[Tuberculous infection in the province of Las Palmas (1990-1993)]

The objective of this study was the study of the parameters of tubercular infection (prevalence and RAI) arising from tuberculin surveys of the school-age population.

A descriptive study of a crossover type, looking at each school year.

The surveys were carried out among the entire school population (n = 10,711) of all the public and private schools in Las Palmas.

The population under study was a representative sample of first-year EGB students (age 6-7) of the 1990-91 (n = 1,951), 1991-92 (n = 2,505) and 1992-93 (n = 2,208) school intakes. There was a "no authorisations" index of 35%, 25% and 33.2%, respectively. The sample selection was made each year, in a random manner per conglomerates, after previous stratification by geographical areas. The sample unit was those schools with over 45 pupils per class, distributed throughout the province of Las Palmas. The confidence level for overall data was 95.5% and the margin of error +/- 2.

The tuberculin tests were performed by specifically contracted and trained doctors and DUE (nurses) at Health Centres, belonging to Primary Care and town councils. The technique used for the tuberculin survey was the intradermal injection of 0.1 ml of PPD which contained 2 units of PPD-RT 23 with Tween-80, with a reading at 72 hours, when a reaction of 5 mm or over was considered positive. To calculate RAI the formula proposed by Styblo was used.

The prevalence of tubercular infection in the province of Las Palmas was 0.71% (0.52-0.90) in 1990 and 1.18% (0.75-1.61) in 1993. RAI was 0.11% in 1990 and 0.18% in 1993.

It was almost impossible to make any comparisons with other similar studies because of the lack of homogeneous criteria. Both the prevalence and the risk of tubercular infection in Las Palmas between 1990 and 1993 show an upward tendency.