title: In-house ELISA screening using a locally-isolated Leptospira in Malaysia: determination of its cut-off points.
abstract: BACKGROUND
  Leptospirosis is a zoonotic disease caused by Leptospira species and is distributed globally. Microscopic agglutination test (MAT) is the serological 'gold standard' for diagnosis of leptospirosis but it is time-consuming and labour-intensive. An alternative serological method that is rapid, sensitive and specific is important for early treatment to reduce morbidity and mortality. The use of local Leptospira isolation may improve the sensitivity and specificity of the test because it may varies from one geographical region to another region. The objective of this study was to determine the sensitivity, specificity and cut-off points for an in-house Immunoglobulin M (IgM) enzyme-linked immunosorbent assay (ELISA) using a locally isolated Leptospiral strain IMR/175 as the antigen for the detection of anti-Leptospiral IgM.
  
  
  METHODS
  Serum samples from 270 patients with clinical symptoms of leptospirosis were subjected to the in-house IgM ELISA, MAT and Leptospirosis rapid test. The optimal cut-off values for positivity and negativity of the IgM ELISA were determined by Receiver Operating Characteristic curves and mean ± 2 standard deviation (SD) analyses of the ELISA values.
  
  
  RESULTS
  The area under the curve (AUC) which indicates the diagnostic performance of the in-house IgM ELISA was 0.953 (95% Confidence Interval, CI: 0.928, 0.978). The sensitivity and specificity of 90.38% and 87.72% respectively were obtained with the cut-off point of 0.55. A higher sensitivity (96.15%) was obtained when the cut-off point was set at 0.45.
  
  
  CONCLUSIONS
  The in-house IgM ELISA assay using local Leptospira isolation was shown to be sensitive and may be suitable to use for the serological diagnosis of leptospirosis for our local hospital setting.
authors.forename: Xue Ting
authors.initials: XT
authors.lastname: Tan
authors.forename: Fairuz
authors.initials: F
authors.lastname: Amran
authors.forename: Kee
authors.initials: K
authors.lastname: Chee Cheong
authors.forename: Norazah
authors.initials: N
authors.lastname: Ahmad
mesh_terms: D000372:Agglutination Tests; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D019540:Area Under Curve; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood; D007919:Leptospira / Q000302:isolation & purification; D007922:Leptospirosis / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D008296:Malaysia; D012372:ROC Curve; D015047:Zoonoses
chemical_list: D000907:Antibodies, Bacterial; D007075:Immunoglobulin M