title: Development of a quantitative rapid diagnostic test for multibacillary leprosy using smart phone technology.
abstract: BACKGROUND
  Despite efforts to eliminate leprosy as public health problem, delayed diagnosis and disabilities still occur in many countries. Leprosy diagnosis remains based on clinical manifestations and the number of clinicians with expertise in leprosy diagnosis is in decline. We have developed a new immunochromatographic test with the goal of producing a simple and rapid system that can be used, with a minimal amount of training, to provide an objective and consistent diagnosis of multibacillary leprosy.
  
  
  METHODS
  The test immobilizes two antigens that have been recognized as excellent candidates for serologic diagnosis (the PGL-I mimetic, ND-O, and LID-1), on a nitrocellulose membrane. This allows the detection of specific IgM and IgG antibodies within 20 minutes of the addition of patient sera. Furthermore, we coupled the NDO-LID® rapid tests with a new cell phone-based test reader platform (Smart Reader®) to provide objective interpretation that was both quantifiable and consistent.
  
  
  RESULTS
  Direct comparison of serologic responses indicated that the rapid test detected a greater proportion of leprosy patients than a lab-based PGL-I ELISA. While positive responses were detected by PGL-I ELISA in 83.3% of multibacillary patients and 15.4% of paucibacillary patients, these numbers were increased to 87% and 21.2%, respectively, when a combination of the NDO-LID® test and Smart Reader® was used. Among multibacillary leprosy the sensitivity of NDO-LID® test assessed by Smart Reader® was 87% (95% CI, 79.2-92.7%) and the specificity was 96.1% (95% CI, 91.7- 98.6%). The positive predictive value and the negative predictive value of NDO-LID® tests were 94% (95% CI, 87.4-97.8%) and 91.4% (95% CI, 85.9-95.2%), respectively.
  
  
  CONCLUSIONS
  The widespread provision of rapid diagnostic tests to facilitate the diagnosis or prognosis of multibacillary leprosy could impact on leprosy control programs by aiding early detection, directing appropriate treatment and potentially interrupting Mycobacterium leprae transmission.
authors.forename: Ludimila
authors.initials: L
authors.lastname: Paula Vaz Cardoso
authors.forename: Ronaldo Ferreira
authors.initials: RF
authors.lastname: Dias
authors.forename: Aline Araújo
authors.initials: AA
authors.lastname: Freitas
authors.forename: Emerith Mayra
authors.initials: EM
authors.lastname: Hungria
authors.forename: Regiane Morillas
authors.initials: RM
authors.lastname: Oliveira
authors.forename: Marco
authors.initials: M
authors.lastname: Collovati
authors.forename: Steven G
authors.initials: SG
authors.lastname: Reed
authors.forename: Malcolm S
authors.initials: MS
authors.lastname: Duthie
authors.affiliation: Tropical Pathology and Public Health Institute, Federal University of Goiás, 235th Street, Setor Universitário, 74605-050 Goiânia-Goiás, Brazil. mariane.stefani@pq.cnpq.br.
authors.forename: Mariane
authors.initials: M
authors.lastname: Martins Araújo Stefani
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology; D000942:Antigens, Bacterial / Q000737:chemistry / Q000276:immunology; D001431:Bacteriological Techniques / Q000379:methods*; D040421:Cell Phone; D002846:Chromatography, Affinity / Q000379:methods*; D005260:Female; D006801:Humans; D056006:Leprosy, Multibacillary / Q000175:diagnosis* / Q000276:immunology / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D009166:Mycobacterium leprae / Q000276:immunology / Q000302:isolation & purification; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial