What Is Biomarker Testing?
Biomarker testing measures selected blood, urine, or other indicators to answer a clinical question. Useful testing links each result to pretest probability, standardized collection, interpretation, and an action plan.
Overview
Biomarker testing measures a biological signal, but a measurable value is not automatically useful. Good testing starts with the question: screening, diagnosis, medication safety, risk estimation, or treatment monitoring.
More tests create more abnormal flags
Reference intervals commonly include about 95% of a defined healthy population. If many independent tests are ordered, at least one out-of-range result becomes likely by chance. Results also vary with fasting, time, hydration, exercise, illness, menstrual status, supplements, medications, assay, and laboratory.
Common high-value domains
Depending on age and risk, testing may include lipids or apolipoprotein B, glucose or A1c, kidney and liver measures, blood count, thyroid testing when indicated, and disease-specific screening. Specialized tests should add decision value beyond history, examination, and established measures.
Reference is not automatically optimal
A laboratory interval describes distribution, while a guideline target links a value to outcomes and treatment evidence. Clinics should not invent “optimal” ranges that convert healthy variation into disease.
Build a closed loop
Every order needs a reason, preparation instructions, named reviewer, plan for critical values, interpretation with absolute risk, confirmatory testing when appropriate, and a schedule based on whether results change care.
Benefits
Can identify established disease or treatment risk when appropriately selected
Supports cardiovascular and metabolic risk estimation
Monitors medication effectiveness and safety
Creates measurable baselines under standardized conditions
Can reduce uncertainty when tied to a clear decision
The Procedure
1
Define the decision
2
Standardize collection
3
Interpret in context
4
Close the loop
Preparation
Follow test-specific fasting and timing instructions; avoid unusually strenuous exercise or supplements only when directed. Bring medications, supplements, prior results, family history, and the clinical question.
Recovery & Aftercare
Usually limited to brief blood-draw soreness or bruising. Seek care for persistent bleeding, major swelling, fainting, or signs of infection.
Risks & Considerations
False positives or negatives, incidental abnormalities, anxiety, unnecessary imaging or procedures, overdiagnosis, inappropriate supplements or medications, cost, privacy concerns, and anemia from excessive repeated blood draws.
Frequently Asked Questions
References
[1]
FDA: Laboratory Developed Tests.
https://www.fda.gov/medical-devices/in-vitro-diagnostics/laboratory-developed-tests[2]
CDC: Clinical Laboratory Systems.
https://www.cdc.gov/clinical-laboratory-systems/php/about/index.html
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