Nudging Preventive Screening Via Message Framing and Bundling

This study is a randomized controlled field experiment embedded in the medical institution Early Diagnosis Program in Chile. Participants with two exams pending (a cancer screening test and a chronic disease test for diabetes and dyslipidemia) will be randomly assigned across a 3 × 3 factorial design: three message framing conditions (Basic, Risk/Importance, Peace of Mind) crossed with three exam-type conditions (cancer screening only, chronic disease test only, or both exams). Participants with only a cancer screening pending will be assigned to the 3 framing conditions and be encouraged to get the cancer screening. In both cases, participants are assigned to each experimental arm at twice the rate of an additional arm receiving the standard message currently used by the medical institution. This standard-message arm is included for operational purposes, is not part of the pre-specified analyses, and is thus not described in the "Arms and Intervention" section (or counted for "number of arms").

Inclusion Criteria: * Patients are included in the study if they have at least one pending screening for breast, colorectal, cervical, and prostate cancer within the contact window-as determined by the medical institution-and a valid phone number on file. This selection occurs operationally before randomization, so inclusion criteria are effectively determined ex-ante. Exclusion Criteria: * Participants will be excluded from the analysis if the WhatsApp message was not successfully delivered, as reported by the third-party software used by the medical institution.