Tip of the Week Archive

Incorrect reporting of study Arms due to duplicate counting of participants is a common “Major Issue” cited by PRS reviewers. If you have counted individual participants in more than one study arm, you’ll receive the following comment:

Major Issue: 1) Information in other parts of the record seems to indicate that Arms/Groups are not presented correctly; data should be presented separately for each Arm/Group in the study or a valid explanation provided.

 

Quick facts:

• Arms are the groups to which you assign participants.
• A participant can never be in more than one arm.
• Often, reviewers can’t tell that you’re Arms/Groups are presented incorrectly until you report your results.

 

When you report your results, the first module you fill out is Participant Flow. This shows how your participants in each Arm “flowed” through (or experienced) the study, including how many participants in each arm started and finished each “Period” of your study.

 

Once you enter data into the Participant Flow module, It’s easy to see if you double counted your participants by assigning them to more than one arm. Participants have been incorrectly double counted in the example table below:

 

Protocol Enrollment:		10 <-Actual enrollment, entered in the Protocol section of the record under Study Design. Here, this is the correct number.
Total Started in Participant Flow:		20 <-Total is calculated automatically from the number “Started” in Participant Flow in both groups. This is incorrect because participants were double counted in the Arms/Groups
Arm/Group Title	Drug A		Placebo	Total
Arm/Group Description	Drug A will be given at 100mg orally daily for 3 weeks		Placebo will be given at 100mg orally daily for 3 weeks
Period Title:Overall Study <- this is fine for some studies, but for studies with multiple intervention periods, like crossover studies, you need to add additional study periods.
Started	10		10	20
Completed	9		8	17
Not Completed	1		2	3

 

 

Fixing the problem

To resolve the issue, you must make sure you are assigning participants to only one arm. If you have assigned them to more than one arm because they are receiving more than one intervention (e.g. as in a crossover study), follow these steps:

 

1. Rename your arms so that they only describe one group of participants, and all the interventions that group will receive.

• Unacceptable Example: Arm 1: “Drug A”. Arm 2: “Placebo”
• Acceptable Example: Arm 1: “Drug A, then Placebo”. Arm 2: “Placebo, then Drug A”

   

  1. Add more “Periods” to your study (see below) to indicate when your participants in each arm were receiving each intervention.

 

Protocol Enrollment:		10
Total Started in Participant Flow:		10 <-Correct number, now matches Protocol Enrollment
Arm/Group Title	Drug A, then Placebo		Placebo, then Drug A	Total
Arm/Group Description	Drug A will be given at 100mg orally daily for 3 weeks, followed by a 1 week washout period, followed by Placebo at 100mg orally daily for 3 weeks		Placebo will be given at 100mg orally daily for 3 weeks, followed by a 1 week washout period, followed by Drug A at 100mg orally daily for 3 weeks
Period Title:First Treatment (3 Weeks) <- Multiple periods show when the participants in each group were receiving which intervention
Started	5		5	10 <-participants no longer double counted
Completed	4		5	9
Not Completed	1			1
Period Title:Washout (1 week)
Started	4		5	9 <-we can now see which participants started…
Completed	4		3	7 <-… and completed each period of the study
Not Completed			2	2
Period Title:Second Treatment (3 weeks)
Started	4		3	7
Completed	4		3	7
Not Completed

 

Contact [email protected] if you have any questions about how to use these modules or how to present your study arms.