Table 2.

Interpretive Criteria Applied to European and US Immunoblot Assays

Immunoblot	Criteria for a Positive Result
European IgM	≥1 of the following 5 bands must be present: VlsE, p39, p41 (strong intensity), OspC, DbpA (Osp17) [40]
European IgG	≥2 of the following 10 bands must be present: VlsE, p83/100, p58, p43, p39, p30, OspC, p21, Osp17, p14 [40]
US IgM	Conventional CDC criteria [15]: ≥2 of the following 3 bands must be present: 24 kDa (OspC), 39 kDa (BmpA), and 41 kDa (Fla)
	Hybrid IgG + VlsE criteria [28]: an IgM immunoblot is not used; the criteria rely solely on an IgG immunoblot that has been modified by the addition of rVlsE in a specified location.
US IgG	Conventional CDC criteria: ≥5 of the following 10 bands must be present: 18 kDa, 21 kDa (OspC), 28 kDa, 30 kDa, 39 kDa (BmpA), 41 kDa (Fla), 45 kDa, 58 kDa (not GroEL), 66 kDa, and 93 kDa [15]
	Hybrid IgG + VlsE criteria [28]: When early infection is suspected (EM, acute carditis, or acute LNB), the rVlsE band alone is scored, and the IgG immunoblot is considered positive if the rVlsE band is present. When late infection is suspected (LA or ACA), 11 bands on the IgG immunoblot are scored (the 10 bands included in the CDC IgG criteria listed above, plus the rVlsE band), and the immunoblot is considered positive if ≥5 of the 11 bands are present.

Abbreviations: ACA, acrodermatitis chronica atrophicans; CDC, Centers for Disease Control and Prevention; EM, erythema migrans; IgG, immunoglobulin G; IgM, immunoglobulin M; LA, Lyme arthritis; LNB, Lyme neuroborreliosis; rVlsE, recombinant VlsE; VlsE, Vmp-like sequence, expressed.