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--- food_allergy_definition [2022/07/01 12:37] – [Table] laura
+++ food_allergy_definition [2025/02/05 13:49] (current) – external edit 127.0.0.1
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 Researchers from the [[https://www.rug.nl/staff/j.m.vonk/|University Medical Center Groningen]] developed a definition of food allergy for all Lifelines participants (adults and children) using the [[allergies|allergy variables]] from [[2A]]. ([[sections]]: [[Diseases & symptoms]] ([[Allergies]]) and [[secondary & linked variables]]).\\
-The Food allergy definition can be requested in the Lifelines catalogue or by mail (data@lifelines.nl).\\
+The Food allergy definition can be requested in the [[https://data-catalogue.lifelines.nl/|Lifelines catalogue]].\\
 \\
 ===== Background =====
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 ===== Calculation of food allergy definition =====
+The calculation of the food allergy definition consisted of three steps: 1) coding of open text variables, 2) defining and calculating criteria to define food allergy, and 3) creating the overall food allergy variables.
+\\
+\\
+=== 1. Coding of open text variables ===
+At the start of the process, the responses from participants on "other allergen", "other reaction", and "other person who diagnosed the food allergy" are coded. The allergens and reactions were coded as //common//, //less common//, and //uncommon// using the tables as descibed by [[https://doi.org/10.1371/journal.pone.0231818|Westerlaken-van Ginkel et al. (2020)]]. These original coding tables were slightly changed after reachging consensus. The "other person" items have been coded into //alternative practitioner//, //other person//, and //no person mentioned//.
+\\
+\\
+=== 2. Defining and calculating criteria to define food allergy ===
+For adults, five criteria are included in the questionnaire, where the answers to these should not fall in the unlikely category. The unlikely answers are:
+  * **Criterium 1:** food allergy is only diagnosed by an alternative practitioner
+  * **Criterium 2:** the onset of symptoms after ingesting the food is after a day or more
+  * **Criterium 3:** the amount of food that elicits the reaction is a normal portion or more
+  * **Criterium 4:** the duration of the symptoms is longer than 1 week
+  * **Criterium 5:** a negative double blind placebo controlled food provocation test
+\\
+=== 3. Creating overall food allergy variables ===
+Food allergy was coded as //no food allergy (0)//, //indeterminate food allergy (1)//, and //likely food allergy (2)// according to the flow diagram provided in the paper of [[https://doi.org/10.1371/journal.pone.0231818|Westerlaken-van Ginkel et al. (2020)]].
-=== 1.  ===
+For children and adolescents only the two criteria have been asked. As a result, the food allergy definition is based on these two criteria only.For adults, it was decided to include two additional definitions of food allergy:
+  - A version without incorporating criterium 3 as there were many participants who reported a likely allergen and a likely reaction while the other four criteria were not unlikely.
+  - A version including only criterium 1 and 2, to make the definition comparable to the one for children and adolescents.
+\\
+=== Remarks from the UMCG researchers ===
+  - If a participant has two different questionnaires available, the quetsionnaire with the highest score on food allergy is selected.
+  - If a researcher wants to investigate food allergy in both children/adolescents and adults it is recommended to use //foodallergy_score_all_c_1//. If a researcher wants to investigate food allergy in adults only, it is recommended to use //foodallergy_score_adu_c_2// and use the //foodallergy_score_adu_c_3// variable in a sensitivity analysis.
+  - In the future the type of foods and the type of reactions will be classified and added.
+\\
 \\
 ===== Variables =====