medwireNews: Screening for and treatment of latent tuberculosis (TB) infection are important preventive strategies in people receiving biologic therapies for rheumatic diseases, irrespective of the drug class, South African researchers report.
Clive Pettipher (South African Rheumatism and Arthritis Association, Stellenbosch) and Romela Benitha (Wilgeheuwel Hospital, Johannesburg, South Africa) found that the rate of TB was 2.0% among 4830 people using biologics for the treatment of rheumatic diseases. Of the 96 TB cases, 62.5% were pulmonary and 37.5% were extra-pulmonary.
Just under half (46.9%) of the TB cases were reactivations, defined as TB diagnosed within 18 months of starting a biologic, while the remaining 52.1% were new infections, defined as TB cases diagnosed after at least 18 months of biologic treatment.
The overall rate of TB among biologic users was 1240 cases per 100,000 person–years, compared with 0 per 100,000 person–years in a cohort of 152 biologic-naïve patients with rheumatic diseases, giving a significant incidence rate difference of 0.0124.
The researchers report in the Annals of the Rheumatic Diseases that TB occurred in patients receiving each of the seven biologics licensed in South Africa, with the highest rate observed among those using monoclonal TNF inhibitors (infliximab, adalimumab, or golimumab), followed by etanercept and non-TNF inhibitors, at rates of 1683, 861, and 681 per 100,000 person–years, respectively.
Monoclonal TNF inhibitors were associated with a significantly higher rate of TB than both etanercept and non-TNF inhibitors, at incidence rate ratios of 1.96 and 2.47, respectively, but there was no significant difference between etanercept and non-TNF inhibitors.
Among the specific treatments, the rates were 2160, 1625, and 1099 TB cases per 100,000 person–years with infliximab, adalimumab, and golimumab, respectively, and 916, 754, and 498 cases per 100,000 person years with abatacept, tocilizumab, and rituximab, respectively.
The majority (98.3%) of patients included in the study underwent screening for latent TB infection, with 12.9% having a positive result. Of these, 14 developed TB infection, including 13 who had received isoniazid/rifampicin treatment. There were nine cases of reactivation TB in this group, which the researchers say indicates treatment failure.
In addition, 33 of the 77 people who had a negative screening result developed reactivation TB, which suggests screening failure in these patients. Pettipher and Benitha suggest that these failures could be due to “[p]oor intradermal injection technique, inaccuracies in reading the [tuberculin skin test] and under-reporting of granulomas on [chest X-ray].”
The investigators conclude: “All biologics increase the risk of TB, especially monoclonal inhibitors, but importantly also non-TNF inhibitors with a risk not statistically different to etanercept.”
They add: “A limitation of this study is that our registry data capture the economically advantaged who have the least exposure and risk of developing TB and cannot be extrapolated to the general rheumatology population.
“Even in this privileged cohort however, the risk of TB remains high.”
And the team recommends: “Risk stratification, screening and treatment for [latent TB infection] are important mitigating strategies in preventing TB infection.”
By Laura Cowen
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