November 28, 2011 — A long-term, large-scale investigation supports the hypothesis that autoimmune disorders elevate the risk for pulmonary embolism (PE), according to a report published online November 26 in the Lancet.
Bengt Zöller, MD, from Lund University in Malmö, Sweden, and colleagues used the MigMed2 database to calculate standardized incidence ratios for subsequent PE in patients admitted to the hospital for autoimmune disorders from January 1, 1964, to December 31, 2008. The analysis considered the time from the admission for the autoimmune disorder to the PE, and excluded patients with preexisting venous thromboembolism. The reference population was the entire general Swedish population, which is included in the database.
The inflammation that is part of autoimmunity could drive venous thrombosis. Previous studies have linked increased risk for venous thrombosis to celiac disease, type 1 diabetes mellitus, systemic lupus erythematosus, hyperthyroidism, rheumatoid arthritis, inflammatory bowel disease, Behçet's disease, and Wegener's granulomatosis. The study greatly extends the number of autoimmune disorders evaluated for PE risk.
The analysis revealed a strong association between hospital admission for an autoimmune disorder and PE during the subsequent year. For the 535,538 patients admitted for an autoimmune disorder, the overall risk for PE in the first year after admission was 6.38 (95% confidence interval [CI], 6.19 - 6.57). Both sexes and all ages had the elevated risk, which held up for all 33 autoimmune disorders considered, but 4 demonstrated a particularly strong association: immune thrombocytopenic purpura (standardized incidence ratio [SIR] adjusted for age, sex, time, and comorbidity was 10.79; 95% CI, 7.98 - 14.28), polyarteritis nodosa (SIR, 13.26; 95% CI, 9.33 - 18.29), polymyositis or dermatomyositis (SIR, 16.44, 95% CI, 11.57 - 22.69), and systemic lupus erythematosus (SIR, 10.23; 95% CI, 8.31 - 12.45). Two common autoimmune diseases also had high associations: rheumatoid arthritis (SIR, 5.99; 95% CI, 5.59 - 6.41) and type 1 diabetes mellitus (SIR, 6.38; 95% CI, 3.28 - 11.18).
The elevated overall risk for PE fell over time, from 1.53 (95% CI, 1.48 - 1.57) at 1 and5 years, to 1.15 (95% CI, 1.11 - 1.20) at 5 to 10 years, and 1.04 (95% CI, 1.00 - 1.07) at 10 years and later. The researchers conclude that 33 autoimmune diseases "were associated with significantly increased risks of pulmonary embolism during the first year after admission. Our findings suggest that hypercoagulability is a general feature of most autoimmune disorders."
A study limitation is that considering only hospital admissions might exclude less severe cases of the autoimmune disorders. The database did not include general cardiovascular risk factors, but the investigators adjusted for 10 comorbid conditions. Still, the researchers conclude that the associations are strong enough to warrant consideration of autoimmune disorders as hypercoagulation disorders.
In an accompanying comment, Carani B. Sanjeevi, MD, PhD, from the Karolinska Institute in Stockholm, Sweden, recommends that prospective studies investigate the use of inflammatory markers to identify patients with autoimmune disorders who might benefit from prophylactic use of antiinflammatory agents, perhaps with antithrombolytic agents, to prevent PE.
The study was supported by the Swedish Research Council, the Swedish Council for Working Life and Social Research, the Swedish Research Council Formas, and Region Skåne. The authors and commentator have disclosed no relevant financial relationships.
Lancet. Published online November 26, 2011. Study abstract Editorial extract
Bengt Zöller, MD, from Lund University in Malmö, Sweden, and colleagues used the MigMed2 database to calculate standardized incidence ratios for subsequent PE in patients admitted to the hospital for autoimmune disorders from January 1, 1964, to December 31, 2008. The analysis considered the time from the admission for the autoimmune disorder to the PE, and excluded patients with preexisting venous thromboembolism. The reference population was the entire general Swedish population, which is included in the database.
The inflammation that is part of autoimmunity could drive venous thrombosis. Previous studies have linked increased risk for venous thrombosis to celiac disease, type 1 diabetes mellitus, systemic lupus erythematosus, hyperthyroidism, rheumatoid arthritis, inflammatory bowel disease, Behçet's disease, and Wegener's granulomatosis. The study greatly extends the number of autoimmune disorders evaluated for PE risk.
The analysis revealed a strong association between hospital admission for an autoimmune disorder and PE during the subsequent year. For the 535,538 patients admitted for an autoimmune disorder, the overall risk for PE in the first year after admission was 6.38 (95% confidence interval [CI], 6.19 - 6.57). Both sexes and all ages had the elevated risk, which held up for all 33 autoimmune disorders considered, but 4 demonstrated a particularly strong association: immune thrombocytopenic purpura (standardized incidence ratio [SIR] adjusted for age, sex, time, and comorbidity was 10.79; 95% CI, 7.98 - 14.28), polyarteritis nodosa (SIR, 13.26; 95% CI, 9.33 - 18.29), polymyositis or dermatomyositis (SIR, 16.44, 95% CI, 11.57 - 22.69), and systemic lupus erythematosus (SIR, 10.23; 95% CI, 8.31 - 12.45). Two common autoimmune diseases also had high associations: rheumatoid arthritis (SIR, 5.99; 95% CI, 5.59 - 6.41) and type 1 diabetes mellitus (SIR, 6.38; 95% CI, 3.28 - 11.18).
The elevated overall risk for PE fell over time, from 1.53 (95% CI, 1.48 - 1.57) at 1 and5 years, to 1.15 (95% CI, 1.11 - 1.20) at 5 to 10 years, and 1.04 (95% CI, 1.00 - 1.07) at 10 years and later. The researchers conclude that 33 autoimmune diseases "were associated with significantly increased risks of pulmonary embolism during the first year after admission. Our findings suggest that hypercoagulability is a general feature of most autoimmune disorders."
A study limitation is that considering only hospital admissions might exclude less severe cases of the autoimmune disorders. The database did not include general cardiovascular risk factors, but the investigators adjusted for 10 comorbid conditions. Still, the researchers conclude that the associations are strong enough to warrant consideration of autoimmune disorders as hypercoagulation disorders.
In an accompanying comment, Carani B. Sanjeevi, MD, PhD, from the Karolinska Institute in Stockholm, Sweden, recommends that prospective studies investigate the use of inflammatory markers to identify patients with autoimmune disorders who might benefit from prophylactic use of antiinflammatory agents, perhaps with antithrombolytic agents, to prevent PE.
The study was supported by the Swedish Research Council, the Swedish Council for Working Life and Social Research, the Swedish Research Council Formas, and Region Skåne. The authors and commentator have disclosed no relevant financial relationships.
Lancet. Published online November 26, 2011. Study abstract Editorial extract
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