Risk of active tuberculosis among COPD patients treated with fixed combinations of long-acting beta2 agonists and inhaled corticosteroids

Tuberculosis (TB) is a serious public health problem in many countries, including Taiwan [1‐6]. In addition to the use of appropriate anti-TB treatment, early detection in vulnerable populations is an important way of preventing its spread [7]. Many well-known risk factors, including HIV infection, diabetes mellitus, socioeconomic status, alcoholism and immunocompromised condition have been reported as being significantly associated with TB [8‐10]. In addition to these risk factors, many studies have shown that the use of corticosteroids, in both systemic and inhaled forms, can also increase a patient’s risk of TB [11‐15]. Regarding the association between inhaled corticosteroid (ICS) and TB, one meta-analysis of 25 trials by Dong et al. showed ICS treatment was associated with a significantly higher risk of TB (Peto OR, 2.29; 95% CI, 1.04–5.03, 14) and another meta-analysis of nine non-randomized studies by Castellana et al. showed that any ICS use was associated with an increased risk of TB versus no ICS use (OR = 1.46; 95% CI 1.06 to 2.01). and a similar trend was also found for current ICS use versus prior/no ICS use, as well as for high, moderate and low ICS dose versus no ICS [15].

However, ICS are a major treatment component for patients with chronic obstructive pulmonary disease (COPD), and the combination of inhaled long-acting β2-agonists (LABAs) and ICSs has been shown to be effective for the reduction of COPD exacerbations [16‐18]. Although many LABA/ICS combinations have been developed, clinical experience using budesonide/formoterol and fluticasone/salmeterol, as well as associated studies, are most plentiful because these two combinations were developed earliest. Recently, several studies have revealed safety differences between fluticasone/salmeterol and budesonide/formoterol [19‐21]. These studies found that fluticasone/salmeterol users have a higher risk of pneumonia, sepsis, and death compared with budesonide/formoterol users [19‐21]. However, no study has previously compared the risk of TB between fluticasone/salmeterol and budesonide/formoterol. Therefore, the current study investigated the incidence of active TB among COPD patients using fluticasone/salmeterol and budesonide/formoterol, and to see if there were any differences between these two groups.

The present national population-based study demonstrated that COPD patients receiving fluticasone/salmeterol had a higher risk of active TB compared with those receiving budesonide/formoterol. In contrast to previous meta-analyses [14, 15] showed that ICS increased the risk of tuberculosis, this study is the first one to point out patients using fluticasone/salmeterol are at higher risk of tuberculosis then patients using budesonide/formoterol. This significant difference between budesonide/formoterol and fluticasone/salmeterol was confirmed in various populations, including intention-to-treat and after propensity score matching methods and competing risk analysis. This trend was also observed in the as-treated population with nearly the same proportion using different methods. However, the non-significant difference could be due to the low case number in as treated analysis. Even in the subgroup analysis, the fluticasone/salmeterol group remained associated with a higher risk of active TB compared with the budesonide/formoterol group. This intra-class difference has been shown in a previous study [21], and there may be different risks for other infectious diseases between budesonide/formoterol and fluticasone/salmeterol. In the PATHOS study, the rate of pneumonia and the pneumonia event rate per 100 patients were higher in fluticasone/salmeterol compared with budesonide/formoterol [19]. Another study showed that fluticasone/salmeterol carried a higher risk of sepsis (aHR, 1.15; 95%CI, 1.07–1.24) and septic shock (aHR, 1.14; 95%CI, 1.01–1.29) compared with budesonide/formoterol [21]. However, the present study is the first to confirm an intra-class difference for the risk of active TB between fluticasone/salmeterol and budesonide/formoterol. Therefore, these findings confirmed the significant differences between budesonide/formoterol and fluticasone/salmeterol in terms of the risk of infectious diseases, including TB, in patients with COPD.

As this study was an observational cohort study, it was not possible to investigate the possible mechanisms that caused the differences between fluticasone and budesonide. However, several different pharmacologic characteristics between these two agents may give some explanations. First, the uptake and elimination rates are slower for fluticasone than budesonide, as reported in a previous pharmacokinetic study [23]. The mean residence time of budesonide was shorter than fluticasone, and the amount of expectorated fluticasone was significantly higher compared with budesonide [24]. Second, fluticasone and budesonide also differ in the immune response that they influence. In vitro studies have shown that fluticasone is about 10 times more potent than budesonide in inhibiting the release of IL-6, IL-8, and TNF-α production [25]. Third, budesonide is less lipophilic than fluticasone. In summary, all of these factors suggest that fluticasone can reside in humans for longer and could cause a more potent immunosuppressive effect than budesonide, thereby facilitating TB infection.

The present study had two major strengths. First, it was conducted using data from the NHIRD database, which includes nearly all patients in Taiwan. Using this database, it is possible to enroll a large population and obtain long-term follow-up data for the included subjects. Therefore, the findings can be considered representative and truly reflective of the real-world. Second, TB remains prevalent in Taiwan, and the incidence of TB in Taiwan is much higher than in Western countries. Therefore, the cohort contained a large number of TB cases, which can help increase the statistical power of the analysis for subgroup and confounding factor adjustment. Nevertheless, the current study had several limitations. First, although many variables were collected to minimize the confounding effect, the effect of some potential confounder, such as BMI, pulmonary function, the status of smoking and history of latent TB, data for which was not available in the NHIRD database. However, the status of smoking and latent TB could have significant impact on the development of active TB. Further study is warranted to assess their effect on the risk of TB. Second, microbiological data is lacking in the NHIRD database, however, this data is the key diagnostic criteria for active TB. To overcome potential misclassification of TB in the claims database, cases of active TB were only identified when they had concurrent ICD-9 codes for TB and a history of anti-TB medication. Third, the effect of dose and duration of LABA/ICS was not assessed in this study.

Fluticasone/salmeterol carried a higher risk of active TB than budesonide/formoterol among COPD patients.