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FSIS

Web Content Viewer (JSR 286)

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Web Content Viewer (JSR 286)

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Web Content Viewer (JSR 286)

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Web Content Viewer (JSR 286)

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Web Content Viewer (JSR 286)

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Sampling Results for FSIS Regulated Products

Related Documents and Data Tables

FSIS calculates prevalence, volume weighted percent positive, or percent positive calculations for microbial pathogens in FSIS regulated products that are currently sampled through existing sampling projects. [1],[2] FSIS evaluated its sampling projects in 2012 to determine if they could be used to calculate prevalence; this evaluation was used to guide the development of these calculations. [3],[4] FSIS intends to provide new calculations each quarter using the prior 12 months of sampling data.[5]

Overview

Depending on the data available, calculations will either be percent positives, volume-weighted percent positive, or prevalence.[6] When possible, the calculations will include upper and lower confidence bounds.

  • Percent positive (PP) – The percentage of samples of a specific FSIS-regulated product with a specific pathogen. These calculations may vary significantly from the actual prevalence of the population, but FSIS cannot make a more precise calculation with the data currently available.
  • Volume weighed percent positive (VWPP) – The VWPP for a specific product-pathogen pair is calculated by combining the production volumes (production volume can be defined as the amount (weight or numbers of head) of product produced per year) for establishments with their sampling results. This provides a more accurate estimation than a percent positive, but the data do not meet the statistical requirements to make a prevalence estimate. VWPP is more public health focused than PP, in that weighting results by volume reflects exposure of the public to specific pathogens.
  • Prevalence– The estimated proportion, nationally, of a specific FSIS-regulated product with a specific pathogen.


[1] Current calculations are based only on domestically produced product collected at FSIS regulated establishments under routine sampling projects. FSIS is looking into the possibility of including import and retail sampling data. Follow-up samples from previous positives are not included.

[2] Current calculations are national estimates for all establishment sizes. FSIS does not believe that the data support calculations based on smaller geographic regions or establishment size at this time.

[3] This evaluation, Use of FSIS Regulatory Verification Sampling to Generate Prevalence Estimates, is available on the FSIS website. Use of FSIS Regulatory Verification Sampling to Generate Prevalence Estimates

[4] FSIS has made modifications to several of its sampling projects since this evaluation was published. These modifications were made both to improve verification and to allow more precise calculations. Details of these changes can be found in the FSIS annual sampling plans available on the FSIS website.

[5] The sampling projects for raw pork, raw chicken, and raw turkey all started or had significant changes during FY2015. The first date of available data is noted for each calculation. Once a full year’s data is available, all calculations will be based on one year of data.

[6] For each product pathogen pair, FSIS chose the most statically valid method. Factors that impacted this decision are: the dates of sampling results; the number of samples available; the sampling design, or some other property of the sampling project that limits the conclusions that can be drawn from the aggregated sampling results. The different types of calculations should not be compared.

 

Last Modified Jul 28, 2017