Every laboratory has a specific range that will be classified as normal for them. In general, however, the normal range for CgA is 1.9-15 ng/mL. Anything above this may be an indication of the presence of a tumor.
The good news is that when there is a positive result, about 80% of the tumors that are found tend to be benign.
Having high levels of chromogranin A is also a rather rare condition. The level of chromogranin A in the blood is normally low. A person with no signs or symptoms and a normal level of CgA is unlikely to have a neuroendocrine tumor.
However, the test is not perfect, and it is possible to have a neuroendocrine tumor even if the concentration of CgA is normal.
Not all patients with a neuroendocrine tumor have typical signs and symptoms. Some tumors do not produce the hormone associated with that tissue or only produce it intermittently.
The concentration of CgA is proportional to the tumor burden – the mass of the tumor. If concentrations of CgA are elevated prior to treatment and then fall, then treatment is likely to have been effective. If monitored levels begin to rise, then the person may have a recurrence of the tumor.