CEACAM5 and hepatitis A virus infection: Other factors include the nonspecificity of CEA and CA 19.9 toward a particular histological type or origin of the carcinoma, false-positive results from the elevation of CEA levels due to benign conditions (e.g. hepatitis, pancreatitis, obstructive pulmonary disease, and inflammatory bowel disease), and analytical variables such as variations in sampling and storage methods, patients’ condition, and stability of the biomarkers [62,63].