title: Multidrug resistance among new tuberculosis cases: detecting local variation through lot quality-assurance sampling.
abstract: BACKGROUND
  Current methodology for multidrug-resistant tuberculosis (MDR TB) surveys endorsed by the World Health Organization provides estimates of MDR TB prevalence among new cases at the national level. On the aggregate, local variation in the burden of MDR TB may be masked. This paper investigates the utility of applying lot quality-assurance sampling to identify geographic heterogeneity in the proportion of new cases with multidrug resistance.
  
  
  METHODS
  We simulated the performance of lot quality-assurance sampling by applying these classification-based approaches to data collected in the most recent TB drug-resistance surveys in Ukraine, Vietnam, and Tanzania. We explored 3 classification systems- two-way static, three-way static, and three-way truncated sequential sampling-at 2 sets of thresholds: low MDR TB = 2%, high MDR TB = 10%, and low MDR TB = 5%, high MDR TB = 20%.
  
  
  RESULTS
  The lot quality-assurance sampling systems identified local variability in the prevalence of multidrug resistance in both high-resistance (Ukraine) and low-resistance settings (Vietnam). In Tanzania, prevalence was uniformly low, and the lot quality-assurance sampling approach did not reveal variability. The three-way classification systems provide additional information, but sample sizes may not be obtainable in some settings. New rapid drug-sensitivity testing methods may allow truncated sequential sampling designs and early stopping within static designs, producing even greater efficiency gains.
  
  
  CONCLUSIONS
  Lot quality-assurance sampling study designs may offer an efficient approach for collecting critical information on local variability in the burden of multidrug-resistant TB. Before this methodology is adopted, programs must determine appropriate classification thresholds, the most useful classification system, and appropriate weighting if unbiased national estimates are also desired.
authors.affiliation: Department of Global Health and Social Medicine, Harvard Medical School, Boston, MA 02115, USA. bethhedt@gmail.com
authors.forename: Bethany Lynn
authors.initials: BL
authors.lastname: Hedt
authors.forename: Frank
authors.initials: F
authors.lastname: van Leth
authors.forename: Matteo
authors.initials: M
authors.lastname: Zignol
authors.forename: Frank
authors.initials: F
authors.lastname: Cobelens
authors.forename: Wayne
authors.initials: W
authors.lastname: van Gemert
authors.forename: Nguyen Viet
authors.initials: NV
authors.lastname: Nhung
authors.forename: Svitlana
authors.initials: S
authors.lastname: Lyepshina
authors.forename: Saidi
authors.initials: S
authors.lastname: Egwaga
authors.forename: Ted
authors.initials: T
authors.lastname: Cohen
mesh_terms: D000995:Antitubercular Agents / Q000627:therapeutic use*; D024901:Drug Resistance, Multiple, Bacterial; D005843:Geography; D006801:Humans; D055810:Lot Quality Assurance Sampling / Q000379:methods* / Q000592:standards; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000187:drug effects; D015995:Prevalence; D013636:Tanzania / Q000453:epidemiology; D014397:Tuberculosis, Pulmonary / Q000188:drug therapy* / Q000382:microbiology; D014455:Ukraine / Q000453:epidemiology; D014744:Vietnam / Q000453:epidemiology
chemical_list: D000995:Antitubercular Agents