Medscape Medical News (07.28.2013)
Glen S. Hazlewood, MD, and colleagues contend that latent TB infection (LTBI) treatment, such as nine months of isonaizid to prevent TB, before beginning treatment with tumor necrosis factor (TNF) inhibitors might not be necessary for some low-risk elderly patients with rheumatoid arthritis, if these patients’ TB skin tests were 5 millimeters (mm) or smaller, they had no other risk factors, and lived in countries with low TB prevalence.
The researchers created a Markov decision analytic model to estimate outcomes as patients moved between various health states throughout time. They based the model on a hypothetical 65-year-old with a 5- to 9-mm tuberculin skin test (TST), who had not received the Bacille Calmette-Guérin vaccine and had rheumatoid arthritis (RA) and anti-TNF treatment as their only TB risk factors. The researchers reviewed data on the risk of developing active TB for patients from Canada, the United States, France, the United Kingdom, Sweden, and Spain. The researchers sought to determine whether or not to administer isoniazid based on a primary outcome of quality-adjusted life expectancy and a secondary outcome of life expectancy.
The model showed that prophylaxis provided an average gain of 1.1 quality-adjusted life expectancy days and 2.6 days of overall life expectancy. Based on this model, researchers expected 1.4 TB-related deaths per 1,000 patients with prophylaxis and 3.3 deaths per 1,000 patients without it. They also expected 0.2 hepatitis-related deaths per 1,000 with prophylaxis and 0 per 1,000 without it. The decision analysis favored no prophylaxis, based on quality-adjusted life expectancy for elderly patients with low risk of TB reactivation, and prophylaxis for patients with a TST larger than 10 mm or those from a higher-risk country with a TST larger than 5 mm. For overall life expectancy, regardless of preferences, researchers favored prophylaxis.
Joel D. Ernst, MD, from New York University School of Medicine’s Division of Infectious Diseases, noted that researchers limited results to specific types of patients—those with TST results of 5- to 9-mm induration—and that the researchers were not recommending against treatment of LTBI for elderly RA patients in general.
The full report, “Prophylaxis for Latent Tuberculosis Infection Prior to Anti-TNF Therapy in Low-Risk Elderly Patients with Rheumatoid Arthritis: A Decision Analysis,” was published online in the journal Arthritis Care & Research (2013; doi: 10.1002/acr.22063).