Vibrant uses a high-sensitivity peptide-based microarray to detect antibodies against specific peptide epitopes derived from tickborne pathogens. These tests provide quantitative values that reflect relative antibody binding activity, not just binary presence/absence.
Because of this sensitivity and the nature of peptide-antibody binding:
- There is often a small amount of non-specific background binding, even in healthy individuals.
- Low-level signals can occur due to cross-reactivity with similar antigens from unrelated exposures.
- The test reports arbitrary units or relative signal intensities, and the lab establishes a cutoff to determine what’s considered “in control”, “moderate” or “risk”
A non-zero IgM or IgG/IgA reading that is still below the positivity threshold does not confirm prior exposure. Instead, it may reflect:
- Low-level cross-reactivity
- Immune system priming from unrelated antigens
- Baseline immune surveillance
- Past minor or non-pathogenic exposure that didn’t lead to illness.
- It is unlikely that a person will have zero detectable IgA or IgG antibodies to tickborne antigens, especially in areas where tickborne diseases are endemic. Individuals are frequently exposed to tick bites. Minor exposures to pathogens with longer transmission windows can still elicit immune responses, without infection, particularly for pathogens with longer transmission windows based on duration of tick attachment.
- The 0–10 unit range is defined as “negative” — meaning typical for healthy individuals, not “zero antibodies”. The way I see it, zero is not used as the standard for “unexposed.” The cutoff (10 units) is based on what’s common in healthy individuals, not on absolute absence.
In contrast, significant elevations, especially across multiple bands or in clinically relevant patterns, are more suggestive of current or past infection. Interpretation should always consider:
- Clinical presentation and symptoms
- Timeline of illness
- Coinfections and immune status
The lack of zero values does not mean the patient was exposed to every pathogen or band. Instead, these values reflect the dynamic range of immune recognition.