ENBIS-16 in Sheffield

11 – 15 September 2016; Sheffield Abstract submission: 20 March – 4 July 2016

Effects of Imperfect Testing on Presence-Absence Sampling Plans

12 September 2016, 10:00 – 10:20


Submitted by
Edgar Santos Fernandez
Edgar Santos-Fernández (Massey University), K. Govindaraju (Massey University), Geoff Jones (Massey University)
Sampling inspection plans are used in the food industry to determine whether a batch of food is contaminated or not. Testing for pathogens is mandatory in several foodstuffs because some pathogenic bacteria pose a significant risk for human health, even when these are consumed in minute quantity. Test performance measures such as sensitivity and specificity are generally ignored in microbiological risk assessment. In this presentation, we examine the impact of imperfect analytical tests on sampling inspection plans for presence-absence characteristics. We discuss several plausible scenarios and assess the risk for the consumers. The method is illustrated using collected data over two years for Cronobacter spp. in skimmed milk powder. The probability of contamination and the test sensitivity and specificity, are estimated using Bayesian inference. We examine the sampling plans proposed by the Codex Alimentarius and by New Zealand's Ministry of Primary Industries. A cost analysis is carried out to show the economic loss due to measurement errors. We describe the strengths and limitations of these inspection plans under different conditions and propose a plan that could provide better protection to the consumers as well as to the producers.
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