Contacting Volunteers


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Every clinical researcher is familiar with the struggle of getting in contact with trial volunteers on the phone.

At Trialfacts we use the following method—and the results are still incredibly effective. The successful contact rate varies depending on volunteer demographics and other aspects of your study, but we’re typically able to get in contact with about 97% of the volunteers we’re trying to connect with.

Below is a step-by-step run-through of our method and why it works.

Phone Over Email

The faster you respond to your potential volunteers, the more likely they are to enroll in your study. The longer you put off replying or providing information, the greater the chance that person will lose interest or be talked out of it by a family member or a friend.

When it comes to contacting potential volunteers, phone calls are essential. Text messaging also tends to work really well, especially for younger demographics. However, important study information should only be shared on the phone or in person, when a person’s concerns can be addressed. Never relay any study information via email—the only role of email and texting is to get the volunteers on the phone or scheduled for an appointment.

The main benefit of a phone call is that it allows the volunteer to ask any questions or voice any concerns to a real human being. If you send lengthy emails with a lot of information, your volunteers will often not get around to reading them. If you’ve sent a lengthy email and then called your volunteer and s/he did not respond, one of the following things has happened:

  • They are avoiding your call because they have not had the time to read your email; or,
  • Questions (that they did not have anyone to answer) arose while reading the information presented in the email, so they assumed the worst and now you’ve scared them off and they do not want to answer.

In both of those cases, the task of getting back to you was put in the “too hard” basket, because they could not ask questions, and their concerns were not addressed.

Put the Volunteer’s Schedule First

Rather than calling a volunteer based on your specific schedule and guidelines and hoping they’re available, have the volunteer pick a time when they know they will be able to answer.

Again, remember that your volunteers are doing you a big favour in participating in your study, which is why it is very important to be respectful of your volunteer’s time and preferences. Your suggested meeting times, calling times, and appointment times should always suit the volunteer. This also means calling at the times you said you would call, and asking your volunteers which times suit them best. Always call your volunteers when they say they’re available. And yes, this means calling after hours or on the weekend when many people are much more readily available.

Most of us do not feel comfortable breaking a commitment if the other party holds up their end. So when volunteers agree to a given time and actually receive a call at that time, it feels like they’re breaking a commitment, which means they are much more likely to answer as they have made a commitment to do so.

Also, by presenting them with the option of choosing their own time, your volunteers will choose a time during which they know they will probably be available, and during which they are more likely to expect the call, and therefore answer an unknown number.

Limit the Contact Window

Allow volunteers to select a time to be contacted for the near future only (e.g. up to 3 days in the future). If volunteers make an appointment that is a week away, the appointment and your study will not be fresh in their minds. There is a greater chance they will forget about it, or the reasons why they wanted to participate in the first place.

Limiting the contact window fosters immediacy. The faster you respond to your potential volunteers, the more their interest in your study will increase, and the more likely they are to enroll in your study. The longer you put off replying or providing information, the greater the chance that person will lose interest or be talked out of it by a family member or a friend.

Send Reminders

At Trialfacts, we usually take it a step further than just letting our potential volunteers choose their contact time—we also send them a calendar invite and text messages reminding them that their call is coming up.

Thanks to the telemarketing industry, people are much less likely to accept phone calls from numbers they don’t recognise. However, when volunteers receive a reminder notification telling them you’ll be calling in 10 minutes, they’re not caught off guard by the unknown number when you actually do call at that time.

What’s even better than a generic reminder is to send volunteers a personalised reminder that will foster your volunteer-researcher relationship and build trust.

Call at the Expected Time

Keep in mind that asking people when they want to be contacted and not calling at that time significantly hurts your credibility. Since contacting the volunteer is the first one-on-one interaction they will have with anyone involved in the study, not calling at the promised time shows disrespect and significantly hurts the volunteer-researcher relationship.

Prove to the volunteer that you’re mindful of their time by calling them back when they’ve asked you to. Giving someone a call back when they’re expecting it goes a long way and establishes trust between you and the volunteer. If the person is sitting at home waiting for your call and the call never comes, it reflects negatively on you and your organisation, and makes it a lot less likely that the volunteer will enroll. It’s a big sign of respect and appreciation when you call your volunteers at the time they’ve chosen, which strengthens your volunteer-researcher relationship.


Medical issues are intimidating and trying a new clinical treatment that is still in the testing stages can be scary for some. Which is why a friendly and approachable face can make all the difference in getting volunteers to enroll in your study.

Adding human elements to your communication makes a big difference when it comes to building trust and the volunteer-researcher relationship. Without a personal touch, both the volunteer-researcher relationship and the volunteers’ interest in the study will evaporate. And one of the things you can do in order to establish a successful volunteer-researcher relationship is to personalise your communication with your volunteer, as well as put a friendly face on your organization.

Personalize Your Messages

People are more likely to accept calls from individuals than from an organization or a company; therefore, it’s essential to put emphasis on the person contacting the volunteer. Personalize your sign-up form with the calling representative’s name and photo—this way, your volunteers will realise that a real person is calling them.

Do not put emphasis on the organization when contacting volunteers—do not use terms like “us” or “the organization”. Referring to the organization alienates your contact and makes them unlikely to want to contact you back.

Instead, use a personalized approach. Make sure you include information that your volunteer has left about them, and mention it in your communication. If they’ve asked you to call them between 3 and 4 pm, mention it in your voicemail. If you’re running an asthma study and the volunteer mentioned in their message that their asthma is getting worse and this is why they’re interested in participating, mention it. Acknowledging the volunteer’s personal information or preferences builds trust and credibility and increases their chances of enrolling.

Below is an example of a voice message that references a single person, is personable and relatable, builds trust with the volunteer, and increases the chances that they will respond.


“Hi Tom This is Mandy from the Breathe study. I know you mentioned to call between 3 and 4 pm, so I thought I would try you now. I understand that your asthma symptoms have been getting worse, and I am sorry to hear that. I would love to hear more, so I will give you my mobile number, and you can call me anytime between 8am and 7pm.”

Be Consistent

Consistency provides credibility and builds trust. If the volunteer you’re trying to contact has already been passed around between three different people, they will feel like a small cog in a large machine, or they will feel like their contribution means very little. Which means that your volunteer’s interest will decrease and your volunteer-researcher relationship will suffer greatly if your volunteer does not feel appreciated.

This is why you should present a friendly, personal face to all your volunteers to build trust and credibility. This means providing them with a single contact that they can get to know, like, and trust. So make sure all your communication with an individual volunteer is always coming from the same person on your team—do not have several people call or send messages, as this will lower your chances of establishing a successful relationship with your volunteer.

Use a Personal Mobile Number

People are much more likely to answer when a call is coming from a number or an area code they recognise. So, it is extremely important to give volunteers a personal mobile number or at least contact them from a local number, and not a blocked or private number. For example, researchers based in the United States should use a number with a local city, state, or regional area code volunteers will recognize, while researchers based in Australia should use a mobile number (beginning with 04).

While it might seem daunting to give someone your mobile number, it really makes a difference in how likely volunteers are to pick up. A mobile number also puts a friendly, personal face that helps build trust between you and the volunteer. It also allows for a more flexible call schedule—if the volunteer is very busy during the day and can only call after hours, it’s important to be available during that time.

Send Personalised Reminders

After the volunteer selects their preferred appointment time for their call, send them a series of personalised reminders leading up to their chosen time. For example, we send a reminder email 24 hours in advance, an email and a text reminder an hour in advance, and a final text reminder 10 minutes in advance.

Make sure you always put your phone number in your email signature or your texts—this gives the person a way to contact you if they have any questions. Avoid using bulk sending services with opt-out messages at the bottom of your texts or emails, as these give the impression that you are contacting many people, so many that you are doing it in bulk, and their individual participation means little. Make sure your text messages sound like they’re coming from an actual person—any robotic-sounding messages do not inspire trust.


“Hi Tom! This is Mandy from the Breathe study! Thank you for choosing your appointment. I’ll leave you my mobile number in case you have any questions leading up to your appointment. Looking forward to speaking with you and have a great day.”

Be Diligent

People are busy and life gets in the way. While you don’t want to be hounding and bothering people, the reality is people give up trying to contact someone far too early. It’s important to be persistent and keep calling them until they answer. Remember: they’ve showed interest in your trial, so you’re following up on their interest. Don’t assume people aren’t interested in your trial just because they’re not picking up.

Keep in Mind Preferred Times

Pay attention to the volunteer’s preferred time. If they haven’t answered the first call, try to time your follow-ups to coincide with the preferred time. By making sure the times are always convenient for your volunteers, they’ll feel like you’re accommodating them, which makes them feel valued and appreciative.

Be Persistent

Persistence is key. If the volunteer does not pick up the phone when you call them at the designated time, be relentless in following up. If they do not answer the phone call, make sure to follow up with a text message. If they still haven’t answered, leave one or at most two days before trying again. Keep calling until they have to pick up the phone. If the recruitment deadline is in less than a week, try once or twice a day.

Remember that it is very easy for volunteers to say they’re not interested, especially via text message So don’t make the mistake of assuming your volunteers’ level of interest until they actually tell you they’re not interested, or until you’ve called them and left text message and/or voicemails ten times.

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