Chest radiographs and TB

Graham Bothamley

Jean-Paul Zellweger

Plan of session

1. The typical chest x-ray of TB

2. Atypical chest x-rays

3. Extrapulmonary TB on the chest x-ray

4. Inactive tuberculosis

5. The normal chest x-ray with C+PTB

6. Differential diagnoses

What are the typical features of tuberculosis on a chest x-ray?

Chest x-rays

Study Under-reading% of positives

Over-reading% of negatives

5 experts 25 -

General 27 1.7

Mass radiography 32 1.7

Danish mass radiography 32 1.6

Reader panel (15,000) 39 1.2

10 best radiologists 21 0.5

10 best physicians 26 0.3

Average 32 2

Improvement only if >20,000 films read annually. Nakamura et al. Kekkaku 1970; 45:121

Conclusions from mass x-ray surveys

• Sudden, symptomatic onset as common as insidious onset

• Disease extent unrelated to duration (extensive S+PTB within first 3-6 m)

• Cavitation is not a late occurrence – its frequency is nearly the same at all temporal stages of the disease

Toman. Case finding and chemotherapy. WHO, Geneva, 1979

Atypical TB

• Lower zone

• No cavitation

• (miliary)

Atypical TB

• Female

• Diabetes

• HIV

• Elderly

Extrapulmonary TB

• Mediastinal lymph nodes

• Pleural effusions

• Paraspinal abscess

• Spinal disease

Pleural effusion

Pericardial TB

TB of the spine

Inactive or self-healed tuberculosis

• Primary focus/calcified granuloma

• Coin lesion

• Fibrosis

The normal chest radiograph with a positive M.tb culture

• Single isolate or repeated?

• Lab contamination – strain typing

• CT scan

• Treat?

Differential diagnosis

• Non-tuberculous mycobacterial disease

• Sarcoidosis

• Fungal disease

M. xenopi

NTMD

• Background of COPD

• Thicker pleural reaction

M. fortuitum

BronchiectasisTree in bud

Nodules

Mycobacterium spp. Runyon group III

The Quiz

Estimate the probability of the diagnosis of tuberculosis and indicate whether you think the person will be sputum smear-positive

• Read the histories and estimate a prior probability of TB

• Look at the CXRs again – in a different order this time and again estimate the probability of TB and whether the sputum smear will be positive

Exercise: 20 CXRsEstimate the probability of TB

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