Cavitation
      • Fibrosis with traction
      • Enlargement of hilar and mediastinal lymph node
    • In reactivaiton TB
      • Classically fibrocavitary apical disease
    • Primary TB
      • Middle or lower lobe consolidation
  • Chest radiography
    • Abnormalities often seen in apical or posterior segments of upper lobe or superior segments of lower lobe
    • May have unusual appearance in HIV-positive persons
    • Cannot confirm diagnosis of TB!!
    cavity in patient‘s RUL classic&quot; for adult-type, reactivation tuberculosis
  • Classic adult TB CXR
    • PA view
      • diffuse parenchymal disease with multiple cavities and bulla formation on the left
      • Sputum smear was positive for AFB
  • Chest radiography
    • 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-based evaluation causes over-diagnosis of TB NTI, Ind J Tuberc, 1974 Over- diagnosis
  • Bacteriologic Exam
  • Specimen Collection
    • Obtain 3 sputum specimens for smear examination and culture
    • Persons unable to cough up sputum
      • induce sputum
      • bronchoscopy
      • gastric aspiration
    • Follow infection control precautions during specimen collection
  • Three Specimens
    • Three specimens optimal
      • Spot specimen on first visit; sputum container given to patient
      • Early morning collection by patient on next day
      • Spot specimen during second visit
  • Three sputum smears are optimal
  • Number of sputum samples required
    • overall diagnostic yield for sputum examination related to
      • the quantity of sputum (at least 5 mL)
      • the quality of sputum
      • multiple samples obtained at different times to the laboratory for processing
        • 3 samples obtained at least eight hours apart with at least one sample obtained in the early morning
  • Number of sputum samples required
    • several studies have suggested that only two samples may be sufficient to capture the majority of cases:
      • Retrospective study
        • Nelson, SM, Deike , MA, Cartwright, CP. Value of examining multiple sputum specimens in the diagnosis of pulmonary tuberculosis. J Clin Microbiol 1998; 36:467.
          • overall, 92 percent of cases would have been detected 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 &quot; airborn precautions&quot; category. J Clin Microbiol 2000; 38:4285.
          • a third sputum smear was of no additional value
  • Smear Examination
    • Strongly consider TB in patients with smears containing acid-fast bacilli (AFB)‏
    • Results should be available within 24 hours of specimen collection
    • Presumptive diagnosis of TB
    • Not specific for M. tuberculosis
  • AFB Smear
    • Sensitivity: 40-70%
    • Specificity: 90%
  • AFB smear AFB (shown in red) are tubercle bacilli
  • Reporting on AFB Microscopy Number of bacilli seen Result reported None per 100 oil immersion fields Negative 1-9 per 100 oil immersion fields Scanty, report exact number 10-99 per 100 oil immersion fields 1+ 1-10 per oil immersion field 2+ > 10 per oil immersion field 3+
  • Proportion of patients with pulmonary TB who have positive AFB smears AFB positivity in TB patients 0 10 20 30 40 50 60 70 HIV Negative Early HIV Late HIV
  • Open tuberculosis
    • A tuberculous ulceration or other form of tuberculosis in which tubercle bacilli are present in the excretions or secretions .
    • Pulmonary tuberculosis, especially with cavitation.
    • 開放性結核就是在病人咳出的痰液中有結核桿菌的存在
  • Cultures Colonies of M. tuberculosis growing on media
    • Gold standard for TB diagnosis
    • Use to confirm diagnosis of TB
    • Culture all specimens, even if smear negative
    • Results in 4 to 14 days when liquid medium
    • systems used
  • Cultures
    • Sensitivity: 80-85%
    • Specificity: 98%
    • Times needed:
      • Solid medium
        • 4-8 wks
      • Liquid medium
        • 2 wks
  • AFB smear vs. Cultures
    • AFB smear
      • 可檢測到每 ml 標本有 5000-10000 隻細菌
      • 染色陰性並不能排除結核病
      • Rapid diagnosis
    • Cultures
      • 每 ml 標本只需有 10-100 隻細菌便可檢測到
      • More sensitive
      • Allows drug susceptivity test
  • Microscopy is more objective and reliable than X-ray Inter-observer agreement
  • Microscopy is a more specific test than X-ray for TB diagnosis Specificity
  • Diagnosis of Pulmonary TB Cough 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 and evaluation If 2/3 positive : Anti-TB Rx If negative :
  • Diagnosis of pulmonary TB
  • Recommended Diagnostic Approach
  • Take Home Message
    • 診斷結核病必須綜合
      • 臨床表現
        • Non-specific symptoms
      • 放射學變化
        • Often over diagnosis
      • 實驗室細菌學診斷
        • AFB smear
          • Rapid diagnosis, presumptive diagnosis
        • Culture
          • Gold standard, more sensitive
    • 只要強烈懷疑 TB 可先開始進行抗結核治療
  • Source
    • UpToDate, Diagnosis of pulmonary tuberculosis, 2008, John Bernardo,MD
    • 行政院衛生署疾病管制局 , 結核病診治指引 , Taiwan Guidelines on TB Diagnosis & Treatment, Edition 3, 主編陸坤泰
  • Thanks for your attention!