title: Clinical utility of a commercial LAM-ELISA assay for TB diagnosis in HIV-infected patients using urine and sputum samples.
abstract: BACKGROUND
  The accurate diagnosis of TB in HIV-infected patients, particularly with advanced immunosuppression, is difficult. Recent studies indicate that a lipoarabinomannan (LAM) assay (Clearview-TB(R)-ELISA) may have some utility for the diagnosis of TB in HIV-infected patients; however, the precise subgroup that may benefit from this technology requires clarification. The utility of LAM in sputum samples has, hitherto, not been evaluated.
  
  
  METHODS
  LAM was measured in sputum and urine samples obtained from 500 consecutively recruited ambulant patients, with suspected TB, from 2 primary care clinics in South Africa. Culture positivity for M. tuberculosis was used as the reference standard for TB diagnosis.
  
  
  RESULTS
  Of 440 evaluable patients 120/387 (31%) were HIV-infected. Urine-LAM positivity was associated with HIV positivity (p = 0.007) and test sensitivity, although low, was significantly higher in HIV-infected compared to uninfected patients (21% versus 6%; p<0.001), and also in HIV-infected participants with a CD4 <200 versus >200 cells/mm(3) (37% versus 0%; p = 0.003). Urine-LAM remained highly specific in all 3 subgroups (95%-100%). 25% of smear-negative but culture-positive HIV-infected patients with a CD4 <200 cells/mm(3) were positive for urine-LAM. Sputum-LAM had good sensitivity (86%) but poor specificity (15%) likely due to test cross-reactivity with several mouth-residing organisms including actinomycetes and nocardia species.
  
  
  CONCLUSIONS
  These preliminary data indicate that in a high burden primary care setting the diagnostic usefulness of urine-LAM is limited, as a rule-in test, to a specific patient subgroup i.e. smear-negative HIV-infected TB patients with a CD4 count <200 cells/mm(3), who would otherwise have required further investigation. However, even in this group sensitivity was modest. Future and adequately powered studies in a primary care setting should now specifically target patients with suspected TB who have advanced HIV infection.
authors.affiliation: Lung Infection and Immunity Unit, Department of Medicine, Division of Pulmonology and Clinical Immunology, UCT Lung Institute, University of Cape Town, Cape Town, South Africa. keertan.dheda@uct.ac.za
authors.forename: Keertan
authors.initials: K
authors.lastname: Dheda
authors.forename: Virginia
authors.initials: V
authors.lastname: Davids
authors.forename: Laura
authors.initials: L
authors.lastname: Lenders
authors.forename: Teri
authors.initials: T
authors.lastname: Roberts
authors.forename: Richard
authors.initials: R
authors.lastname: Meldau
authors.forename: Daphne
authors.initials: D
authors.lastname: Ling
authors.forename: Laurence
authors.initials: L
authors.lastname: Brunet
authors.forename: Richard
authors.initials: R
authors.lastname: van Zyl Smit
authors.forename: Jonathan
authors.initials: J
authors.lastname: Peter
authors.forename: Clare
authors.initials: C
authors.lastname: Green
authors.forename: Motasim
authors.initials: M
authors.lastname: Badri
authors.forename: Leonardo
authors.initials: L
authors.lastname: Sechi
authors.forename: Surendra
authors.initials: S
authors.lastname: Sharma
authors.forename: Michael
authors.initials: M
authors.lastname: Hoelscher
authors.forename: Rodney
authors.initials: R
authors.lastname: Dawson
authors.forename: Andrew
authors.initials: A
authors.lastname: Whitelaw
authors.forename: Jonathan
authors.initials: J
authors.lastname: Blackburn
authors.forename: Madhukar
authors.initials: M
authors.lastname: Pai
authors.forename: Alimuddin
authors.initials: A
authors.lastname: Zumla
mesh_terms: D000328:Adult; D000465:Algorithms; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D015658:HIV Infections / Q000150:complications* / Q000378:metabolism / Q000652:urine / Q000821:virology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000378:metabolism; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013183:Sputum / Q000378:metabolism; D016896:Treatment Outcome; D014376:Tuberculosis / Q000150:complications* / Q000175:diagnosis* / Q000276:immunology* / Q000378:metabolism / Q000652:urine; D016482:Urinalysis