title: Diagnostic accuracy of a urine lipoarabinomannan strip-test for TB detection in HIV-infected hospitalised patients.
abstract: Lack of point-of-care tests for tuberculosis (TB) result in diagnostic delay, and increased mortality and healthcare-related costs. The urine Determine(TM) TB-LAM point-of-care strip-test was evaluated in 335 prospectively-recruited hospitalised patients with suspected TB-HIV co-infection (group 1) and from 88 HIV-infected hospitalised patients with non-TB diagnoses (group 2). Cut-off point-specific analyses were performed using: 1) a microbiological reference standard (culture positive versus negative); and 2) a composite reference standard (exclusion of patients with clinical-TB from the culture-negative group). Using the microbiological reference and the manufacturer-recommended grade-1 cut-off point, LAM sensitivity and specificity was 66% (95% CI 57-74%). By contrast, using the composite reference sensitivity was 60% (95% CI 53-67%) and specificity improved to 96% (95% CI 89-100%) (p=0.001). The same pattern was seen when the grade-2 cut-off point was used (specificity 75% versus 96%; p=0.01). In group two patients specificity was poor using the grade-1 cut-off point, but improved significantly when the grade-2 cut-off point was used (90% versus 99%; p=0.009). The grade-2 cut-off point also offered superior inter-reader reliability (p=0.002). Sensitivity was highest in those with a CD4 <200 cells per mL. LAM combined with smear-microscopy was able to rule-in TB in 71% of Mycobacterium tuberculosis culture-positive patients. This preliminary study indicates that the LAM strip-test may be a potentially useful rapid rule-in test for TB in hospitalised patients with advanced immunosuppression. The grade 2, but not the manufacturer-recommended grade 1 cut-off point, offered superior rule-in utility and inter-reader reliability. Larger studies to evaluate cut-off points and diagnostic accuracy are urgently required.
authors.affiliation: Division of Pulmonology & UCT Lung Institute, Dept of Medicine, University of Cape Town, Cape Town, South Africa.
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Peter
authors.forename: Grant
authors.initials: G
authors.lastname: Theron
authors.forename: Richard
authors.initials: R
authors.lastname: van Zyl-Smit
authors.forename: Asheen
authors.initials: A
authors.lastname: Haripersad
authors.forename: Lynelle
authors.initials: L
authors.lastname: Mottay
authors.forename: Sarah
authors.initials: S
authors.lastname: Kraus
authors.forename: Anke
authors.initials: A
authors.lastname: Binder
authors.forename: Richard
authors.initials: R
authors.lastname: Meldau
authors.forename: Anneli
authors.initials: A
authors.lastname: Hardy
authors.forename: Keertan
authors.initials: K
authors.lastname: Dheda
mesh_terms: D000328:Adult; D005260:Female; D015658:HIV Infections / Q000150:complications; D006760:Hospitalization; D006801:Humans; D008070:Lipopolysaccharides / Q000652:urine*; D008297:Male; D011446:Prospective Studies; D011934:Reagent Strips; D015203:Reproducibility of Results; D014376:Tuberculosis / Q000150:complications / Q000175:diagnosis* / Q000652:urine*
chemical_list: D008070:Lipopolysaccharides; D011934:Reagent Strips; C050016:lipoarabinomannan