A study will enroll 420 subjects over 3.5 years. What is expected average monthly accrual?

The calculation for the average monthly accrual rate is a fundamental aspect of clinical trial project management. To determine this rate, the total number of subjects to be enrolled is divided by the total duration of the enrollment period in months.

First, convert the enrollment period from years to months:

3.5 years × 12 months/year = 42 months

Next, divide the total number of subjects by the total number of months:

420 subjects ÷ 42 months = 10 subjects/month

Therefore, the expected average monthly accrual is 10 subjects.

A. 9: This accrual rate would result in only 378 subjects (9 subjects/month × 42 months), failing to meet the study's enrollment target of 420.

C. 11: This accrual rate would lead to enrolling 462 subjects (11 subjects/month × 42 months), exceeding the target and potentially impacting the study's budget and statistical power calculations.

D. 19: This rate is a significant overestimation, resulting in 798 subjects (19 subjects/month × 42 months), which is nearly double the required sample size.

1. Society of Clinical Research Associates (SOCRA). Certification Program for Clinical Research Professionals: Detailed Content Outline. Section IV. Study and Site Management, Subsection A. Site Management, Points 4 & 5. This outline specifies that a core competency for a CCRP includes the ability to "Develop and monitor a recruitment plan" and "Monitor enrollment goals," for which calculating the required accrual rate is a foundational skill.

2. Meinert, C. L., & Tonascia, S. (2012). Clinical Trials: Design, Conduct, and Analysis (2nd ed.). Oxford University Press. Chapter 9, "Patient Recruitment and Retention," discusses the critical importance of establishing realistic recruitment goals and timelines. The calculation of monthly accrual is a primary step in this process.

3. Spilker, B. (1991). Guide to Clinical Trials. Raven Press. Chapter 58, "Recruiting Patients for Clinical Trials," pp. 511-524. This chapter details the planning phase of recruitment, which involves estimating the rate at which subjects can be enrolled (accrual rate) to determine the feasibility and duration of a trial.

4. Duke University School of Medicine. Clinical Research Training Program Courseware. Module: "Study Feasibility and Site Selection." The course materials emphasize that a key component of a feasibility assessment is calculating the required enrollment rate based on the target sample size and timeline, and comparing it against the site's potential pool of participants.