Association between immunosuppressive therapy and relative risk

Published Date: 19th July 2016

Publication Authors: Dawson J

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Background

RA is associated with clinically relevant interstitial lung disease (ILD) in around 5% of patients. A variety of immunosuppressive agents have been advocated in patients with RA-ILD, with very little evaluation of their comparative effectiveness. We have examined the influence of a range of immunosuppressives (ISP) on mortality in a large multi-centre group of patients retrospectively to determine any effect of these agents on relative risk of death.

Methods

For the purposes of this study, we collected data from seven centres across the UK on patients with both RA and ILD (proven on HRCT) identified over a 12 year period from 2000 to 2012 using a standard proforma. We analysed the age, duration of both RA and ILD, outcome and, where appropriate, cause of death. Equivalent data were obtained from a control group of RA patients from one  centre without lung disease, matched for age, sex and disease duration. We recorded the number of patients receiving ISP. We compared all cause and respiratory mortality between RA controls, all patients with RAILD, and those receiving immunosuppressives. We calculated the influence of each agent on the relative risk of dying from any cause, and from lung disease, compared with RA controls.

Results

A total of 188 patients were identified from across the UK with proven RA-ILD which carried increased relative risks (RR) of death from any cause [1.55 (1.1-2.0)] and from lung disease [1.90 (0.9-3.9)]. Among these, 83 received ISP therapy compared with 27 controls in the RA group. The effects of ISP on RR are shown in Table 1.

Conclusion

Patients with RA-ILD have increased mortality compared with controls. They are more likely to receive immunosuppressive therapy. It is impossible to confidently attribute excess mortality to the use of specific drugs, as thresholds for their use differ. However, this large retrospective multi-centre study suggests a possible survival advantage in treating these patients with MMF or tacrolimus, as opposed to traditional therapy with AZA, especially in terms of their respiratory mortality. This theory could be tested in a large prospective study.

Janakiraman, G; Dawson, J et al. (2014).  RA-related interstitial lung disease: Association between immunosuppressive therapy and relative risk of death . Rheumatology. 53 (Suppl 1), i102-103.

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