Proteomics test: what a protein biomarker test measures, and what it cannot

A biomarker test measures something in the body that indicates what the body is doing. The FDA-NIH Biomarker Working Group defines a biomarker as a defined characteristic measured as an indicator of normal biological processes, pathogenic processes or responses to an exposure or intervention, and it names molecular, histologic, radiographic and physiologic biomarkers (BEST glossary). A blood protein such as CRP is a molecular biomarker.

The same glossary draws a line that matters to anyone with persistent symptoms: a biomarker is no assessment of how a person feels, functions or survives (BEST glossary). A protein level and a symptom answer different questions. A good record holds both.

Biomarkers do different jobs. The BEST glossary describes a monitoring biomarker as one measured at intervals to assess status or track change (BEST, monitoring biomarker). That is the job most relevant to someone tracking a long illness.

Many proteins travel in the blood as signals or by-products. Immune cells release cytokines, the signalling proteins that coordinate inflammation, and IL-6 prompts the liver to make CRP (Hunter and Jones, 2015). Stressed nerve cells release neurofilament light chain, which research uses as a blood marker of nervous system involvement (Molecular Psychiatry, 2024).

Each protein reflects one part of a system, and systems interact. A panel that reads many proteins from the same sample keeps the readings comparable and lets patterns show, which is why immune research profiles many measures at once. In a 2023 Nature study, that approach separated people with long COVID from people who had recovered at the group level (Klein et al., 2023). Our explainer on what proteomics testing is goes further into the method.

Standard panels answer specific clinical questions with a small set of measures. The CDC's list of basic screening tests for ME/CFS is typical: a complete blood count, electrolytes, glucose, kidney and liver tests, thyroid tests, ESR, CRP and urinalysis (CDC). Most of these count cells, measure salts and enzymes, or read one protein at a time.

Those tests find anemia, thyroid disease, diabetes and kidney or liver problems, and they matter. They leave most signalling proteins unmeasured. The CDC notes that routine blood tests may be normal in someone with long COVID (CDC), and a large study found common lab tests unreliable for diagnosing it (CU Anschutz). The guide to inflammation markers covers the difference between CRP and a cytokine panel.

Biomarker tests differ in what they measure and in how far anyone has validated their results. Six points help you and your doctor compare them:

• The protein list. A named list, or at least the domains and example markers, shows whether the test covers your questions.
• The reference. A result means little until you know the comparison group, such as healthy adults of a similar age.
• Regulatory status. Some tests are FDA-cleared for a diagnostic use; others are research-grade tests offered for research and informational purposes. The label shapes how a doctor can use the result.
• Diagnostic claims. A research-grade panel that says it diagnoses a condition is claiming more than the evidence supports.
• Repeatability. Tracking change needs the same method each time.
• The reader. Your own doctor should be part of reading the result.

A proteomics test can show where many proteins sit against a healthy reference at one moment, and a series of tests can show which way they move. Sensitive assays read signalling proteins at low concentrations: single-molecule immunoassays have measured IL-6, TNF-α, IL-10 and IL-1β at concentrations as low as 0.01 to 0.03 pg/mL (2023 assay study). Broad platforms extend that to thousands of targets (Nature Communications, 2021).

A proteomics test cannot diagnose a condition, and research differences between groups do not translate into a verdict about one person. A protein level cannot measure how you feel (BEST glossary). A result outside the healthy range is a question for your doctor, read in the light of your history and other results. A panel cannot choose a treatment.

Mune Mirror™ is currently in development, and the performance characteristics of this test have not yet been established. It is investigational. It does not diagnose, detect, screen for, treat, cure or prevent any disease. Results are for research and informational purposes, to discuss with your own doctor.

The guide to unwellness testing explains where this measurement fits, and the list of what Mune Mirror™ measures shows its eight domains.

Mune Mirror™ is a proteomics test focused on the immune system: more than 1,000 immune and inflammation proteins from an at-home sample, each benchmarked against a healthy reference and repeated over time. It gives you and your doctor a broad, measured record. It does not diagnose any condition.

What is a proteomics test?

A proteomics test measures many proteins in one sample, from dozens to thousands, using methods such as affinity-based proteomics. It shows where each protein sits and, repeated over time, how the pattern changes. It does not diagnose a condition on its own.

What is a biomarker test?

A biomarker test measures a characteristic that indicates normal biology, a disease process or a response to an exposure or treatment, as defined by the FDA-NIH BEST glossary. Blood proteins such as CRP or IL-6 are molecular biomarkers. A biomarker does not measure how a person feels or functions.

Can a proteomics test diagnose disease?

No. A proteomics test measures proteins and compares them with a reference. Differences found between groups in research do not diagnose one person. Research-grade panels such as Mune Mirror™ are investigational and for research and informational use.

How is a proteomics test different from a standard blood test?

A standard blood test answers specific clinical questions with a small set of measures, such as a blood count or a thyroid test. A proteomics test reads hundreds or thousands of proteins from one sample, which shows patterns a single test cannot.

Why measure proteins more than once?

One measurement shows one moment. The BEST glossary describes a monitoring biomarker as one measured at intervals to assess status or track change, and a series of results shows direction over time.