The incidence rate of familial adenomatous polyposis

Abstract

Based on the Danish Polyposis Register epidemiological calculations on familial adenomatous polyposis (FAP) were carried out. The mean annual incidence was 1.85x10^-6 during the years 1971–1992, and the prevalence increasing to about 32x10^-6 at the end of 1992. FAP patients constituted a decreased percentage of all Danish patients with colorectal cancer (0.07% in 1980–1992). The completeness of registration was 97% in 1983–1992. The results are similar to Finnish estimates based on the same direct method of calculation, and as both series are based on almost complete national polyposis registration in well-registered populations we regard our results to be close to the true incidence rate.

Résumé

En se basant sur le registre danois des polyposes, des calculs épidémiologiques ont été réalisés sur la polypose familiale multiple. L'incidence annuelle moyenne est de 1.85x10^-6 au cours des années 1971 à 1992 et la prévalence augmente à environ 32x10^-6 à la fin de 1992. Les patients porterus d'une polypose familiale constituent un pourcentage en diminution de tous les patients porteurs d'un cancer colo-rectal (0.07% entre 1980 et 1992). L'exactitude du registre était de 97% entre 1983 et 1992. Les résultats sont similaries aux estimations finlandaises basées sur une même méthode de calcul; et étant donné que les deux séries témoignent d'un enregistrement pratiquement complet des polyposes à l'échelon national dans une population correctement enregistrée, nos résultats semblent refléter l'incidence réelle de l'affection. and increasing bias due to the significant improval of the prognosis of familial adenomatous polyposis during the last decades. Moreover, most studies are not based on epidemiologically valid patient series without selection bias. Recent calculations of the incidence rate with a direct method have been published on the basis of the national Danish and Finnish polyposis series, showing an annual incidence rate of 1.3–1.6x10^-6 in the early 1980's [5, 6].

The aim of the present study was to reevaluate the occurrence of the disease about 25 years after the establishment of the Danish Polyposis Register by presenting estimates on the incidence rate, the point prevalence rate, and the completeness of registration.