Lyme disease is caused by Borrelia burgdorferi (sensu lato). The two-tier serological testing algorithm used for diagnosis consists of:
- A IgM ELISA followed by confirmatory dark-field microscopy of blood
- B PCR of blood in all stages followed by ELISA confirmation
- C Screening ELISA (whole cell sonicate) followed by confirmatory Western blot (IgM and IgG criteria separately) ✓
- D VDRL followed by TPHA (same as syphilis testing)
Correct answer: C. Screening ELISA (whole cell sonicate) followed by confirmatory Western blot (IgM and IgG criteria separately)
Explanation
CDC two-tier Lyme serology: Step 1 — enzyme immunoassay (EIA) or IFA using whole-cell sonicate of B. burgdorferi; if positive or equivocal, Step 2 — Western immunoblot with separate IgM criteria (2 of 3 bands: 23, 39, 41 kDa) and IgG criteria (5 of 10 specific bands). Both steps must be positive for seropositivity. PCR is useful for synovial fluid in Lyme arthritis but poorly sensitive for blood. Dark-field microscopy is for Leptospira/Treponema, not Borrelia in blood. VDRL/TPHA is for syphilis (Treponema pallidum).
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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