MLT GlobeChemistry: Tumor markers & iron studies – page 2
59 Chemistry MCQs on Tumor markers & iron studies with answers and explanations.
Very high serum hCG in a non-pregnant woman is a tumor marker for:
hCG is produced by trophoblastic tissue, so it is the marker for gestational trophoblastic disease, including choriocarcinoma and hydatidiform mole.
Besides yolk sac tumor, markedly raised serum AFP is characteristic of:
AFP is produced by fetal liver and yolk sac, and re-expressed by hepatocellular carcinoma. Choriocarcinoma secretes hCG, and prostatic carcinoma PSA.
A man has total PSA of 6 ng/mL (6 µg/L). A LOW percentage of free PSA suggests:
In prostate cancer, more PSA circulates bound to antiproteases, so the free fraction is lower. A high percent free PSA favours benign enlargement.
CA-125 is used mainly to monitor ovarian epithelial cancer. Which benign condition can also raise it?
CA-125 can rise in endometriosis, menstruation, pregnancy and peritoneal inflammation. This limits its use for screening in the general population.
After complete removal of an AFP-producing tumor, AFP (half-life about 5 days) falls from 800 ng/mL to 400 ng/mL in 30 days. This most suggests:
With a half-life of about 5 days, AFP should fall by far more than half in 30 days (about 6 half-lives). A slow fall suggests continued production by residual tumor.
A patient has flushing and diarrhea. A 24-hour urine 5-HIAA is raised. This supports:
5-HIAA is the main metabolite of serotonin, which carcinoid tumors make in excess. Foods such as bananas and walnuts can falsely raise it.
A patient with rheumatoid arthritis has anemia. Which iron profile is most typical?
Inflammation raises hepcidin, trapping iron in stores: serum iron falls, TIBC is low or normal, and ferritin is normal or high. High TIBC with low ferritin fits iron deficiency.
A 45-year-old man has fatigue and bronze skin. Fasting transferrin saturation is 78% and ferritin is very high. The next test is:
High transferrin saturation with high ferritin suggests hereditary hemochromatosis, most often HFE C282Y homozygosity. Genetic testing is the usual next step.
Serum iron is 60 µg/dL (10.7 µmol/L) and TIBC is 400 µg/dL (71.6 µmol/L). The transferrin saturation is:
Transferrin saturation = serum iron ÷ TIBC × 100 = 60 ÷ 400 × 100 = 15%. A value below about 16–20% supports iron-deficient erythropoiesis.
Why are serum iron samples ideally collected in the morning after fasting?
Serum iron is usually highest in the morning and varies widely during the day; recent intake or supplements also raise it. Standard timing makes results easier to interpret.
A patient with active infection has serum ferritin of 80 ng/mL (80 µg/L), low serum iron and absent marrow iron stores. Ferritin is misleading because it:
Inflammation raises ferritin independent of iron stores, so a 'normal' value can hide iron deficiency. Higher cut-offs or other markers are used in inflammation.
Hepcidin controls body iron by:
Hepcidin binds ferroportin and causes its breakdown, reducing iron absorption from the gut and release from macrophages. Raised hepcidin in inflammation explains the low serum iron of chronic disease.
Which condition is most likely to cause a marked but temporary rise in serum PSA?
Inflammation disrupts prostate tissue so more PSA leaks into blood; PSA should be re-tested after the infection has settled. 5-alpha-reductase inhibitors lower PSA.
In the International Staging System for multiple myeloma, which two serum tests are used together?
ISS stage is based on serum beta-2 microglobulin (reflecting tumor burden and kidney function) and albumin; the revised ISS adds LDH and cytogenetics. Calcium and creatinine assess organ damage.
A patient with episodic headache, sweating and palpitations has very high blood pressure. The preferred first biochemical test is:
Plasma free (or urine fractionated) metanephrines are the most sensitive screening tests for pheochromocytoma and paraganglioma. Urine 5-HIAA is used for carcinoid tumors.
Which marker is combined with CA-125 in the ROMA algorithm to assess the risk of ovarian malignancy in a pelvic mass?
ROMA combines CA-125 and HE4 with menopausal status. HE4 is less often raised by benign conditions such as endometriosis, improving specificity over CA-125 alone.
Why is a hemolyzed sample unsuitable for neuron-specific enolase (NSE) measurement in small cell lung cancer?
NSE is present in erythrocytes and platelets, so hemolysis or delayed separation releases it and falsely raises results. Samples should be separated promptly and not hemolyzed.
A patient with a gallstone blocking the common bile duct and cholangitis has a CA 19-9 of 900 U/mL. After the stone is removed, CA 19-9 becomes normal. The raised value was due to:
CA 19-9 is cleared through bile, and biliary obstruction or inflammation can raise it greatly without cancer. Normalization after relieving obstruction supports a benign cause.
A patient with thalassemia receives regular transfusions. Roughly how much iron does each unit of red cells add to body stores?
Each unit of red cells contains about 200–250 mg of iron, and the body has no active way to excrete it. Repeated transfusion therefore leads to iron overload needing chelation.
A patient took an oral iron tablet 2 hours before a blood sample for iron studies. What is the expected effect?
Absorbed iron raises serum iron and transferrin saturation for several hours. Iron supplements should be stopped at least 24 hours before testing. Ferritin does not change rapidly.