Patients with HIV who had positive tuberculin skin tests had a reduced risk for tuberculosis after receiving isoniazid preventive therapy, according to results from a study in Brazil.
“Our data suggest that a 6-month regimen of [isoniazid preventive therapy (IPT)] is sufficient to reduce TB risk as long as 7 years, but failing to complete the IPT regimen may yield high TB risk,” the researchers wrote in Clinical Infectious Diseases. “Better operationalizing of IPT for people with HIV in Brazil is imperative to help curb TB risk, as too few patients are receiving these beneficial treatment.”
Jonathan E. Golub, PhD, associate professor in the Center for Tuberculosis Research at Johns Hopkins University School of Medicine, and colleagues evaluated TB rates among patients in the TB/HIV in Rio (THRio) study who had positive tuberculin skin tests (TST). The analysis included 1,954 patients with positive TST and a median follow-up of 4.7 years from IPT initiation.
Eighty-two percent of patients started IPT. There were 127 first TB episodes diagnosed within the follow-up period, for an incidence rate of 1.39 per 100 person-years. There were 86 TB episodes among patients who never received IPT, an incidence rate of 6.52 per 100 person-years. Among those who initiated IPT, there were 41 TB episodes, for an incidence rate of 0.53 per 100 person-years.
In a multivariate analysis, IPT initiation was associated with an 83% reduction in TB risk (HR=0.17; 95% CI, 0.11-0.25). Taking ART was associated with a 31% reduced risk for TB (HR=0.69; 95% CI, 0.48-1). A CD4 count of no more than 200 cells/mcL was associated with an increased TB risk. Sex and age were not associated with TB risk.
“When we plot TB risk by IPT initiation, we clearly see that TB risk remains low over 7 years for those receiving IPT,” the researchers wrote. “Among the cases of TB that developed among those who completed therapy, 16% occurred in the year following initiation and among those who did not complete treatment, 38% of TB cases were diagnosed in this time frame. While we cannot rule out reinfection in these patients, our results suggest lack of cure of infection was the more likely reason for these TB events, while reinfection may have been the cause for later events.
Disclosure: The researchers report no relevant financial disclosures.