title: A Novel Sample Processing Method for Rapid Detection of Tuberculosis in the Stool of Pediatric Patients Using the Xpert MTB/RIF Assay.
abstract: BACKGROUND
  Tuberculosis (TB) is difficult to diagnose in children using molecular tests, because children have difficulty providing respiratory samples. Stool could replace sputum for diagnostic TB testing if adequate sample processing techniques were available.
  
  
  METHODS
  We developed a rapid method to process large volumes of stool for downstream testing by the Xpert MTB/RIF (Xpert) TB-detection assay. The method was tested and optimized on stool samples spiked with known numbers of M. tuberculosis colony forming units (CFU), and stools from M. tuberculosis-infected cynomolgus macaques (Macaca fascicularis). Performance was scored on number of positive Xpert tests, the cycle thresholds (Cts) of the Xpert sample-processing control (SPC), and the Cts of the M. tuberculosis-specific rpoB probes. The method was then validated on 20 confirmed TB cases and 20 controls in Durban, South Africa.
  
  
  RESULTS
  The assay's analytical limit of detection was 1,000 CFU/g of stool. As much as one gram of spiked stool could be tested without showing increased PCR inhibition. In analytical spiking experiments using human stool, 1g samples provided the best sensitivity compared to smaller amounts of sample. However, in Macaques with TB, 0.6g stool samples performed better than either 0.2g or 1.2g samples. Testing the stool of pediatric TB suspects and controls suggested an assay sensitivity of 85% (95% CI 0.6-0.9) and 84% (95% CI 0.6-0.96) for 0.6g and 1.2g stool samples, respectively, and a specificity of 100% (95% CI 0.77-1) and 94% (95% CI 0.7-0.99), respectively.
  
  
  CONCLUSIONS
  This novel approach may permit simple and rapid detection of TB using pediatric stool samples.
authors.affiliation: Center for Infectious Diseases, New Jersey Medical School - Rutgers University, Newark, New Jersey, United States of America.
authors.forename: Padmapriya P
authors.initials: PP
authors.lastname: Banada
authors.affiliation: KwaZulu-Natal Research Institute for TB/HIV (K-RITH), Durban, South Africa.
authors.forename: Uvistra
authors.initials: U
authors.lastname: Naidoo
authors.affiliation: Center for Infectious Diseases, New Jersey Medical School - Rutgers University, Newark, New Jersey, United States of America.
authors.forename: Srinidhi
authors.initials: S
authors.lastname: Deshpande
authors.affiliation: KwaZulu-Natal Research Institute for TB/HIV (K-RITH), Durban, South Africa.
authors.forename: Farina
authors.initials: F
authors.lastname: Karim
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: JoAnne L
authors.initials: JL
authors.lastname: Flynn
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Melanie
authors.initials: M
authors.lastname: O'Malley
authors.affiliation: Cepheid, 904 Caribbean Drive, Sunnyvale, California, United States of America.
authors.forename: Martin
authors.initials: M
authors.lastname: Jones
authors.affiliation: Cepheid, Bothell, Washington, United States of America.
authors.forename: Oliver
authors.initials: O
authors.lastname: Nanassy
authors.affiliation: KwaZulu-Natal Research Institute for TB/HIV (K-RITH), Durban, South Africa.
authors.forename: Prakash
authors.initials: P
authors.lastname: Jeena
authors.affiliation: Center for Infectious Diseases, New Jersey Medical School - Rutgers University, Newark, New Jersey, United States of America.
authors.forename: David
authors.initials: D
authors.lastname: Alland
mesh_terms: D000818:Animals; D002648:Child; D005243:Feces / Q000382:microbiology*; D006801:Humans; D008252:Macaca fascicularis; D008253:Macaca mulatta; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D012680:Sensitivity and Specificity; D013048:Specimen Handling; D014376:Tuberculosis / Q000175:diagnosis*