title: Detection of Tuberculosis in HIV Co-infected Individuals: Use of Multiple ELISA Responses to 38kDa, Lipoarabinomannan and ESAT- 6 of M. tuberculosis.
abstract: BACKGROUND
  There is a constant search for more sensitive and specific laboratory markers for tuberculosis (TB) infection. The early detection of TB in HIV co infected individuals is a diagnostic challenge. This is further compounded in those harbouring extrapulmonary disease.
  
  
  OBJECTIVE
  To evaluate the use of multiple Enzyme Linked Immunosorbent Assays (ELISA) quantifying antibody responses to 38kDa, LAM and ESAT-6 M.tb antigens in detection of TB in patients with TB and HIV-TB co-infection.
  
  
  METHODS
  This is a cross-sectional study carried out in Hyderabad, India. Patient groups included 124 HIV-TB {62 with pulmonary TB (PTB) and 62 with extrapulmonary TB (ETB)}, 39 TB, 56 HIV and 57 healthy subjects (HS). A combination of anti 38kDa and LAM ELISAs measuring IgG, IgM and IgA levels and another ELISA measuring anti ESAT-6 combined antibody levels of IgG, IgM and IgA were evaluated. One-way ANOVA was performed to compare antibody responses among groups. To assess the efficacy of multiple ELISAs in detecting TB, concomitant seropositivity of an individual for all four ELISAs were evaluated for sensitivity and specificity.
  
  
  RESULTS
  A single ELISA carried out to detect TB in HIV patients showed a sensitivity ranging from 39% to 72%. The sensitivities of concomitant evaluation of multiple ELISAs were 92% for any single, 72% for any two, 44% for any three and 14% for any four. Based on the specificities, a simple algorithm for TB detection can be deduced. When four ELISAs are positive (specificity 100%) in a patient-confirmed TB; when three ELISAs are positive (specificity 98%) - probably TB; when two ELISAs are positive (specificity 95%) - possibly TB; and when one ELISA is positive (specificity 70%) - suspicion of TB.
  
  
  CONCLUSIONS
  The present study establishes the value of combining two or more M.tb antigen based ELISAs to enhance the sensitivity and specificity of TB detection in patients with tuberculosis as well as in those co-infected with HIV.
authors.affiliation: Research Scholar, Nirekshana-CODEWEL & Centre for Biotechnology, Acharya Nagarjuna University , Nagarjuna Nagar, Guntur, Andhra Pradesh, India .
authors.forename: Ravi
authors.initials: R
authors.lastname: Gutlapalli
authors.affiliation: Research Scholar, Nirekshana-CODEWEL & Centre for Biotechnology, Acharya Nagarjuna University , Nagarjuna Nagar, Guntur, Andhra Pradesh, India .
authors.forename: Aparna
authors.initials: A
authors.lastname: Sykam
authors.affiliation: Research Scholar, Nirekshana-CODEWEL & Centre for Biotechnology, Acharya Nagarjuna University , Nagarjuna Nagar, Guntur, Andhra Pradesh, India .
authors.forename: Sandeep P
authors.initials: SP
authors.lastname: Tenali
authors.affiliation: Professor and Head, Department of Biochemistry, Nizam's Institute of Medical Sciences , Punjagutta, Hyderabad, Telangana, India .
authors.forename: Priscilla
authors.initials: P
authors.lastname: Chandran
authors.affiliation: Director, CODEWEL-Nireekshana-ACET (AIDS Care Education and Training) , Hyderabad, Telangana, India .
authors.forename: Sujai
authors.initials: S
authors.lastname: Suneetha
authors.affiliation: Research Director, CODEWEL-Nireekshana-ACET (AIDS Care Education and Training) , Hyderabad, Telangana, India .
authors.forename: Lavanya M
authors.initials: LM
authors.lastname: Suneetha
keywords: Extrapulmonary TB; HIV-TB diagnosis; Pulmonary TB; TB test sensitivity