title: Urine lipoarabinomannan point-of-care testing in patients affected by pulmonary nontuberculous mycobacteria--experiences from the Danish Cystic Fibrosis cohort study.
abstract: BACKGROUND
  The urine lipoarabinomannan (LAM) strip test has been suggested as a new point-of-care test for active tuberculosis (TB) among human immunodeficiency virus (HIV) infected individuals. It has been questioned if infections with nontuberculous mycobacteria (NTM) affect assay specificity. We set forth to investigate if the test detects LAM in urine from a Danish cystic fibrosis (CF) population characterized by a high NTM prevalence and negligible TB exposure.
  
  
  METHODS
  Patients followed at the Copenhagen CF Center were comprehensively screened for pulmonary NTM infection between May 2012 and December 2013. Urine samples were tested for LAM using the 2013 Determine™ TB LAM Ag strip test.
  
  
  RESULTS
  Three-hundred and six patients had a total of 3,322 respiratory samples cultured for NTM and 198 had urine collected (65%). A total of 23/198 (12%) had active pulmonary NTM infection. None had active TB. The TB-LAM test had an overall positive rate of 2.5% applying a grade 2 cut-point as positivity threshold, increasing to 10.6% (21/198) if a grade 1 cut-point was applied. Among patients with NTM infection 2/23 (8.7%) had a positive LAM test result at the grade 2 cut-point and 9/23 (39.1%) at the grade 1 cut -point. Test specificity for NTM diagnosis was 98.3% and 93.1 for grade 2 and 1 cut-point respectively.
  
  
  CONCLUSIONS
  This is the first study to assess urine LAM detection in patients with confirmed NTM infection. The study demonstrated low cross-reactivity due to NTM infection when using the recommended grade 2 cut-point as positivity threshold. This is reassuring in regards to interpretation of the LAM test for TB diagnosis in a TB prevalent setting. The test was not found suitable for NTM detection among patients with CF.
authors.affiliation: Department of Infectious Diseases, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark. tavs.qvist@gmail.com.
authors.forename: Tavs
authors.initials: T
authors.lastname: Qvist
authors.affiliation: Department of Infectious Diseases, Odense University Hospital, Odense, Denmark. isik@dadlnet.dk.
authors.forename: Isik S
authors.initials: IS
authors.lastname: Johansen
authors.affiliation: Department of Infectious Diseases, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark. tania.pressler@gmail.com.
authors.forename: Tania
authors.initials: T
authors.lastname: Pressler
authors.affiliation: Department of Clinical Microbiology, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark. hoiby@dadlnet.dk.
authors.forename: Niels
authors.initials: N
authors.lastname: Høiby
authors.affiliation: Department of Infectious Diseases, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark. bengaard@dadlnet.dk.
authors.forename: Aase B
authors.initials: AB
authors.lastname: Andersen
authors.affiliation: Department of Infectious Diseases, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark. terese.katzenstein@regionh.dk.
authors.forename: Terese L
authors.initials: TL
authors.lastname: Katzenstein
authors.affiliation: Department of Infectious Diseases, Odense University Hospital, Odense, Denmark. steph@medicinsk.dk.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Bjerrum
mesh_terms: D000328:Adult; D000942:Antigens, Bacterial / Q000652:urine*; D015415:Biomarkers / Q000652:urine; D015331:Cohort Studies; D003429:Cross Reactions; D003550:Cystic Fibrosis / Q000150:complications*; D003718:Denmark; D005260:Female; D006801:Humans; D008070:Lipopolysaccharides / Q000652:urine*; D008297:Male; D009165:Mycobacterium Infections, Nontuberculous / Q000175:diagnosis* / Q000209:etiology / Q000652:urine; D009170:Nontuberculous Mycobacteria / Q000276:immunology*; D019095:Point-of-Care Systems; D011446:Prospective Studies; D012680:Sensitivity and Specificity
chemical_list: D000942:Antigens, Bacterial; D015415:Biomarkers; D008070:Lipopolysaccharides; C050016:lipoarabinomannan