title: Cluster lot quality assurance sampling: effect of increasing the number of clusters on classification precision and operational feasibility.
abstract: BACKGROUND
  To assess the quality of supplementary immunization activities (SIAs), the Global Polio Eradication Initiative (GPEI) has used cluster lot quality assurance sampling (C-LQAS) methods since 2009. However, since the inception of C-LQAS, questions have been raised about the optimal balance between operational feasibility and precision of classification of lots to identify areas with low SIA quality that require corrective programmatic action.
  
  
  METHODS
  To determine if an increased precision in classification would result in differential programmatic decision making, we conducted a pilot evaluation in 4 local government areas (LGAs) in Nigeria with an expanded LQAS sample size of 16 clusters (instead of the standard 6 clusters) of 10 subjects each.
  
  
  RESULTS
  The results showed greater heterogeneity between clusters than the assumed standard deviation of 10%, ranging from 12% to 23%. Comparing the distribution of 4-outcome classifications obtained from all possible combinations of 6-cluster subsamples to the observed classification of the 16-cluster sample, we obtained an exact match in classification in 56% to 85% of instances.
  
  
  CONCLUSIONS
  We concluded that the 6-cluster C-LQAS provides acceptable classification precision for programmatic action. Considering the greater resources required to implement an expanded C-LQAS, the improvement in precision was deemed insufficient to warrant the effort.
authors.affiliation: Research, Policy and Product Development, Global Polio Eradication Department, World Health Organization, Geneva, Switzerland.
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Okayasu
authors.affiliation: Research, Policy and Product Development, Global Polio Eradication Department, World Health Organization, Geneva, Switzerland.
authors.forename: Alexandra E
authors.initials: AE
authors.lastname: Brown
authors.affiliation: Country Office, World Health Organization, Abuja, Nigeria.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Nzioki
authors.affiliation: Country Office, World Health Organization, Abuja, Nigeria.
authors.forename: Alex N
authors.initials: AN
authors.lastname: Gasasira
authors.affiliation: Research, Policy and Product Development, Global Polio Eradication Department, World Health Organization, Geneva, Switzerland.
authors.forename: Marina
authors.initials: M
authors.lastname: Takane
authors.affiliation: Country Office, World Health Organization, Abuja, Nigeria.
authors.forename: Pascal
authors.initials: P
authors.lastname: Mkanda
authors.affiliation: Global Immunization Division, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Steven G F
authors.initials: SG
authors.lastname: Wassilak
authors.affiliation: Research, Policy and Product Development, Global Polio Eradication Department, World Health Organization, Geneva, Switzerland.
authors.forename: Roland W
authors.initials: RW
authors.lastname: Sutter
mesh_terms: D002675:Child, Preschool; D005260:Female; D006302:Health Services Research; D006801:Humans; D007117:Immunization, Secondary / Q000379:methods*; D007223:Infant; D007231:Infant, Newborn; D055810:Lot Quality Assurance Sampling / Q000379:methods*; D008297:Male; D009549:Nigeria; D011051:Poliomyelitis / Q000517:prevention & control*; D023321:Poliovirus Vaccines / Q000008:administration & dosage* / Q000276:immunology*
chemical_list: D023321:Poliovirus Vaccines
keywords: Nigeria; cluster lot quality assurance sampling; polio eradication; supplementary immunization activities; survey methods