1. Caroline Wightman TB Clinical Nurse Specialist The Hillingdon Hospital
TB Diagnosis
Caroline Wightman
TB Clinical Nurse Specialist
The Hillingdon Hospital

2. NW London TB rates per 100,000

3. TB in Hillingdon – Aug 2008

4. TB in NW London by Ethnic Group

5. TB in Hillingdon by Ethnic Group

6. TB in Hillingdon by Age and Sex

7. Summary of Some TB Statistics for NW London in 2008
1111 reported cases
The overall TB incident rate 60.2 per 100,000 population
Brent had highest rate 113.7
Westminster had lowest rate 29.9
Hillingdon had rate of 61.0 (153 cases) a 20.4% increase from 2007 (127 cases)
Ethnic groups
Indian 38% (424 cases)
Black African 27% with 50% from Somalia

8. Summary of Some TB Statistics for NW London in 2008 (cont.)
86% (956 cases) born abroad, 51% (341 cases) entered UK within last 5 yrs.
49% of all cases in NWL in 2008 were pulmonary, of which 31% were sputum smear positive
Multi Drug Resistant TB was identified in 1.3% of cases tested

9. Signs and Symptoms
Cough (with or without haemoptysis) for more than 3 weeks
Most patients report cough for 2 – 3 months
Fevers / temperature (low grade)
Night sweats
Weight loss
Lethargy

10. Medical History History of past TB Past history of TB exposure
When
Length of treatment
Medication used
Past history of TB exposure
Place of birth/ how long in UK
86% of TB patients born abroad
51% of TB patients entered the UK < 5 years

11. Medical History (cont.)
Other chronic medical conditions
Diabetes
Alcohol dependence
Any immunodeficient conditions
HIV infection
History of BCG?
History of recent travel

12. Physical examination To assess patient’s general health Lymph nodes
Cervical, axilla, groin, sub-clavicular
Examination of affected area
Erythema induratum / nodosum

13. Investigations - Respiratory TB
CXR if suspicious for TB should initiate further investigations

14. Investigations - Respiratory TB (cont.)
Multiple sputum samples for AAFB and culture (acid alcohol fast bacilli)
Minimum of 3 (including 1 early morning)
Examine Film/ smear under microscopy on slide
Concentrate sample (auramine)
positive = infectious TB
Liquid culture up to 8 weeks or more

15. Investigations(cont.)
Microscopy
= pot. infectious TB Ref Lab
Concentrate ID & Sensitivities
Culture Ref Lab
8 weeks

16. Investigations Adults Productive cough
spontaneous sputum
Dry cough/ unable to produce sputum
bronchial lavage
induced sputum
Children
Unable to expectorate
Induced sputum (nebulised saline)
Gastric aspirates (early morning via NG tube)

17. Management of Respiratory TB
Treatment should start before culture results are available if clinical picture is consistent with TB
Standard treatment should continue even when culture results are negative
Samples should be sent for culture from autopsy if respiratory TB was suspected

18. Investigations - Non-Respiratory TB
Discuss advantages / disadvantages of biopsy and needle aspiration
Samples for TB culture (dry pot)
Lymph node biopsy
Pus aspirated from lymph nodes
Pleural biopsy
Any surgical sample sent for routine culture
Any radiological sample sent for routine culture
Histology sample
Aspiration sample
Autopsy sample

20. Management of Non- Respiratory TB
Treatment should be started without waiting for culture results if clinical / histological picture consistent with TB
Chest X-ray to exclude co-existing respiratory TB
Continue drug regimen even if culture results are negative

21. Other Diagnostic Aids Diagnostic Molecular Tests
PCR (polymerase chain reaction) detects & amplifies presence of DNA unique to specific organisms
Detects mutations to Rifampicin
Used for rapid confirmation of TB diagnosis in sputum smear positive cases that would alter their care or
Before conducting large contact tracing initiatives
Used infrequently as expensive
Negative PCR does not rule out TB diagnosis

22. Other Investigations (cont.)
Mantoux test (purified protein derivative)
- 2 Tuberculin units by Intradermal injection
- Measured 48 to 72 hours
- Requires 2 visits
- Skilled operator
Main use – contact and new entrant screening
Confounded by BCG vaccine, other Mycobacterium, viral illness, HIV
Negative Mantoux may rule out Sarcoid

23. IFN-γ release assays (IGRA)
ex-vivo immune assay
Previously sensitised T cells exposed to MTb antigens
measure release of IFN-γ

24. IGRA Advantages : Single visit Objective Incorporate controls
Potentially faster
Big advantage: choice of antigen…

25. RD1 contains the genes for ESAT6 and CFP10
M. bovis
M. tuberculosis
RD1 was lost from
BCG early on
RD1 is present in
all strains of
M. tuberculosis
BCG
BCG
ESAT6-early secretory antigen target 6, CFP10 –culture filtrate protein 10

26. Quantiferon Gold In-Tube
1. Take blood into pre-coated tubes (nil, TB antigen, PHA positive control)
2. Incubate at 37°C for hours
3. Centrifuge (15mins, 3000G ~ 3729rpm)
4. Harvest supernatant – can now be stored
5. ELISA at your leisure

27. T-SPOT™.TB (Oxford Immunotec)

28. Summary: IGRAs in Diagnosis
Overall in active disease both IGRAs are more sensitive than TST
Overall in LTBI TSPOT is more sensitive than TST, and QFN is as sensitive as TST
IGRAs are more specific than TST

29. Uses of IGRA IGRA cannot distinguish between active and LTBI
May increase confidence in diagnosis if unable to isolate M.Tb from clinical specimens
False negatives can occur in immunosuppression
Expensive
NICE 2006 suggests 2-step testing with TST in contact tracing, new entrant screening & before immunosuppressive treatment (anti-TNF)

30. Conclusion – Think TB Keep a high index of suspicion
Un-resolving cough
Chronic symptoms (back pain)
Recently arrived in UK from endemic countries - esp. Somalia
Early request for sputum / CXR
If in doubt refer

31. References Health Protection Agency www.hpa.org.uk
Tuberculosis in the UK, Annual Report on Tuberculosis Surveillance in the UK HPA October 2008.
Tuberculosis in North West London Annual Report. Health Protection Agency.
NICE TB Guidance. Clinical Diagnosis and management of Tuberculosis, and measures for its prevention and control. March 2006.
Image source: Core Curriculum on Tuberculosis - What the Clinician Should Know. 4th ed Division of Tuberculosis Elimination, US Centres for Disease Control and Prevention (CDC)