title: Nonspecificity of assaying for IgG antibody to pneumolysin in circulating immune complexes as a means to diagnose pneumococcal pneumonia.
abstract: Detection of immunoglobulin G (IgG) antibody to pneumolysin (PLY) in precipitated circulating immune complexes (CICs) has been used to diagnose pneumococcal pneumonia. With care to include appropriate controls, we precipitated and dissociated CICs and then assayed for IgG antibody to PLY. We detected IgG antibody to PLY in CICs that were precipitated from serum samples that were obtained at the time of admission to the hospital from 5 (23%) of 22 healthy adults, 7 (44%) of 16 subjects with stable chronic obstructive pulmonary disease, 10 (63%) of 16 subjects colonized with Streptococcus pneumoniae, and 9 (60%) of 15 patients with nonbacteremic pneumococcal pneumonia. Of the 16 patients with bacteremic pneumococcal pneumonia, 4 (25%) had IgG antibody to PLY at the time of admission, and 8 (50%) had IgG antibody to PLY in convalescence. Levels of IgG antibody in CICs closely correlated with serum levels of IgG antibody to PLY, implicating precipitation of free serum antibody in tests with false-positive results. Detection of IgG antibody to PLY in precipitated CICs is not a reliable method for diagnosing pneumococcal pneumonia.
authors.affiliation: Medical Service, Infectious Disease Section, Houston Veterans Affairs Medical Center, Houston, TX 77030, USA. daniel.musher@med.va.gov
authors.forename: D M
authors.initials: DM
authors.lastname: Musher
authors.forename: R
authors.initials: R
authors.lastname: Mediwala
authors.forename: H M
authors.initials: HM
authors.lastname: Phan
authors.forename: G
authors.initials: G
authors.lastname: Chen
authors.forename: R E
authors.initials: RE
authors.lastname: Baughn
mesh_terms: D000328:Adult; D000918:Antibody Specificity; D000936:Antigen-Antibody Complex / Q000097:blood* / Q000737:chemistry / Q000276:immunology; D001426:Bacterial Proteins; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000276:immunology; D008875:Middle Aged; D011018:Pneumonia, Pneumococcal / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D013296:Streptococcus pneumoniae / Q000276:immunology; D013301:Streptolysins / Q000276:immunology*
chemical_list: D000936:Antigen-Antibody Complex; D001426:Bacterial Proteins; D007074:Immunoglobulin G; D013301:Streptolysins; C032290:plY protein, Streptococcus pneumoniae