title: Serum levels of immunoglobulins and severity of community-acquired pneumonia.
abstract: BACKGROUND
  There is evidence of a relationship between severity of infection and inflammatory response of the immune system. The objective is to assess serum levels of immunoglobulins and to establish its relationship with severity of community-acquired pneumonia (CAP) and clinical outcome.
  
  
  METHODS
  This was an observational and cross-sectional study in which 3 groups of patients diagnosed with CAP were compared: patients treated in the outpatient setting (n=54), patients requiring in-patient care (hospital ward) (n=173), and patients requiring admission to the intensive care unit (ICU) (n=191).
  
  
  RESULTS
  Serum total IgG (and IgG subclasses IgG1, IgG2, IgG3, IgG4), IgA and IgM were measured at the first clinical visit. Normal cutpoints were defined as the lowest value obtained in controls (≤680, ≤323, ≤154, ≤10, ≤5, ≤30 and ≤50 mg/dL for total IgG, IgG1, IgG2, IgG3, IgG4, IgM and IgA, respectively). Serum immunoglobulin levels decreased in relation to severity of CAP. Low serum levels of total IgG, IgG1 and IgG2 showed a relationship with ICU admission. Low serum level of total IgG was independently associated with ICU admission (OR=2.45, 95% CI 1.4 to 4.2, p=0.002), adjusted by the CURB-65 severity score and comorbidities (chronic respiratory and heart diseases). Low levels of total IgG, IgG1 and IgG2 were significantly associated with 30-day mortality.
  
  
  CONCLUSIONS
  Patients with severe CAP admitted to the ICU showed lower levels of immunoglobulins than non-ICU patients and this increased mortality.
authors.affiliation: Critical Care Unit , Hospital de Mataró, Universitat Autònoma de Barcelona, Ciber Enfermedades Respiratorias, CIBERES , Barcelona , Spain.
authors.forename: Mari C
authors.initials: MC
authors.lastname: de la Torre
authors.affiliation: Unitat Suport Recerca Metropolitana Nord ICS, Santa Coloma de Gramanet , Barcelona , Spain.
authors.forename: Pere
authors.initials: P
authors.lastname: Torán
authors.affiliation: Research Unit , Hospital de Mataró, CIBEREHD , Barcelona , Spain.
authors.forename: Mateu
authors.initials: M
authors.lastname: Serra-Prat
authors.affiliation: Research Unit , Hospital de Mataró, CIBEREHD , Barcelona , Spain.
authors.forename: Elisabet
authors.initials: E
authors.lastname: Palomera
authors.affiliation: Department of Biochemistry , Hospital de Mataró, Universitat Autònoma de Barcelona, Mataró , Barcelona , Spain.
authors.forename: Estel
authors.initials: E
authors.lastname: Güell
authors.affiliation: Department of Biochemistry , Hospital de Mataró, Universitat Autònoma de Barcelona, Mataró , Barcelona , Spain.
authors.forename: Ester
authors.initials: E
authors.lastname: Vendrell
authors.affiliation: Department of Biochemistry , Hospital de Mataró, Universitat Autònoma de Barcelona, Mataró , Barcelona , Spain.
authors.forename: Joan Carles
authors.initials: JC
authors.lastname: Yébenes
authors.affiliation: Service of Pneumology , Institut Clínic del Torax, IDIBAPS, Hospital Clínic de Barcelona, Universitat de Barcelona, CIBERES , Barcelona , Spain.
authors.forename: Antoni
authors.initials: A
authors.lastname: Torres
authors.affiliation: Department of Biochemistry , Hospital de Mataró, Universitat Autònoma de Barcelona, Mataró , Barcelona , Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Almirall
keywords: Immunodeficiency; Pneumonia; Respiratory Infection