【正确答案】The clinical significance of a positive tuberculin skin test including ⑴indicate reactivity after BCG vaccination（1分） ⑵For asymptomatic older children , positive reactivity indicates infection with tuberculosis in the past.（1分） ⑶For infants, especially for those who have not received a BCG vaccination, a positive reactivity indicates a new tuberculous lesion. （1分） ⑷A strong positive reactivity indicates an active infection with tuberculosis. （1分） ⑸Reactivity change from negative to positive , and increment >6mm indicates a recent infection with tuberculosis. （1分）