Aim NICE Guidance (2016) recommends that TB contact screening is only carried out on close contacts (household and workplace/school contacts) of patients with infectious tuberculosis ie pulmonary tuberculosis (AFB smear positive) and laryngeal tuberculosis. However previous guidance recommended screening all household contacts of any index with TB irrespective of infectious status. The aim of this study was to look at the yields of contact screening amongst 3 groups of index cases- infectious smear positive pulmonary TB, smear negative pulmonary TB and extrapulmonary TB.

Method We analysed our records for contact screening of index cases with tuberculosis notified between January 2011 and May 2016. Index cases were divided into pulmonary smear positive, pulmonary smear negative and extrapulmonary. Contacts were divided into close, casual and workplace. The screening yields for each population were compared.

Results Between 1 st January 2011 and 31 st May 2016 1887 contacts of 408 notified index cases with TB were screened; 1109 were screened as contacts of smear positive pulmonary TB, 176 contacts of smear negative pulmonary TB, 506 contacts of extrapulmonary TB, the remainder the index site of disease was not specified. CXR screening was performed on the 510 contacts over the age of 35 (2011 guidelines). Patients 35 and under had 2 step immunological assessment with Mantoux and IGRA. There was a strong correlation between size of Mantoux response and IGRA positivity; 6% of Mantoux <6 mm, 23% Mantoux 6–10 mm, 40% Mantoux 11–15 mm, 55% Mantoux 15–20 mm, 84% Mantoux ≥25 mm. 604 contacts of index cases with AFB smear positive sputum were assessed immunologically – 123 (20.3%) were positive, 136 contacts of AFB smear negative pulmonary TB were assessed – 19 (10.5%) were positive, and 383 contacts of extrapulmonary TB were assessed – 42 (11%) were positive. 26 of 239 (11%) workplace/school contacts of infectious TB were positive, compared to 21.5% of close/casual contacts.

Conclusions Although contact screening yields for index cases with smear positive pulmonary TB are high, the Results for extrapulmonary and smear negative pulmonary TB are not insubstantial. Our data would suggest that we should continue screening close contacts of all TB index cases irrespective of infectious status.