title: Duration of cough, TB suspects' characteristics and service factors determine the yield of smear microscopy.
abstract: OBJECTIVE
  To determine the efficiency of routine tuberculosis (TB) case detection by examining sputum smear positivity for acid-fast bacilli in relation to duration of cough, characteristics of TB suspects examined and health service factors.
  
  
  METHODS
  We combined patient interviews with routine data from laboratory registers in 6 health care facilities in San Juan de Lurigancho district, Lima, Peru. A TB case was defined as a TB suspect with at least one positive sputum smear. We calculated adjusted odds ratios with 95% confidence intervals for the association between smear positivity and health service and patient's characteristics.
  
  
  RESULTS
  Smear positivity was 7.3% (321/4376). Of the 4376 adults submitting sputa, 55.3% (2418) reported cough for <14 days. In this group, smear microscopy yielded 3.2% (78/2418) positive results vs. 12.4% (243/1958) in patients coughing for 14 or more days. Having cough for >2 weeks, being referred by health care staff, attending a secondary-level health care facility, male sex and age between 15 and 44 years were independent determinants of smear positivity.
  
  
  CONCLUSIONS
  Routine case detection yields a low proportion of smear-positive cases because of the inclusion of a high proportion of patients without cough or coughing for <2 weeks. Adherence to the national TB control programme guidelines on the selection of TB suspects would have a positive impact on the smear positivity rate, reduce laboratory costs and workload and possibly improve the reading quality of smear microscopy.
authors.affiliation: Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru. larissaotero@gmail.com
authors.forename: L
authors.initials: L
authors.lastname: Otero
authors.forename: R
authors.initials: R
authors.lastname: Ugaz
authors.forename: G
authors.initials: G
authors.lastname: Dieltiens
authors.forename: E
authors.initials: E
authors.lastname: González
authors.forename: K
authors.initials: K
authors.lastname: Verdonck
authors.forename: C
authors.initials: C
authors.lastname: Seas
authors.forename: A
authors.initials: A
authors.lastname: Van Deun
authors.forename: E
authors.initials: E
authors.lastname: Gotuzzo
authors.forename: P
authors.initials: P
authors.lastname: Van der Stuyft
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D003371:Cough / Q000382:microbiology*; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D010568:Peru / Q000453:epidemiology; D017678:Sex Distribution; D013183:Sputum / Q000382:microbiology*; D013997:Time Factors; D014397:Tuberculosis, Pulmonary / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D055815:Young Adult