The aim of this work is to study the prevalence of mycobacterial infection (M.I.), the associated factors and their clinical significance in patients included in a large SLE cohort.
Methods Retrospective descriptive study of RELESSER patients with a history of M.I. and analysis of the factors associated with the infection of this aetiology.
Results In RELESSER 3,658 SLE patients were included. 90% women, mean age of 32.9 years. 93% Caucasians. The mean follow-up time (±S.D.) was 120.2 (±87.6) months. 705 (19.3%) patients had at least a serious infection, 1227 serious infections occurred. M.I. were diagnosed in 42 patients (1.2% of all RELESSER patients, 3.4% of all serious infections), 85.7% women. The incidence rate of mycobacterial infection was 1 per 1000 patients/year (95% CI: 0.7 to 1.4).
M.I. presentation was pulmonary in 18 (42.9%) patients and extrapulmonary in 24 (57.1%)patients:joints in 8 (19.0%) patients, soft tissue in 6 (14.3%) and other sites in 10 (23.8%). The extrapulmonary form was associated with the use of immunosuppressants: 84.6% of the 13 patients treated with immunosuppressive drugs versus 44.4% of the 27 patients without (p=0.01). We did not observe this association with the use of corticosteroids.
To study the factors associated with mycobacterial infection, we performed a bivariate analysis including the variables associated with severe infection identified in RELESSER (age, sex, ethnicity, use of corticosteroids, immunosuppressants, antimalarials, previous admission by SLE activity, use of rituximab, use of anti-TNF, Katz severity index, SDI damage index, SLEDAI activity index and Charlson comorbidity index). There is a statistically significant association with previous admission by SLE activity (RR: 2.9,95–95% CI: 1.3 to 6.2, p=0.007), renal impairment (RR:2.0, 95% CI: 1,1 to 3,7, p=0,04), the Katz score (RR: 2.1, 95% CI:1.1–4.0,p=0.04) and the Charlson index (RR: 2.5; 95% CI: 1.3 to 4.8, p=0.009). The accumulated damage (SDI>0) was closely associated with significance: RR: 2.0; 95% CI: 1.0 to 4.0, p=0.07. The use of immunosuppressants was associated with a significant increase in the risk of mycobacterial infection: RR: 4.3; 95% CI: 2.2 to 8.3, p=0.31.
Two patients (4.8%) died (1respiratory and 1extrapulmonary). The mean survival after diagnosis in these cases was 21 days.
Conclusion M.I. in RELESSER affects 1.15% of patients. Its incidence rate is 1 per 1000 patients/year (95% CI: 0.7 to 1.4). Extrapulmonary localization affects more than half of the patients and is associated with the use of immunosuppressants. Previous admission by SLE activity, renal involvement, severity of SLE, and increased number of associated comorbidities are factors associated with the existence of mycobacterial infection.
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