title: The risk and timing of tuberculosis diagnosed in smear-negative TB suspects: a 12 month cohort study in Harare, Zimbabwe.
abstract: BACKGROUND
  Cases of smear-negative TB have increased dramatically in high prevalence HIV settings and pose considerable diagnostic and management challenges.
  
  
  RESULTS
  Between February 2006 and July 2007, a cohort study nested within a cluster-randomised trial of community-based case finding strategies for TB in Harare, Zimbabwe was undertaken. Participants who had negative sputum smears and remained symptomatic of TB were follow-up for one year with standardised investigations including HIV testing, repeat sputum smears, TB culture and chest radiography. Defaulters were actively traced to the community. The objectives were to investigate the incidence and risk factors for TB. TB was diagnosed in 218 (18.2%) participants, of which 39.4% was bacteriologically confirmed. Most cases (84.2%) were diagnosed within 3 months, but TB incidence remained high thereafter (111.3 per 1000 person-years, 95% CI: 86.6 to 146.3). HIV prevalence was 63.3%, and HIV-infected individuals had a 3.5-fold higher risk of tuberculosis than HIV-negative individuals.
  
  
  CONCLUSIONS
  We found that diagnosis of TB was insensitive and slow, even with early radiography and culture. Until more sensitive and rapid diagnostic tests become widely available, a much more proactive and integrated approach towards prompt initiation of ART, ideally from within TB clinics and without waiting for TB to be excluded, is needed to minimise the risk and consequences of diagnostic delay.
authors.affiliation: Biomedical Research and Training Institute, Harare, Zimbabwe.
authors.forename: Munyaradzi
authors.initials: M
authors.lastname: Dimairo
authors.forename: Peter
authors.initials: P
authors.lastname: MacPherson
authors.forename: Tsitsi
authors.initials: T
authors.lastname: Bandason
authors.forename: Abbas
authors.initials: A
authors.lastname: Zezai
authors.forename: Shungu S
authors.initials: SS
authors.lastname: Munyati
authors.forename: Anthony E
authors.initials: AE
authors.lastname: Butterworth
authors.forename: Stanley
authors.initials: S
authors.lastname: Mungofa
authors.forename: Simba
authors.initials: S
authors.lastname: Rusikaniko
authors.forename: Katherine
authors.initials: K
authors.lastname: Fielding
authors.forename: Peter R
authors.initials: PR
authors.lastname: Mason
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Corbett
mesh_terms: D015331:Cohort Studies; D015658:HIV Infections / Q000150:complications / Q000453:epidemiology; D013183:Sputum / Q000382:microbiology; D013997:Time Factors; D014376:Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology; D015030:Zimbabwe