Pulmonary TB Flashcards
Epidemiology of TB
-Mycobacterium tuberculosis is the predominant pathogen in humans
-One third of world’s population have latent TB
-In the UK tuberculosis incidence ~10 per 100,000
-International problem accounting for
2-3 million deaths per year
Risk factors for TB
-TB contact- 1 in 3 risk if household
contact
-Very young + Elderly
-Lived in, travel to or receive visitors
from TB endemic countries
-Ethnic minorities
-Malnutrition, Alcoholism, Social
deprivation
-Immunosuppression
HIV anti-TNFa
chemotherapy
-Health care worker
-Silicosis
-Old untreated tuberculosis on the
chest radiograph
Differences in TB infection based on ethnicity
-Black African
-Pakistani
-Indian
-White
Site of TB infection
-Pulmonary tuberculosis
=Remains the commonest form in both HIV positive and negative patients (60-70%)
-Pleural, lymph node and bone tuberculosis
Symptoms of TB
- Several weeks/months
- Weight loss
- Night sweats
- Cough
- Can be productive +
haemoptysis - Anorexia
- General malaise
Indications of active TB on chest radiograph
-Soft nodular shadowing
-Consolidation
-Infiltration
-Cavitation
-Miliary (<5mm nodules)
-Pleural effusion
-Tuberculoma
=Upper lobes predominate
=Can be widespread
Investigations of TB
-Chest radiograph
-Tuberculin skin test (Mantoux test- read at 48-72 hours)
-Interferon gamma release assay
-Neither
Describe the Mantoux test
-0-5mm= -ve or fulminant TB
-6-14mm= immune
->/15mm= TB infection, active TB, strong BCG reaction
Describe IFNy assays
-Use of TB specific antigens
early secretion antigen target 6 (ESAT 6)
culture filtrate protein 10 (CFP 10)
-It is therefore absent from BCG and the majority of
environmental bacteria
-NICE Guidelines recommend Mantoux
if +ve to then proceed with IFN g if available
Samples of pulmonary TB
-Sputum x3
-Induced sputum x3
-Broncho-alveolar lavage +/ TBB
-Early morning urine
-Gastric lavage
-Blood cultures
TB tests
-Smear (1-2 days)
-TB culture (6-8 weeks)
-Histopathology (up to 1 week)
Molecular probes vs Smear
-Molecular probes may be more sensitive and specific compared with conventional acid-fast staining methods
-Individual species of mycobacterium can be identified directly and rapidly from the sample
-Expensive
Histology appearance
-Central caseating necrosis
Actions for inpatients
-Isolate preferably -ve pressure room
-3 sputum samples for ZN stain + routine culture + TB culture
-Refer TB team
What not to do for TB inpatients
-Don’t keep in open ward
-Don’t ask physiotherapists to get sputum from patient in open ward
-Don’t do IGRAs, EMU for TB culture
-Don’t start TB treatment until guided by TB scan
