title: Increased susceptibility to infections before the diagnosis of immune thrombocytopenia.
abstract: BACKGROUND
  Infections after diagnosis of primary chronic immune thrombocytopenia (cITP) have mostly been connected to the immunomodulation treatment. Infections may trigger autoimmune diseases and may be a complication of an already impaired immune system.
  
  
  OBJECTIVE
  To investigate the association of cITP with infection before diagnosis. We also estimated the incidence of cITP based on the new definition by the International ITP Working Group.
  
  
  METHODS
  We identified 1087 adults with primary cITP between 2006 and 2012 using the Swedish Patient Register. Data on infections not already associated with secondary ITP were also retrieved from the register. The standardized incidence ratios (SIRs), using the rates from the general population, and 95% confidence intervals (CIs) were estimated as a measure of relative risk. We used data from the Prescribed Drug Register to estimate SIR for anti-infective treatment.
  
  
  RESULTS
  The incidence of cITP was 2.30 per 100 000 person-years (95% CI, 2.15-2.45). cITP was associated with an increased risk of serious infections requiring inpatient or outpatient care within 5 years before cITP diagnosis (SIR = 8.74; 95% CI, 7.47-10.18). Higher magnitude SIRs were observed for candidiasis, viral infection at an unspecified site and acute upper respiratory infections. For anti-infective drugs the SIR was 1.37 (1.25-1.50) and the highest SIRs were observed for amoxicillin, macrolides, nitrofurantoin and antivirals.
  
  
  CONCLUSIONS
  Patients with cITP have increased risks of infection and anti-infective treatments before their cITP diagnosis, with a more marked risk for candidiasis and viral infections. The findings indicate that infection is not only related to the immunomodulation treatment but also to the disease itself.
authors.affiliation: Centre for Pharmacoepidemiology, Department of Medicine, Karolinska Institutet, Solna, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Ekstrand
authors.affiliation: Centre for Pharmacoepidemiology, Department of Medicine, Karolinska Institutet, Solna, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Linder
authors.affiliation: Department of Medical Science Hematology, Uppsala Universitet, Uppsala, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Cherif
authors.affiliation: Centre for Pharmacoepidemiology, Department of Medicine, Karolinska Institutet, Solna, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Kieler
authors.affiliation: Centre for Pharmacoepidemiology, Department of Medicine, Karolinska Institutet, Solna, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Bahmanyar
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D015331:Cohort Studies; D004198:Disease Susceptibility; D005260:Female; D006801:Humans; D007107:Immune System; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D015994:Incidence; D007239:Infections / Q000150:complications* / Q000453:epidemiology / Q000209:etiology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000150:complications* / Q000453:epidemiology / Q000209:etiology; D012042:Registries; D012306:Risk; D013548:Sweden; D055815:Young Adult
chemical_list: D007166:Immunosuppressive Agents
keywords: autoimmune disease; diagnosis; immune thrombocytopenia; infection; treatment