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Good review practice: a researcher guide to systematic review methodology in the sciences of food and health

Framing the question

Framing the question

The first and most important step in conducting a systematic review is framing the research question. The aim of this process is to break down the research question/issue into its main components or “key elements”. The key elements specify relevant concepts of a topic and set the boundaries for the study. 

An effective method of identifying the key elements is using a standard framework in relevance to the question type. The most used frameworks are the followings: POPECO/ PICO, PEO, PICOTThe acronyms PIEO and T stand for the following key elements: Population, Intervention or Exposure, Comparator, Outcome, and Timeframe.  These frameworks were first created for healthcare studies but can be adopted and used in other food-related contexts.

The details for formulating different question types are laid out below for each framework:

Descriptive questions

Descriptive questions

This framework can be adopted to measure frequency of a variable among a target population for incidenceoccurrence, and prevalence questions. Epidemiological studies may assess the changes over time and therefore factor a specific timeframe for the study (POT). In those cases, the framework POT is adopted.

Effectiveness/effect and exposure questions

Effectiveness/effect and exposure questions

The framework PICO can be used to measure the effect of deliberate interventions or exposures in different contexts. It can be used for assessing effectiveness and dose-dependent relationships for the state or extent of the variables. For instance, when an extent of a relationship between a food product and human health outcomes is evaluated PICO frameworks can be used. See examples in the table below.

Test accuracy questions:

Test accuracy questions:

Assessing accuracy relates to those research questions about sensitivity and accuracy of tests or analytical methods. In clinical topics diagnostic methods are reviewed for accuracy using PIT framework. In food related topics the accuracy of an analytical method for detection or quantification of a chemical in food products or a pathogen in plant-based or animal foods can be evaluated against a reference index using the PIT framework.

The SPICE framework:

The SPICE framework

The acronym represents Setting, Perspective or Population, Intervention, Comparator and Evaluation method. It is a common approach in formulating broader practice questions that are aimed at evaluating outputs and impacts. It is used in framing questions within social and environmental sciences.

Question examples

Question examples