Can Blood Tests Detect Cancer? Types of Tests and Accuracy

📚 Quick Study Guide

• 🩸 Liquid Biopsy: Analysis of circulating tumor cells (CTCs) or circulating tumor DNA (ctDNA) in the blood.
• 🧬 Tumor Markers: Substances produced by cancer cells or other cells of the body in response to cancer. Examples include PSA (prostate-specific antigen), CA-125 (cancer antigen 125), and CEA (carcinoembryonic antigen).
• 🔬 Not Definitive: Blood tests are typically used as a screening tool or to monitor treatment, not to diagnose cancer definitively. Further imaging and biopsies are usually required.
• 📈 Sensitivity & Specificity: Sensitivity refers to the test's ability to correctly identify individuals *with* the disease (true positive rate). Specificity refers to the test's ability to correctly identify individuals *without* the disease (true negative rate).
• 🩺 Factors Affecting Accuracy: Stage of cancer, type of cancer, individual patient factors (e.g., other health conditions) all impact the accuracy of blood tests for cancer detection.
• 🧪 Types of Blood Tests: Includes complete blood count (CBC), blood protein testing (e.g., immunoglobulins), circulating tumor cell tests, and circulating tumor DNA tests.

Practice Quiz

1. Which of the following is a type of liquid biopsy?
   1. A. Complete Blood Count (CBC)
   2. B. Circulating Tumor DNA (ctDNA) analysis
   3. C. Basic Metabolic Panel (BMP)
   4. D. Lipid Panel
2. What is the main purpose of tumor marker blood tests?
   1. A. To definitively diagnose cancer
   2. B. To screen for cancer or monitor treatment progress
   3. C. To determine blood type
   4. D. To check for infections
3. Which of the following tumor markers is commonly associated with prostate cancer?
   1. A. CA-125
   2. B. CEA
   3. C. PSA
   4. D. AFP
4. What does 'sensitivity' in a cancer blood test refer to?
   1. A. The ability to correctly identify individuals without cancer
   2. B. The ability to correctly identify individuals with cancer
   3. C. The cost of the test
   4. D. The speed at which results are available
5. Which factor can significantly impact the accuracy of cancer blood tests?
   1. A. Patient's shoe size
   2. B. Type and stage of cancer
   3. C. Weather conditions
   4. D. Favorite color
6. A complete blood count (CBC) can provide information about which of the following?
   1. A. The presence of specific tumor markers
   2. B. The number and types of blood cells
   3. C. Circulating tumor DNA
   4. D. The patient's cholesterol levels
7. Why are blood tests not typically used to definitively diagnose cancer?
   1. A. They are too expensive.
   2. B. They often require confirmation with imaging and/or biopsy.
   3. C. They are only available in specialized hospitals.
   4. D. They are too painful for the patient.