title: Diagnostic Accuracy of Recombinant Immunoglobulin-like Protein A-Based IgM ELISA for the Early Diagnosis of Leptospirosis in the Philippines.
abstract: BACKGROUND
  Leptospirosis is an important but largely under-recognized public health problem in the tropics. Establishment of highly sensitive and specific laboratory diagnosis is essential to reveal the magnitude of problem and to improve treatment. This study aimed to evaluate the diagnostic accuracy of a recombinant LigA protein based IgM ELISA during outbreaks in the clinical-setting of a highly endemic country.
  
  
  RESULTS
  A prospective study was conducted from October 2011 to September 2013 at a national referral hospital for infectious diseases in Manila, Philippines. Patients who were hospitalized with clinically suspected leptospirosis were enrolled. Plasma and urine were collected on admission and/or at discharge and tested using the LigA-IgM ELISA and a whole cell-based IgM ELISA. Sensitivity and specificity of these tests were evaluated with cases diagnosed by microscopic agglutination test (MAT), culture and LAMP as the composite reference standard and blood bank donors as healthy controls: the mean+3 standard deviation optical density value of healthy controls was used as the cut-off limit (0.062 for the LigA-IgM ELISA and 0.691 for the whole cell-based IgM ELISA). Of 304 patients enrolled in the study, 270 (89.1%) were male and the median age was 30.5 years; 167 (54.9%) were laboratory confirmed. The sensitivity and ROC curve AUC for the LigA-IgM ELISA was significantly greater than the whole cell-based IgM ELISA (69.5% vs. 54.3%, p<0.01; 0.90 vs. 0.82, p<0.01) on admission, but not at discharge. The specificity of LigA-IgM ELISA and whole cell-based IgM ELISA were not significantly different (98% vs. 97%). Among 158 MAT negative patients, 53 and 28 were positive by LigA- and whole cell-based IgM ELISA, respectively; if the laboratory confirmation was re-defined by LigA-IgM ELISA and LAMP, the clinical findings were more characteristic of leptospirosis than the diagnosis based on MAT/culture/LAMP.
  
  
  CONCLUSIONS
  The newly developed LigA-IgM ELISA is more sensitive than the whole cell-based IgM based ELISA. Although the final diagnosis must be validated by more specific tests, LigA-IgM ELISA could be a useful diagnostic test in a real clinical-setting, where diagnosis is needed in the early phase of infection.
authors.affiliation: Department of Clinical Tropical Medicine, Institute of Tropical Medicine, Nagasaki University Graduate School of Biomedical Science, Sakamoto, Nagasaki, Japan.
authors.forename: Emi
authors.initials: E
authors.lastname: Kitashoji
authors.affiliation: Department of Bacteriology I, National Institute of Infectious Diseases, Toyama, Shinjuku-ku, Tokyo, Japan.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Koizumi
authors.affiliation: San Lazaro Hospital, Santa Cruz, Manila, Republic of the Philippines.
authors.forename: Talitha Lea V
authors.initials: TL
authors.lastname: Lacuesta
authors.affiliation: Department of Clinical Tropical Medicine, Institute of Tropical Medicine, Nagasaki University Graduate School of Biomedical Science, Sakamoto, Nagasaki, Japan; Department of Community Medicine, Kanazawa Medical University Himi Municipal Hospital, Himi City, Toyama, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Usuda
authors.affiliation: San Lazaro Hospital, Santa Cruz, Manila, Republic of the Philippines.
authors.forename: Maricel R
authors.initials: MR
authors.lastname: Ribo
authors.affiliation: San Lazaro Hospital, Santa Cruz, Manila, Republic of the Philippines.
authors.forename: Edith S
authors.initials: ES
authors.lastname: Tria
authors.affiliation: San Lazaro Hospital, Santa Cruz, Manila, Republic of the Philippines.
authors.forename: Winston S
authors.initials: WS
authors.lastname: Go
authors.affiliation: Department of Infectious Diseases, Nagasaki University Hospital, Sakamoto, Nagasaki, Japan.
authors.forename: Maiko
authors.initials: M
authors.lastname: Kojiro
authors.affiliation: Department of Global Health, School of Tropical Medicine and Global Health, Nagasaki University, Sakamoto, Nagasaki, Japan; Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Parry
authors.affiliation: San Lazaro Hospital, Santa Cruz, Manila, Republic of the Philippines.
authors.forename: Efren M
authors.initials: EM
authors.lastname: Dimaano
authors.affiliation: San Lazaro Hospital, Santa Cruz, Manila, Republic of the Philippines.
authors.forename: Jose B
authors.initials: JB
authors.lastname: Villarama
authors.affiliation: Department of Bacteriology I, National Institute of Infectious Diseases, Toyama, Shinjuku-ku, Tokyo, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ohnishi
authors.affiliation: Department of Clinical Tropical Medicine, Institute of Tropical Medicine, Nagasaki University Graduate School of Biomedical Science, Sakamoto, Nagasaki, Japan.
authors.forename: Motoi
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Department of Clinical Tropical Medicine, Institute of Tropical Medicine, Nagasaki University Graduate School of Biomedical Science, Sakamoto, Nagasaki, Japan.
authors.forename: Koya
authors.initials: K
authors.lastname: Ariyoshi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000907:Antibodies, Bacterial / Q000276:immunology*; D000942:Antigens, Bacterial / Q000276:immunology*; D002648:Child; D042241:Early Diagnosis; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology*; D007919:Leptospira / Q000276:immunology* / Q000302:isolation & purification; D007922:Leptospirosis / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D010679:Philippines; D011446:Prospective Studies; D011994:Recombinant Proteins; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013205:Staphylococcal Protein A / Q000276:immunology; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D007075:Immunoglobulin M; D011994:Recombinant Proteins; D013205:Staphylococcal Protein A