What does the Borrelia burgdorferi Immunoglobulin G test measure?

Why is Borrelia burgdorferi Immunoglobulin G measured?

IgG serology supports the diagnosis of Lyme disease in patients with compatible clinical features and epidemiological exposure, particularly in late disseminated or chronic presentations where the rash is absent. Positive IgG alone does not confirm active infection and must be interpreted with clinical context, travel history, and other laboratory findings. Serological testing is insensitive in the first few weeks of illness.

Reference ranges

Standard reference

Negative <0.90; equivocal 0.90–1.10; positive >1.10 (laboratory-specific cut-offs).

Functional medicine optimal

Negative index value. Seropositivity reflects exposure; optimal clinical interpretation requires correlation with symptoms, tick exposure, and in many guidelines confirmation by Western blot.

Units

Index value, Arbitrary units/mL

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.