title: Enzyme-linked immunoassay for dengue virus IgM and IgG antibodies in serum and filter paper blood.
abstract: BACKGROUND
  The reproducibilty of dengue IgM and IgG ELISA was studied in serum and filter paper blood spots from Vietnamese febrile patients.
  
  
  METHODS
  781 pairs of acute (t0) and convalescent sera, obtained after three weeks (t3) and 161 corresponding pairs of filter paper blood spots were tested with ELISA for dengue IgG and IgM. 74 serum pairs were tested again in another laboratory with similar methods, after a mean of 252 days.
  
  
  RESULTS
  Cases were classified as no dengue (10 %), past dengue (55%) acute primary (7%) or secondary (28%) dengue. Significant differences between the two laboratories' results were found leading to different diagnostic classification (kappa 0.46, p < 0.001). Filter paper results correlated poorly to serum values, being more variable and lower with a mean (95% CI) difference of 0.82 (0.36 to 1.28) for IgMt3, 0.94 (0.51 to 1.37) for IgGt0 and 0.26 (-0.20 to 0.71) for IgGt3. This also led to differences in diagnostic classification (kappa value 0.44, p < 0.001) The duration of storage of frozen serum and dried filter papers, sealed in nylon bags in an air-conditioned room, had no significant effect on the ELISA results.
  
  
  CONCLUSIONS
  Dengue virus IgG antibodies in serum and filter papers was not affected by duration of storage, but was subject to inter-laboratory variability. Dengue virus IgM antibodies measured in serum reconstituted from blood spots on filter papers were lower than in serum, in particular in the acute phase of disease. Therefore this method limits its value for diagnostic confirmation of individual patients with dengue virus infections. However the detection of dengue virus IgG antibodies eluted from filter paper can be used for sero-prevalence cross sectional studies.
authors.affiliation: Division of Infectious Diseases, Tropical Medicine and AIDS, Academic Medical Center, PO Box 22700, 1100 DE Amsterdam, The Netherlands. ngatran_crh@yahoo.com
authors.forename: Thanh Nga T
authors.initials: TN
authors.lastname: Tran
authors.forename: Peter J
authors.initials: PJ
authors.lastname: de Vries
authors.forename: Lan Phuong
authors.initials: LP
authors.lastname: Hoang
authors.forename: Giao T
authors.initials: GT
authors.lastname: Phan
authors.forename: Hung Q
authors.initials: HQ
authors.lastname: Le
authors.forename: Binh Q
authors.initials: BQ
authors.lastname: Tran
authors.forename: Chi Mai T
authors.initials: CM
authors.lastname: Vo
authors.forename: Nam V
authors.initials: NV
authors.lastname: Nguyen
authors.forename: Piet A
authors.initials: PA
authors.lastname: Kager
authors.forename: Nico
authors.initials: N
authors.lastname: Nagelkerke
authors.forename: Jan
authors.initials: J
authors.lastname: Groen
mesh_terms: D000914:Antibodies, Viral / Q000097:blood*; D003715:Dengue / Q000175:diagnosis* / Q000276:immunology*; D003716:Dengue Virus / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007075:Immunoglobulin M / Q000097:blood*; D008851:Micropore Filters; D010209:Paper; D015203:Reproducibility of Results; D014744:Vietnam
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G; D007075:Immunoglobulin M