Recognition of a category of responders to group II, slow-grower associated antigens amongst Kuwaiti senior school children, using a statistical model.

A mathematical model previously developed to test the validity of categorisation of skin test responders has been applied to data obtained from 3 age groups of Kuwaiti school children. Two specially designed sets of 4 new tuberculins were tested on senior school children to determine whether extra categories of responders might exist amongst them. Strong statistical evidence has been obtained that a proportion of the children respond to group ii, slow-grower associated antigen, creating a fourth responder category, but no evidence was found for responses to group iii, fast-grower associated antigen. The significance of group ii antigens in immune protection from tuberculosis has never been considered specifically. It is of special interest to note that responders to these antigens have been readily found in Kuwait, a country where BCG is thought to be effective, whereas no such category could be found in India or Sri Lanka, where the efficacy of the vaccine is less certain.