Front-end checks, also known as online or real-time checks, are validations built directly into the data entry interface (e.g., an Electronic Case Report Form). They are designed to verify data as it is being entered into a field, such as a text box. This provides immediate feedback to the user, allowing for on-the-spot correction of simple errors like incorrect data formats, out-of-range values, or missing data. Implementing checks at the front-end is a fundamental strategy for preventing data entry errors at the source and improving initial data quality before the data is even submitted to the database.

A. Manual Check: This is a human review of data listings after data has been entered and submitted, not an automated check implemented within a text box.

B. Back-end check: These checks run on the server after data has been submitted. They are typically used for more complex, cross-form, or cross-visit validations, not for immediate feedback in a text box.

D. Programmed check: This term is too general. While a front-end check is a type of programmed check, "front-end" is the more specific and accurate answer describing validation at the point of entry.

1. Society for Clinical Data Management (SCDM). (2023). Good Clinical Data Management Practices (GCDMP). Section 5.6.2, Edit Checks: "Edit checks can be programmed to fire at the time of data entry (i.e., real-time or front-end checks) or after the data has been entered into the database (i.e., batch or back-end checks)."

2. Krishnankutty, B., Bellary, S., Kumar, N. B. R., & Moodahadu, L. S. (2012). Data management in clinical research: An overview. Indian Journal of Pharmacology, 44(2), 168–172. https://doi.org/10.4103/0253-7613.93842. (This article discusses data validation processes, noting that in EDC, "the data is entered at the site and the edit checks are fired simultaneously," which describes the function of front-end checks.)

3. Lualdi, C., et al. (2021). Data Quality in Clinical Research: A Methodological Review of the State of the Art. Journal of Medical Internet Research, 23(10), e28948. https://doi.org/10.2196/28948. (The paper discusses data quality controls, including "automated edit checks at the time of data entry" as a key method for preventing errors, which is the definition of a front-end check.)