Following phlebotomy (10 ml venous blood), a TST using
2 TU PPD RT 23 (Mantoux PPD, SSI) was placed on the volar
aspect of the left forearm and read within 48–72 h using the
ball-point pen and ruler method. TST reading by the study
nurse was standardised through a large-scale community-based
TST survey. A positive TST was defined as an induration of
>10 mm, in accordance with national guidelines.