We learned in lecture today that of those individuals infected by tuberculosis, only about 10% develop an active TB infection. However, the M. tuberculosis bacteria that infect the remaining 90% become dormant and the affected individual does not develop TB. However, 10% of those with dormant or ‘Latent TB’ can develop Progressive or ‘Secondary’ tuberculosis later on in life.
People that have latent TB can receive treatment through a 6- to 9-month course of isoniazid or rifampin, antibiotics used to kill off M. tuberculosis bacteria in the body.
Unfortunately, according to a massive population study done in the Quebec province of Canada, patients over the age of 65 that are being treated for latent TB have an increased risk of suffering harmful effects from the treatment:
“The five-year study of more than 9,000 residents of Québec province found those patients over age 65…had 2.7 excess hospital admissions per 100 patients compared with matched untreated residents (95% CI 0.1 to 5.3), according to Dick Menzies, MD, of McGill University in Montreal, and colleagues.” (See original article here: http://www.medpagetoday.com/Pulmonology/Tuberculosis/24255 )
Patients of all age groups suffered from adverse events, however the occurrence is most prominent among the elderly.
In order to further investigate the risk of treating older patients with latent TB, Dr. Menzies and his colleagues reviewed administrative data from 1998 to 2003 on all citizens of Quebec who received at least 30 days of treatment for latent TB. The 9, 145 patients who were treated were compared with around 18,000 that did not undergo treatment.
During the 18 month period in which these patients were reviewed, Menzies noted that of the patients who underwent treatment, the rate of hospital admission for treatment-related adverse events (the most common being hepatic events which cause flu-like symptoms) was higher than those that went without the antibiotic series.
For those patients older than 65, the chance of suffering from a hepatic event increased from 0.1% to 2.6%. Also, the odds of hospitalization due to hepatic events for that age group is 6 times greater than other younger patients.
Researchers are now considering if giving treatment to patients older than 65 for latent TB is worth the risk of hospitalization for the adverse events.