[Booster effect in elderly patients living in geriatric institutions]

Tuberculinic response is weaker in elderly patients. To know the real tuberculinic reactivity in elderly patients living in geriatric institutions in Catalonia, Spain, and to reduce the probability of false negatives this study was carried out to detect the booster effect.

Three hundred forty-three individuals with a mean age of 81 +/- 6.5 years, residing in four geriatric centers within the Central Health Care Region of Catalonia, were studied. After performing the first Mantoux intradermoreaction this was repeated at one week in case of negativity. A third test was carried out after one more week on persistence of negativity. Qualitative study was carried out on cell immunity in those patients whose first Mantoux test was negative.

The first Mantoux test was positive in 163 patients (47.5%) and the performance of the second and third test in cases of negativity of the previous test increased the number of positivities by 12.5% and 4.1%, respectively, up to a total of 220 patients (64%). In the patients who did not react to the first intradermoreaction and who preserved cell immunity a booster effect was obtained in 57 (52.8%). The prevalence of tuberculous infection in this group of elderly patients calculated in the group with preserved cell immunity was 81.2% while the morbidity of tuberculous disease in the positive cases in the Mantoux test was 1.8%.

Given the high frequency of the booster effect in elderly people, systematic testing is recommended to investigate tuberculinic reactivity in patients who are initially negative on Mantoux intradermoreaction.