# Dechallenge computation

In the section “Time-to-onset, dechallenge, rechallenge and causality of suspect and
\
interacting drugs”, the information about dechallenge is computed from different data
\
elements to get a quick overview. The action taken with the drug together with the reaction
\
outcome are translated into *Dechallenge performed (Yes/No/Unknown) and Reaction*
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*resolved/resolving* (Yes/No/Unknown)

#### *Dechallenge performed is set to*

* **yes**, if the action taken with the drug is “Drug withdrawn” or “Dose reduced”
* **no**, if the action taken with the drug is “Dose increased” or “Dose not changed”
* **unknown**, if the action taken with the drug is “Unknown”
* blank, if the action taken with the drug is “Not applicable”

#### *Reaction resolved/resolving is set to*

* **yes**, if the outcome of the reaction is “recovered/resolved”, “recovering/resolving” or
  \
  “recovered/resolved with sequelae”
* **no**, if the outcome of the reaction is “not recovered/not resolved” or “fatal”
* **unknown**, if the outcome of the reaction is “Unknown”

Reaction resolved/resolving is only set if there is a reported value for action taken with the
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drug.

If none of the above is true, then free text from the data element drug additional is used. This
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is mainly to capture dechallenge information from case reports where we know this is not
\
reported within the structured fields but rather as specific text strings.

* When drug additional is “DECHALL POS” then *Dechallenge performed* is set to **yes** and *Reaction resolved/resolving* is set to **yes**
* When drug additional is “DECHALL NEG” then *Dechallenge performed* is set to **yes** and *Reaction resolved/resolving* is set to **no**
* When drug additional is “DECHALL RESULT UNK” then *Dechallenge performed* is set to **yes** and *Reaction resolved/resolving* is set to **unknown**


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