Many believe that a blood, urine, or stool test can immediately detect cancer. In reality, laboratory tests only provide clues — a diagnosis is made based on a comprehensive examination. An oncologist explains what the tests show and why good results do not guarantee the absence of disease.
A bad test result does not always mean the presence of cancer, and a good result does not completely rule it out. Tests help the doctor assess the state of the body and identify possible deviations, but they do not replace a comprehensive examination, which includes a physical exam, ultrasound, colonoscopy, mammography, and other screenings.
Complete Blood Count
Oncologists are interested in the following indicators: hemoglobin, erythrocytes, leukocytes, and platelets:
- Hemoglobin: a decrease may be associated with anemia, but can sometimes be observed in stomach, intestinal, female reproductive organ tumors, or myeloma.
- Leukocytes: increase in leukemia, blood tumors, and infections; decreased levels occur in bone marrow diseases and after chemotherapy.
- Platelets: an increase may occur in myeloproliferative diseases and some tumors; a decrease occurs in leukemias, lymphomas, and cancer treatment.
It is important to assess the dynamics of changes and their combination with other symptoms, as deviations may be caused by infections, liver, or kidney diseases.
Biochemical Blood Test
Helps assess the functioning of internal organs and the impact of tumors on metabolism:
- Liver indicators (AST, ALT, alkaline phosphatase, GGT, bilirubin): elevation occurs in liver damage, hepatitis, fatty liver disease, or medication use.
- LDH and alkaline phosphatase: increase in lymphomas, melanoma, lung tumors, bone tumors, and metastases.
- Calcium and electrolytes: in myeloma, bone damage, or some forms of lung cancer, calcium levels may rise.
General Urine Analysis
The analysis assesses kidney function and detects blood or inflammation:
- Blood in urine: may be the first sign of kidney or bladder tumors, although it is more often associated with stones or infection.
- Protein and other changes: possible in myeloma and blood tumors; require further examinations.
Fecal Occult Blood Test
Used in colorectal cancer screening, but does not replace colonoscopy. Detection of blood requires further diagnostics, as bleeding may be related to hemorrhoids, fissures, or polyps.
Conclusion
Normal test results do not exclude cancer, and changes in them do not always indicate oncology. Regular examinations, screenings, and careful attention to health remain key to early disease detection.
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