Related Experiment Video
Updated: Feb 25, 2026

Detection of Foodborne Bacterial Pathogens from Individual Filth Flies
Published on: February 13, 2015
APPLICATION OF STRATIFIED ANALYSIS IN EPIDEMIC INVESTIGATIONS : ANALYSIS OF AN OUTBREAK OF FOOD POISONING
Abstract:
The present study demonstrates the use of stratified analysis when high (or low) risk is observed for two or more food items during the investigation of food poisoning, rather than simply implicating the item showing the highest risk. In this study an outbreak of food poisoning, which exhibited a clinico-epidemiological profile of Clostridium perfringens as the possible agent, was investigated using a case-control typology. Evaluation of food histories showed a high and significant odds ratio (OR) for a mutton dish (OR = 6.45, p < 0.001) and peas dish (OR = 5.6, p < 0.001), while a legume dish showed a protective effect (OR = 0.13, p < 0.001) which proved erroneous. Stratified analysis using Mantel-Haenszel procedure indicated that the risk due to mutton persisted even after adjusting for consumption of peas (adjusted OR = 4.22) or legume dish (adjusted OR = 4.25). The use of stratified analysis in investigating epidemics has been recommended.
Related Concept Videos
Steps in Outbreak Investigation
Introduction to Epidemiology
Statistical Methods for Analyzing Epidemiological Data
Stratified Sampling Method
To choose a stratified sample, divide the population into groups called strata and then take a...
Comparing the Survival Analysis of Two or More Groups
Strategies for Assessing and Addressing Confounding
Confounding can be addressed at both the design phase of a study and through analytical methods after data...

