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How to read your Western Blot Test Results

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How To Read Western Blot Test Results

The Western Blot Test does not actually test for the presence of Lyme disease. It tests indirectly by looking for antibodies made by your immune system agains Lyme disease bacteria, spirochetes, which causes Lyme disease.

Western Blot Bands description:

Please note:

Cross-reactive means it could indicate other spirochetes.

Specific means it only happnes when Lyme disease is present.

Borellia or Bb is Lyme disease.


18 p18 flagellin fragment
20 cross-reactive for Borrellia
21 unknown
22 specific for Bb, probably really the 23/25 band
23-25 outer surface protein C (OspC), specific for Bb
28 outer surface protein D (OspD); Oms28; specific for Bb
30 OspA substrate binding protein; common in European and one California strain
31 outer surface protein A (OspA), specific for Bb
34 outer surface protein B (OspB); specific for Bb
35 specific for Bb
37 specific for Bb
38 cross-reactive for Bb
39 is a major protein of Bb flagellin; specific for Bb
41 flagellin protein of all spirochetes; this is usually the first to appear after a Bb infection
45 cross-reactive for all Borellia (sometimes people with Lyme who have this band positive also have the co-infection Ehrlichiosis)
50 cross-reactive for all Borrellia
55 cross-reactive for all Borrellia
57 cross-reactive for all Borrellia
58 unknown but may be a heat-shock Bb protein
60 cross reactive for all Borrellia
66 cross-reactive for all Borrelia, common in all bacteria
83 specific antigen for the Lyme bacterium, probably a cytoplasmic membrane
93 unknown, probably the same protein in band 83, just migrates differently in some patients

The BOLDED bands above are very specific for Lyme disease.

On your Western Blot test you will also see references to IgG and IgM.

If you have a positive IgM, it may mean that you just became infected with Lyme disease.

If you have a positive IgG, it may mean that you have an establised, chrinic infection.

The CDC requires 5 out of 10 bands for a positive test. However, some bands on the Western blot are more significiant, therefore, your doctor may decide that you have Lyme disease even if your Western blot is not CDC positive. The current CDC criteria, which is used by the IDSA and health insurance companies, for a positive Western Blot are as follows:

For IgM, 2 of the following three bands have to be positive: OspC (22-25), 39 and 41

For IgG, 5 of the following ten bands have to be positive: 18, OspC (22-25), 28, 30, 39, 41, 45, 58, 66 and 93.

The criteria used by IGeneX considers a Western Blot (IgM or IgG) to be posi