Under Estimation and Over Estimation in Gastric Cancer Incidence Registry in Khorasan Provinces

Gastric cancer is a disease which the cells forming the inner lining of the stomach start todivide uncontrollably, forming a mass called a tumor. Patients with gastric cancer from lowfacilityprovinces like North and South Khorasans may diagnose and registered in fullfeaturedprovinces like Razavi-Khorasan; this causes misclassification error. The presence ofthis error makes the registry systems inaccurate and unreliable for estimating the burden ofcancer and policy making. Two approaches are recommended for reducing the effects ofmisclassification; the first is using a small validation sample and the second is a Bayesiananalysis which provides subjective prior information for the subset of the parameters tocorrect the statistics. Data for this study extracted from Iranian annual of national cancerregistration report in 2008. The age standardized rate due to gastric cancer [ICD-10; C16]were expressed as rate per/100,000 population for male and female of North, South andRazavi Khorasans. To correct the misclassification effect, a Bayesian approach was usedwith Poisson count regression and beta prior. The reported expected coverage of cancerincidence for Razavi-Khorasan was 155.5% and exceeds than what expected, whereas theNorth and South Khorasans have just observed respectively 34.8% and 41.4% of theirexpected coverage. The results of the Bayesian analysis indicated that there was about 34%misclassification in gastric cancer incidence registry from North and South Khorasans inRazavi-Khorasan. In planning for resource allocation, authorities should consider that, lowincidence of gastric cancer in North and South Khorasans, may be the effect ofmisclassification and it is needed to allocate them more health facilities and improve theiraddress registration accuracy using National ID, electric bill, etc.

کلیدواژه ها:

Gastric Cancer ، Misclassification Error ، Bayesian Method ، Incidence ، Cancer Registry