A longitudinal, descriptive study was conducted, in which a biennial organized screening program for CRC was designed, utilizing the fecal immunochemistry test (FIT). The participants were selected through convenience sampling.

Subjects over 50 years of age and residents of Veracruz, Mexico, that were considered to have an average risk for developing CRC and who expressed an interest in participating in the screening program, were recruited between January and June 2019. Participants were selected by means of conferences on CRC directed at workers and academic personnel from different dependencies of the Universidad Veracruzana. The exclusion criteria were age above 80 years and having a high risk for CRC, terminal or decompensated illnesses, or signs of recent bleeding. The eligible individuals were scheduled to be seen by a team of physicians trained in screening for CRC.

All participants were personally interviewed by physicians trained in CRC screening, to provide information on prevalence, etiology, adenoma-carcinoma sequence, screening methods, recommended time intervals, and challenges regarding adherence. Likewise, a written questionnaire was applied to collect information on age, sex, body mass index (BMI), alcoholism, smoking, physical activity, and nonsteroidal anti-inflammatory drug (NSAID) use.

To detect fecal occult blood, the participants were given a screening kit that included a container for collecting the sample, an instruction pamphlet, and a quantitative FIT (OC FIT-CHEK®, Polymedco, Cortlandt Manor, NY, USA). The participants were asked to collect the stool sample and return the FIT kit within the next three days. All samples were processed by a central laboratory utilizing an automated testing method recommended by the manufacturer (Eiken Chemical, Tokyo, Japan). To define an abnormal FIT result, and then refer those patients to colonoscopy, a cutoff point >100 ng of hemoglobin/mL of buffer ( = 20 μg of hemoglobin/g from stool) was used. The patients with abnormal results were contacted via telephone to personally receive their results and continue with the next step of screening. Colonoscopies were performed by an experienced, certified endoscopist. Polypectomy with biopsy was carried out, when indicated, and the results were reviewed by a pathologist with expertise in the gastrointestinal tract. Within the study methodology, specific time periods were established to manage positive results and schedule the colonoscopies. One week after a positive result was obtained, direct contact was made with the patient. Colonoscopy was then scheduled and performed, no later than one month after having informed the patient that the procedure was necessary. All the patients received their results and follow-up recommendations from the general physician. The patients with adenomas were referred to the gastroenterology service for individualized medical and endoscopic follow-up.

To improve CRC screening program adherence, an intervention was implemented that included the training of a team of five patient navigators, who were pre-graduate physicians. The training was carried out by a gastroenterologist, who gave specialized talks on different aspects related to CRC.

The talks included the themes of risk assessment for CRC, the different screening methods available, the use of effective communication tools, and intercultural learning. The aim of the training was to provide the patient navigators with the knowledge necessary for offering the screening program participant comprehensive and quality advice.

In addition to the training, as part of the intervention, a detailed telephone call script was designed and used by the patient navigators to contact the participants of the 2019 screening program and invite them to participate again in the 2021 program, within the time frame of January to June.

The cellphone call patterns were registered according to the response obtained as “answered”, “rang but no answer”, “outside of the area of cellphone service”, “call went to voicemail”, “wrong number”, “nonexistent number”, “participant not interested”, and “participant no longer living”. Likewise, the biennial participation patterns were registered, identifying participant adherence as follows: “consistent adherence” (for those that attended the biennial screening), “inconsistent (late) adherence”, and “no adherence”.

The participants that attended their 2021 biennial screening round received personalized attention from their assigned navigator, who once again gave them detailed information about CRC and the different screening methods available and answered their questions. At the end of the interview, the general physician explained the sample collection process and provided additional feedback on the aspects previously discussed. The remainder of the screening process was carried out with the same methodology utilized during the first screening round.

The stratification of attendance to the biennial screening round was calculated, considering the previous participation of the individuals. In addition, the different participation permutations were described (consistent, inconsistent, nonexistent).13 To calculate biennial adherence, only the participants that concluded the screening process through the FIT in the two consecutive years (consistent participants) were considered. The formula employed for calculating consistent biennial adherence was: (number of subjects that met the criterion)/(total number of initial participants).

Data distribution was evaluated using the Kolmogorov-Smirnov test. The numerical variables were reported as median and interquartile range, and the categorical variables were expressed as frequency and percentage. The consistent adherence rate was calculated by dividing the number of participants with consistent biennial adherence by the total of initial participants. The groups were compared using the Student’s t test or the Wilcoxon test, as applicable. The chi-square test or Fisher’s exact test were utilized for the categorical variables. The analysis was carried out using the SPSS (IBM, Armonk, NY, USA) V.24 program.

This protocol was evaluated and accepted by the scientific ethics committee with folio llMB-2019-03 and was carried out in accordance with the principles of the Declaration of Helsinki. All the subjects participated voluntarily, free of charge, and signed statements of informed consent, in which the procedure and risks and benefits of the study were explained. The results were also explained and sent to the participants, either by email or in printed form. The subjects with abnormal results were referred to the corresponding health services for diagnosis or early treatment. All tests were carried out free of charge for all the study participants.

In 2019, a total of 301 subjects, 73.4% of whom were women, arrived at our institution. They received a FIT kit and were personally interviewed by the corresponding patient navigator. The median age of the participants was 61 years, with a range of 55–68 years. Of the participants, 277 (92%) returned the FIT kit exactly as requested. Upon analyzing the returned FIT kits, 13 (4.3%) were found to be positive. Eleven colonoscopies were consequently performed, revealing adenoma in 36.3% of the cases. A description of the evaluation results of the adenomas found in the patients follows below.

Patient 1: A 62-year-old man. Four adenomas with low-grade dysplasia were identified, located in different segments of the colon, including the ascending colon, transverse colon, descending colon, and sigmoid colon. In addition, the presence of mild chronic colitis was observed, accompanied by marked eosinophilia, registering up to 43 eosinophils in a high-power field.

Patient 2: A 65-year-old woman. Three tubular adenomas with low-grade dysplasia in the cecum, transverse colon, and descending colon were found.

Patients 3 and 4: A 57-year-old woman and a 68-year-old woman, respectively. Both presented with a single adenoma, with low-grade dysplasia, in the descending colon.

In 2021, the initial cohort was followed, excluding the patients that did not return their FIT kit. The remaining 277 participants, 72.8% of whom were women, were contacted by cellphone. Three interventions via cellphone were carried out, with a maximum of 3 calls attempted per subject, with a one-week interval between calls. In the first intervention, a total of 396 calls were made, establishing effective contact with 179 subjects (45.2%). Of those contacts, a FIT kit was given to 93 patients, representing 52% of the contacts and 23.4% of the calls made. In the second intervention, 191 calls were made, achieving successful contact with 84 subjects (44%). Of those successful contacts, a FIT kit was given to 31 patients, the equivalent of 37% of the subjects contacted and 16.2% of the calls made. Lastly, in the third and final intervention, 160 calls were made, achieving effective contact with 24 subjects (15%). A FIT kit was given to eight patients, representing 33.4% of the subjects contacted and 5% of the calls made.

In summary, a total of 747 calls were made throughout the study, with a 38.4% success rate (287 effective calls) and a 61.6% failure rate (460 ineffective calls). The ineffective call patterns were distributed as follows: 34.1% of the calls were not answered by the recipient, 30.6% calls were sent to voicemail, 25.2% calls could not be connected because the recipient was out of the area of cellphone service, 5.8% calls corresponded to a nonexistent number, 2.8% calls were to a wrong number, 0.6% of the recipients were not interested in participating in the study, and 0.6% of the recipients had already died. Table 1 summarizes those findings.

Of the 277 subjects eligible for undergoing the biennial screening, 199 (74.8%) were contacted. Of those subjects, 143 came to our institution to pick up their FIT kit and 126 (88.1%) returned it.

According to the previous participation of the eligible subjects (n = 277), 45.5% (n = 126) participated again in the 2021 screening program. Upon analyzing the different attendance permutations of the initial cohort (n = 301), the following results were obtained: 41.8% (n = 126) of the subjects attended the two screening rounds, 51.2% (n = 154) only attended the first screening round, 2% (n = 6) only attended the second screening round, and 5% (n = 15) did not attend either of the screening rounds.

Regarding the attendance patterns, 126 subjects (41.8%) maintained consistent attendance in the two screening rounds, whereas 160 subjects (53.2%) presented with inconsistent attendance (attending one screening round but not the other). In addition, 15 subjects (5%) were identified that did not attend either screening round.

Upon concluding the study, of the 301 initial subjects, a total of 126 successfully completed their biennial screening with a FIT, resulting in a consistent adherence rate of 41.8%. Table 2 shows the epidemiologic characteristics of participants with adherence and nonadherence.