LQAS: Pitfalls, Controvery & Addressing Concerns_Luna, Nitkin, Yaggy_5.10.11

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  • 1. LQAS: Pitfalls, Controversies, and Addressing Concerns
    CORE Spring Meeting
    Jennifer Luna; Todd Nitkin; Bill Yaggy
    May 10, 2011
  • 2. LQAS is useful
    However, common mistakes can lead to problems including:
    Not collecting adequate information
    Incorrectly interpreting findings
    Improperly describing actions taken as a result of findings
  • 3. LQAS session
    Purpose: Discuss common mistakes and practical ways to avoid them
    Agenda:
    Overview of LQAS, resources and discussion of current controversies
    Experience, advice from AMREF
    Practical advice from MTI
    Small group work
    Brief plenary on results of small group work
  • 4. LQAS
    Origin in quality control for industry
    light bulbs
    Promoted for use in small population based health surveys
    Useful for monitoring because it provides information used to identify sub-divisions (supervision areas) of project area that are sub-standard
    More attention can be given to these areas.
    Does not provide coverage levels for supervision areas
  • 5. Steps
    Divide project area into supervision areas (SAs)
    Decide on level below which a supervision area is identified as priority for special attention; e.g. <85%
    Randomly select sample of 19 per SA
    Use a decision rule table to determine what number of correct responses is the cut-off for identifying SAs that need priority attention
    <20%, <1 correct response out of 19
    <50%, <7 correct responses out of 19
    85%, <14 correct responses out of 19
  • 6. Steps
    Indicators must be dichotomous (yes/no)
    Was child exclusively breastfed?
    Not for how many months was the child exclusively breastfed?
  • 7. Supervision Area (SA)
    “Lots” that you divide project area into
    Should have meaning:
    i.e. health facility catchment areas, sub-districts or other MOH administrative areas
    A
    B
    E
    D
    C
  • 8.
  • 9. Parallel Sampling
    Conducting multiple surveys at the same time using the same logistic system
    Necessary for surveys that collect information on indicators with different age groups as denominators:
    i.e. IYCF (denominator children 6-23 months);
    use of ORS for diarrhea treatment (denominator children 0-23 months with diarrhea in the last two weeks)
    Parallel sampling ensures that:
    Each indicator will have 19 responses/supervision area
  • 10. LQAS – Coverage estimates
    Information from supervision areas combined to obtain coverage for entire project area
    LQAS with information combined from multiple SAs is a form of stratified sampling where supervision areas are strata
    Requires a weighted average of all supervision areas; confidence intervals
    Total of 95 responses (5x19 = 95)
    Remember parallel sampling
  • 11. LQAS
    Useful for monitoring of implementation
    Can be controversial
    Best not to use for evaluation
  • 12. Controversy - Example
    Concern raised that use of LQAS to identify SAs as having reached the target, might result in mistakenly identifying an SA as one in for which resources can be reduced.
    If this is a mistaken classification, then the population will not receive needed resources
  • 13. American Statistical Association (ASA) Recommendation
    Report to the American Statistical Association Board of Directors on Lot Quality Assurance Sampling, August 19, 2010
    “We believe that LQAS conclusions should be carefully stated to ensure that the user will never mistakenly draw a conclusion about the performance of the SA. We propose the following as a better interpretation of the conclusions that can be drawn from LQAS:
    Based on considerations related to the power of the test employed, given the sample size used:
     
  • 14. ASA recommendation continued
    If 13 or more of the 19 samples of men in a supervision area (SA) can correctly name the ways to prevent sexual transmission of HIV, then we classify the SA as not requiring priority intervention at this time or
    If 12 or fewer of the 19 sampled men in the SA can correctly name the ways to prevent sexual transmission of HIV, then we classify the SA as substandardrequiring immediate intervention.
  • 15. Articles
    Rhoda, Dale A., Soledad A. Fernandez, David J. Fitch, and Stanley Lemeshow (2010), LQAS: User Beware. International Journal of Epidemiology, 39:60-68
    Olives, C., M. Pagano, and J.J. Valadez (2010), Commentary: Understanding practical lot quality assurance sampling. International Journal of Epidemiology, 39: 69-71.
  • 16. Resources:
    MCHIP NGO/PVO support website: www.mchipngo.net
    Rapid Health Surveys Handbook (Public Health Institute)
    CORE website: (www.coregroup.org)
    KPC Trainer of Survey Trainers (TOAST)
    LQAS trainers guides
    LQAS protocol for parallel sampling
    LQAS FAQs