Identifying the best cutoff value of the fecal occult blood immunochemical test in the detection of advanced and neoplastic colorectal lesions.

Objective: Screening is an effective tool for detecting colorectal lesions in asymptomatic subjects. There is a positive correlation between fecal immunochemical test (FIT) values and the size of tumors. Despite the efficacy of screening, the detection of colorectal cancer (CRC) remains low. The primary objective was to evaluate the best FIT cutoff value for detecting advanced adenomas and CRC among individuals at average risk in a country with a high incidence and morbidity from CRC. Methods: This observational and prospective study analyzed consecutive cases in 1461 asymptomatic subjects with a positive FIT (≥ 100 ng hemoglobin [Hb]/mL) referred for colonoscopy (2012-2015) at a tertiary center in Uruguay. Results: Colorectal lesions were detected in 35.3% (516/1461) of cases, with a mean age of 62.8 ± 8.3 years. About 53.2% were men and 65.1% of the tumors were located in the left side of the colon. The size of the lesion and FIT values (p = 0.001) were positively correlated. Laterally spreading tumors predominated in the right colon (586 ng Hb/mL; 95% Confidence interval [CI] 443.4-760). One hundred and thirty-five (26%) lesions were advanced adenomas (15 ± 6.7 mm); 694.6 ng/mL; 95% CI 632.4-756.9). The highest diagnostic yield (0.5112) for advanced adenomas was at a FIT level of 400 ng Hb/mL (accuracy 88.6%). There were significant differences in FIT values early and advanced CRC (927 ng/mL; [95% CI: 637-1082] vs. 1453 [95% CI: 1352-1594; p = 0.001]). Conclusion: A FIT value of 400 ng Hb/mL was the best diagnostic yield to detect advanced adenomas and CRC. This value is useful during the COVID-19 pandemic as it allows prioritization of colonoscopy to those most at risk of significant disease, thus reducing risks to both patients and healthcare workers.

Objetivo: El cribado es una herramienta eficaz para detectar lesiones colorrectales en sujetos asintomáticos. Existe una correlación positiva entre los valores de la prueba inmunoquímica fecal (FIT) y el tamaño de los tumores. A pesar de la eficacia del cribado, la detección del cáncer colorrectal (CCR) sigue siendo baja. El objetivo principal fue evaluar el mejor valor de corte FIT para detectar adenomas avanzados y CCR entre personas con riesgo promedio en un país con alta incidencia y morbilidad por CCR. Métodos: Este estudio observacional y prospectivo analizó 1461 sujetos asintomáticos con FIT positivo (≥ 100 ng de hemoglobina [Hb]/mL) remitidos para colonoscopia (2012-2015) en un centro terciario en Uruguay. Resultados: Se detectaron lesiones colorrectales en el 35,3% (516/1461) de los casos, con una edad media de 62,8 ± 8,3 años. Alrededor del 53,2% eran hombres y el 65,1% de los tumores estaban ubicados en el lado izquierdo del colon. El tamaño de la lesión y los valores FIT (p = 0,001) se correlacionaron positivamente. Los tumores con extensión lateral predominaron en el colon derecho (586 ng Hb/mL; intervalo de confianza [IC] del 95%: 443,4-760). Ciento treinta y cinco (26%) lesiones fueron adenomas avanzados (15 ± 6,7 mm); 694,6 ng/ml; IC 95% 632,4-756,9). El rendimiento diagnóstico más alto (0,5112) para los adenomas avanzados se obtuvo con un nivel FIT de 400 ng Hb/ml (precisión del 88,6%). Hubo diferencias significativas en los valores de FIT de CCR temprano y avanzado (927 ng/mL; [IC 95%: 637-1082] vs. 1453 [IC 95%: 1352-1594; p = 0,001]). Conclusión: Un valor FIT de 400 ng Hb/mL fue el mejor rendimiento diagnóstico para detectar adenomas avanzados y CCR. Este valor es útil durante la pandemia de COVID-19, ya que permite priorizar la colonoscopia a aquellos con mayor riesgo de padecer una enfermedad importante, reduciendo así los riesgos tanto para los pacientes como para los trabajadores de la salud.

Results of the fecal immunochemical test in a colorectal cancer screening program in Mexico.

BACKGROUND: Colorectal cancer (CRC) is one of the main five causes of morbidity and mortality by oncologic diseases in our country and worldwide. Recently, fecal immunochemical test (FIT) has proven to be a noninvasive screening test that allows to select patients most likely to have a pre-malign lesion in order to perform a colonoscopy. OBJECTIVE: To report the findings of a CRC screening program using FIT in our country population. METHOD: A multicentric study was performed, by inviting open population older than 50 years to participate in a CRC screening. Quantitative FIT specific for human hemoglobin was used, with a cut point of 100 ng/ml or higher to consider as positive. Those patients with positive results were asked to undergo a colonoscopy. In the cases where polypoid lesions were found, biopsies were performed. RESULTS: In total, 751 FIT were processed, and 51 (6.8) of those were positive, with a rate of 15.9 premalign lesions for 1,000 individuals, and 1.3 patients with CRC for every 1,000. CONCLUSIONS: The present study matches worldwide reports, supporting the initiative of establishing a formal and standardized CRC screening program in the public health sector.

ANTECEDENTES: El cáncer colorrectal (CCR) es una de las cinco primeras causas de morbimortalidad por cáncer en nuestro país y en todo el mundo. La prueba inmunoquímica fecal (FIT, fecal immunochemical test) es una herramienta de tamizaje no invasiva que permite seleccionar a los sujetos con mayor probabilidad de lesión premaligna en la colonoscopia. OBJETIVO: Reportar los resultados del programa de escrutinio para CCR mediante FIT en población abierta en México. MÉTODO: Estudio multicéntrico nacional en población abierta mayor de 50 años a través de medios de difusión masiva para participar en un programa de escrutinio de CCR. Se utilizó FIT cuantitativa específica para detectar hemoglobina humana con un punto de corte de 100 ng/ml (prueba positiva). Se realizó colonoscopia a los positivos. Se tomaron biopsias dirigidas de las lesiones premalignas/cáncer para análisis histopatológico. RESULTADOS: Se procesaron 751 FIT, de las cuales 51 (6.8%) fueron positivas, con una tasa de 15.9 lesiones premalignas por cada 1,000 sujetos evaluados, y 1.3 pacientes con CCR por cada 1,000 pacientes. CONCLUSIONES: Nuestro estudio concuerda con lo reportado en la literatura mundial, apoyando así la iniciativa de fomentar el establecimiento de un tamizaje formal y estandarizado dentro del sector de salud pública.

Screening for colorectal cancer in Uruguay with an immunochemical faecal occult blood test.

An observational prospective study was carried out in Uruguay to evaluate the feasibility of colorectal cancer screening using immunochemical faecal occult blood tests with no dietary restrictions in an average-risk population. An automated system was used for processing the samples with a cut-off haemoglobin level of 100 ng/ml. Of the 11,734 study participants who received an immunochemical test kit (OC-Hemodia), 10,573 (90.1%) returned samples for screening. The results of 1170 (11.1%) of the responders were positive. Subsequently, colonoscopy was performed on 879 (75.1%) of the participants with a positive test result and showed neoplasia in 330 participants. Fifty four had advanced cancer, 47 had early cancer, 131 had high-risk adenoma and 98 had low-risk adenoma. The detection rates and the positive predictive values were 0.95 and 8.6% for cancer, and 1.24 and 11.2% for high-risk adenoma, respectively. The high compliance and high detection rates for cancer and high-risk adenoma achieved in the colorectal cancer screening programme verifies the feasibility of an immunochemical faecal occult blood test in screening an average-risk population in Uruguay, a country with a small population, but with high morbidity and mortality rates for this disease.