User Tools

Site Tools


multiple_choice_questions_in_cdisc_odm

This is an old revision of the document!


Multiple Choice Questions in CDISC ODM

We regurarly get questions about “multiple choice” or “check all that apply” questions in CDISC ODM, i.e. questions that seemingly have a codelist, but for which it is allowed to check or select more than one answer.

Consider the question: “Did you suffer any of the following tropical diseases in the last five years? Please check all that apply”

  • Chagas disease
  • Dengue
  • Leishmaniasis
  • Malaria
  • Onchocerciasis (river blindness)
  • Schistosomiasis (snail fever)

The ODM specification does not tell us how to treat such questions. Obviously, we cannot use a CodeList, as there is also a rule that states that within an ItemGroupData, the same ItemOID may only occur once.

So, what can we do?

In such cases, it is always a good idea to take a step back and go back to the basics. What is a multiple-choice list?

So the following is not allowed:

<ItemGroupData ItemGroupOID="...">
  <ItemData ItemOID="**IT.TROPICAL_DISEASE**" Value="Malaria"/>
  <ItemData ItemOID="**IT.TROPICAL_DISEASE**" Value="Schistosomiasis"/>
</ItemGroupData>

Also using a list of comma-separated values is not a good idea, as the value itself may contain a comma. So the following is also not good:

<ItemGroupData ItemGroupOID="...">
  <ItemData ItemOID="IT.TROPICAL_DISEASE" Value="Malaria, Schistosomiasis"/>
</ItemGroupData>

Essentially, it is a list of items for which each can have the value “true” or “false”, e.g. “Yes” I did have malaria, and “No”, I did not have Dengue. So let us treat this as a list of items with boolean values! ODM does support the “boolean” data type as of v.1.3. So we could write the following in the “Study” part of the ODM:

<ItemDef OID="IT.CHAGAS" Name="Chagas disease" DataType="boolean"/>
<ItemDef OID="IT.DENGUE" Name="Dengue" DataType="boolean"/>
<ItemDef OID="IT.LEISHMANIASIS" Name="Leishmaniasis" DataType="boolean"/>
<ItemDef OID="IT.MALARIA" Name="Malaria" DataType="boolean"/>
<ItemDef OID="IT.ONCHORCIASIS" Name="Onchocerciasis (river blindness)" DataType="boolean"/>
<ItemDef OID="IT.SCHISTOSMIASIS" Name="Schistosomiasis (snail fever)" DataType="boolean"/>

Essentially, it is besser to explicitely have the question itself in the “Question” child element, especially when the study runs in several countries with different languages. For example:

<ItemDef OID="IT.SCHISTOSMIASIS" Name="Schistosomiasis (snail fever)" DataType="boolean">
  <Question>
    <TranslatedText xml:lang="en">Schistosomiasis (snail fever)</TranslatedText>
    <TranslatedText xml:lang="de">Schistosomiasis (Bilharziose)</TranslatedText>
  </Question>
</ItemDef>

Now, at first sight, this might seem to be a bit tricky, as we have to group Items to ItemGroups, using “ItemRef”. So:

<ItemGroupDef OID="IG.TROPICAL_DISEASES" Name="Tropical Diseases">
  <ItemRef ItemOID="IT.CHAGAS" Mandatory="Yes"/>
  <ItemRef ItemOID="IT.DENGUE" Mandatory="Yes"/>
  <ItemRef ItemOID="IT.LEISHMANIASIS" Mandatory="Yes"/>
  <ItemRef ItemOID="IT.MALARIA" Mandatory="Yes"/>
  <ItemRef ItemOID="IT.ONCHORCIASIS" Mandatory="Yes"/>
  <ItemRef ItemOID="IT.SCHISTOSMIASIS" Mandatory="Yes"/>
</ItemGroupDef>

Now, as you have see I have set “Mandatory” to “Yes” in each case. This ensures that in the ClinicalData, there MUST be an ItemData for each of the six items, each containing a value of “true” or “false”. The best way to implement this in a form would be to have two checkboxes after each question with the choices “Yes” and “No”. Like that, I am sure that the subject did not forget an item, i.e. really thought about it whether he/she has suffered of the specific disease in the last first years. If I had set the “Mandatory” to “No”, there does not have to be an “ItemData” for each question, but I could then implement it as having only one checkbox after each disease item, which is checked when the patient has suffered from the disease.

Personally, I prefer the former, as it is clearer and ensures that the subject really looked at each of the items. I.e. the data quality will be better.

Now, you will say “where is the overal question 'Did you suffer any of the following tropical diseases in the last five years?'”?

Well, that can be described in the “Description” element of “ItemGroupDef”. For example:

<ItemGroupDef OID="IG.TROPICAL_DISEASES" Name="Tropical Diseases">
  <Description>
    <TranslatedText xml:lang="en">Did you suffer any of the following tropical diseases in the last five years?</TranslatedText>
    <TranslatedText xml:lang="de">Haben Sie sich an eine der folgenden Krankheiten erkrankt in den fünf letzten Jahren?</TranslatedText>
  </Description>
  <ItemRef ItemOID="IT.CHAGAS" Mandatory="Yes"/>
  <ItemRef ItemOID="IT.DENGUE" Mandatory="Yes"/>
  <ItemRef ItemOID="IT.LEISHMANIASIS" Mandatory="Yes"/>
  <ItemRef ItemOID="IT.MALARIA" Mandatory="Yes"/>
  <ItemRef ItemOID="IT.ONCHORCIASIS" Mandatory="Yes"/>
  <ItemRef ItemOID="IT.SCHISTOSMIASIS" Mandatory="Yes"/>
</ItemGroupDef>
multiple_choice_questions_in_cdisc_odm.1389644492.txt.gz · Last modified: 2014/01/13 21:21 by manager