The prevalence of tuberculosis infection in New South Wales police recruits, 1987-1990.

OBJECTIVE

To determine the prevalence of tuberculosis (TB) infection and to determine the rate of conversion to a positive Mantoux test result after BCG vaccination in a subgroup of the Australian population.

DESIGN

A descriptive and retrospective study.

SETTING

The Police Academy, Goulburn, New South Wales.

PARTICIPANTS

4704 recruits to the New South Wales Police Service between 1987 and 1990.

MAIN OUTCOME MEASURES

Rates of positive Mantoux test results before and after administration of BCG.

RESULTS

Eleven per cent of Police Cadets were Mantoux positive. Of those who had never been vaccinated with BCG, 7% were positive. Statistically significant differences in Mantoux positivity were found in relation to age, sex and country of birth. There was also a significant difference in the frequency of positive Mantoux reactions between the group vaccinated with BCG at the Academy and those who were vaccinated earlier in life.

CONCLUSIONS

Routine Mantoux testing of population subgroups provides a useful source of information on the prevalence of TB infection. However, without testing for the "booster phenomenon" only a minimum estimation of the infection rate can be determined. The National Health and Medical Research Council recommendation that a Mantoux reaction of 5-9 mm be considered positive in the southern States of Australia is supported. The low rate of conversion to a positive Mantoux test result after administration of BCG vaccine at the Police Academy indicates that Mantoux testing after vaccination is not useful.