Nearly one in three children and adolescents with insulin-dependent type 1 diabetes have a positive skin test for tuberculosis (TB) and are at risk of developing active TB and spreading the infection to others, according to the results of a study conducted in a TB-endemic area.

It is unclear whether poor blood sugar control predisposes diabetics to developing TB disease following infection, or whether the poor blood sugar control is a consequence of TB disease, the study team notes in the International Journal of Tuberculosis and Lung Diseases.

TB is a highly contagious and potentially deadly infectious airborne disease spread by coughing, sneezing, talking or spitting. Billions of people around the world are infected with TB. Most have latent or dormant infection, meaning they are not infectious, they do not feel sick, and cannot transmit TB to others. However, it's estimated that about 10% of people with latent TB will go on to develop active TB, which is infectious.

For their study, Dr. E. A. Webb, from the Desmond Tutu Tuberculosis Center, Cape Town, South Africa, and colleagues evaluated the prevalence of TB among 258 patients with type1 diabetes who were younger than 21 years old in TB-endemic areas.

The prevalence of TB infection was 29.8%, Webb and colleagues report. Active TB was confirmed in 9 (3.48%) patients, while 16 (6.2%) were previously treated for TB, they observed.

The prevalence of tuberculosis increased from 7.8% at 5 years to 12.5% at 10 years after the diabetes diagnosis, Webb's team reports.

The observed prevalence of tuberculosis among type 1 diabetes was over 6.8 times greater than the population prevalence, the researchers note.

Poor control of diabetes and contact with a tuberculosis source were associated with a 1.39 and 2.78 times higher risk of tuberculosis, Webb's team found.

Routine TB screening of children with type 1 diabetes may be indicated in settings highly endemic for TB, the researchers conclude.

SOURCE: International Journal of Tuberculosis and Lung Diseases, July 2009.

South Africa Medicine