Stevens Immunology-Serology Practice Test

Tumor markers are not specific to cancer; they can go up in a range of non-cancer conditions. For screening the general population, you need a test with high specificity, because the population prevalence of cancer is low. If a marker can be elevated in benign or inflammatory states, many healthy people would test positive, leading to false positives and unnecessary follow-up procedures, anxiety, and potential harms, while still missing cancers in those who don’t have a pronounced marker elevation. That’s why these markers are not suitable for population screening.

For context, PSA can be raised by benign prostatic hyperplasia or prostatitis; CA-125 can be elevated with endometriosis, fibroids, or pregnancy; CEA can be higher in smokers or inflammatory conditions; CA 19-9 can rise with pancreatitis or biliary obstruction. The key issue is lack of cancer-specificity, not cost, the absolute level rise, or differences among ethnic groups.