The recruitment rate for clinical trials is calculated by multiplying the number of sites and randomized patients per site by the number of months of recruitment time. This number can also be reverse-engineered, starting with the number of randomized patients a trial needs.

Our clinical trial recruitment rate calculator formula below shows how many randomized patients per month should come from each site your trial is working with. To do this, you divide the total number of randomizations needed by the number of sites, and then multiply that by the length of the enrollment period in months. See below for a visual and some examples:

(total randomizations needed / number of sites) / months of enrollment period

So, for example, if a trial's goal was 20 randomizations from two sites over 5 months of enrollment, the calculation would look like this:

(20 / 2) / 5 = 10 / 5 = 2

Therefore, for this trial to be on schedule, the goal would need to be two patients, per site, per month.

Even with the best site selection plan in place, randomization rates can still fall lower than anticipated. According to research from Tufts, 11% of clinical trial sites fail to enroll a single patient.

Several different factors can cause recruitment challenges, such as limited patient databases at a site, unresponsive patient contacts, and complex protocols, which make a trial more difficult to recruit for than anticipated. Seasonality also can play a role in whether sites meet monthly targets. Patients may be less available for site visits during the year-end holiday season, for example. On top of all this, a major public health crisis like the COVID-19 pandemic greatly impacts clinical trial operations and safety.

When a trial first launches, it can take several weeks for a patient to consent and then randomize into a trial. A patient may first take an online screener and answer additional questions over the phone before reaching the site for a screening visit. Consider timing delays when calculating how many weeks it will take to reach your recruitment goals.

### How to conduct site feasibility for a clinical trial

Clinical trial site selection is an important step that can help prevent delays and other challenges once your trial is up and running. By thinking about patient recruitment first, you can help ensure that each site is in a position to enroll patients and meet its goals. Considering site experience, technological capabilities, and startup cycle times can also all help.

If you're using a site selection questionnaire to help make your decision, we recommend including the following points in your decision-making:

Think about your patient recruitment strategy before selecting sites. Sometimes, sponsors will wait to consider patient recruitment until all of the sites have already been identified. But choosing site locations that aren't convenient for patients or are too oversaturated with other trial options may contribute to delays in recruitment. Ask sites you're considering working with about their patient recruitment methods and metrics. Sites that maintain a patient database or work with patient recruitment companies may have a better chance of meeting recruitment timelines. Some recruitment companies can also help you with site selection based on data they have about patient populations and past trials.

Identify sites with experience running trials in your condition area. This criteria is particularly important for studies that usually have more complex protocols, such as Alzheimer's trials or oncology trials. If the site is already treating patients living with the condition, or has experience reaching out to those patients, it can reduce your patient recruitment efforts.

Find sites that use up-to-date technology. A site that uses the latest electronic data capture (EDC) and other technologies is more likely to be committed to innovation and change in all areas of running a trial. Modern technology can also help a site enroll and randomize patients faster, as well as collect more accurate data. According to a Tufts Center (CSDD) report, EDC compatibility issues, integration challenges, and technical demands are a problem for 77% of sponsors and contract research organizations (CROs). It's also important to note whether the site has the infrastructure you need to run your trial. Is the site equipped with the imaging devices, mobile devices, and other materials your trial requires? The clinical research industry has pivoted toward decentralized and virtual trials due to the circumstances of COVID-19. With so many trials delayed, virtual trials have been one of the only ways to complete ongoing studies on time.

Ask about the experience of the site's staff. When you visit or interview potential sites, ask about the experience of the staff and what kind of trials they've worked on in the past. Experienced site staff can also help ensure that your trial runs smoothly and on time.

Understand site startup cycle times. Look for cycle time rates in a few different categories: time from draft sponsor budget received to finalized budget; time from IRB submission to finalized materials; and time from contract fully executed to open for enrollment. Each of these cycle times can ultimately delay your trial, so it's important to find sites with strong numbers in each, or a plan to improve numbers.

The best way to avoid recruitment issues and delays is to use a variety of outreach methods and patient recruitment strategies from the start. Rather than relying on site outreach, it's critical to work with patient recruitment companies, connect with patient advocates, and deploy effective digital advertising to reach your goals on time. At Antidote, we call this approach precision recruitment. Learn more about how we accelerate timelines and help clients beat their recruitment targets by downloading our case studies below.