Background Several studies have shown that smoking is associated with a higher disease activity and decreased efficacy of anti-tumour necrosis factor-alpha (anti-TNFα) therapy in patients with rheumatoid arthritis (RA)1,2. This is the first study investigating if the same relationship applies to AS patients.
Objectives To compare the efficacy of anti-TNFα therapy in AS patients between ever-smokers and non-smokers.
Methods We conducted a retrospective study on all patients with AS (n=73) commencing their anti-TNFα therapy at Gartnavel General Hospital, Glasgow. 11 patients were excluded from the study due to incomplete data. A total of 62 patients (59.7% males), mean age of 50.6 (SD±12.4), were stratified into 2 groups; ever-smokers (71.0%) (current smokers and ex-smokers) and non-smokers (29.0%). The primary endpoint was the proportion of patients that changed their anti-TNFα drug due to loss of efficacy (LOE) after 1, 2 and 3 years. Secondary endpoints were the proportion of patients that met the ASsessment in AS (ASAS 20) criteria and ASAS 40 by month 6 and 12 respectively.
Results At baseline, there was no significant difference between ever-smokers and non-smokers in Bath AS Disease Activity Index (BASDAI), Bath AS Functional Index, Erythrocyte Sedimentation Rate (ESR), spinal pain, patient global, physician global, Health Assessment Questionnaire (HAQ), C-reactive protein (CRP) and Body Mass Index. There was no difference in the proportion of patients who changed their anti-TNFα drug due to LOE after 1 year (14.0%, 33.3%, p=0.154). However, this proportion was higher in non-smokers than in ever-smokers after 2 (41.2%, 7.5%, p=0.005) and 3 (47.1%, 15.4%, p=0.02) years. There was no statistical difference in the proportion of patients meeting the ASAS 20 (p=0.66) and ASAS 40 (p=0.14) between ever-smokers and non-smokers. However, the ASAS 20 and 40 criteria do not incorporate ESR, CRP and HAQ scores. Ever-smokers had a larger improvement in ESR after 12 months (67.2% improvement in ever-smokers, 8.0% deterioration in non-smokers, p=0.01). Further analysis showed that current smokers improved significantly more than non-smokers in CRP (89.3%, 33.2%, p=0.04) levels after 12 months. HAQ scores (41.1%, 8.0%, p=0.050) after 6 months and ESR (73.0%, 8.0%, p=0.051) levels after 12 months suggested a more significant improvement in current smokers but these failed to reach significance. Smoking less than 5 pack years (current and ex-smokers inclusive) is a positive predictive factor for BASDAI response after 12 months (p=0.04).
Conclusions This is a pilot study investigating the effect of smoking on the effectiveness of anti-TNFα therapy in patients with AS. In our cohort, unlike RA, smoking was suggestive of a positive response to anti-TNFα therapy in patients with AS at 6 and 12 months. However, a study with a larger sample size is recommended to confirm this association.
Söderlin MK, Petersson IF, Geborek P. The effect of smoking on response and drug survival in rheumatoid arthritis patients treated with their first anti-TNF drug. Scand J Rheumatol. 2012 Feb;41(1):1-9.
Hyrich KL, Watson KD, Silman AJ, Symmons DP. Predictors of response to anti-TNF-alpha therapy among patients with rheumatoid arthritis: results from the British Society for Rheumatology Biologics Register. Rheumatology (Oxford). 2006 Dec;45(12):1558-65.
Acknowledgements Sister Janice France, RGN
Samantha Miller, medical student
Disclosure of Interest None Declared