Article Text


Interferon-gamma assays in TB diagnosis
P18 How effective is the recommended staging for latent TB follow-up?
  1. D Thomas,
  2. M Jarvis,
  3. A Williams
  1. Royal Bournemouth Hospital, Bournemouth, UK


Introduction NICE (2011) recommends that patients with latent TB infection who are eligible for but decline treatment are followed up with a chest x-ray (CXR) at 3 and 12 month intervals to assess for TB reactivation. The aim of this study was to assess the effectiveness of this strategy in detecting reactivation of TB.


  • A retrospective case note analysis of 146 latent TB patients (2006–2011) of all ages.

  • Mode age range 16–35 (46%).

  • Follow-up attendance, clinical presentation, CXR appearances and patient demographics were recorded.


  • 47% (n=69) attended for follow-up at 3 and 12 months.

  • 18% DNA at 3 months, 35% DNA at 12 months. 13% moved away.

  • 98.6% of patients showed no evidence of TB reactivation in a 12-month period.

  • 52% of patients were under 35.

  • 2 (1.4%) patients developed active TB within a 12-month period. One was found to have CXR changes at the 3-month follow-up, and was later admitted with TB meningitis. The other was symptomatic (no CXR changes) and was treated empirically for active TB.

  • 63% were new entrants; 41% had been in the UK <1 year.

  • 1 patient was immunosuppressed.

  • Common risk factors for LTBI were ethnicity (73%) and occupational exposure (19%). Only 12% recalled previous TB contact.


  • 3 and 12-month follow-up had a very low yield of detecting TB reactivation in this sample (1.4%).

  • It cost £16 000 (based on current PbR tariff) to screen the 69 patients who attended at 3 and 12 months.

  • Use of limited resources must be justified. Are there better staging intervals for follow-up?

  • Follow-up is also associated with a high DNA rate, particularly at 12 months, further stretching resources.

  • However, follow-up allows health promotion regarding TB symptoms and the role of chemoprophylaxis.

Conclusion These results question the validity of following up LTBI patients at 3 and 12 months after diagnosis. Further longitudinal studies are needed to determine the optimum intervals for follow-up.

Abstract P18 Figure 1

Effectiveness of latent TB follow-up.

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