Widal test is performed in a patient with suspected enteric fever. The O antigen titre is 1:160 and H antigen titre is 1:80. A titre of ≥1:160 for O antigen is considered significant. The most appropriate interpretation is:
- A Suggestive but not specific; blood culture is the gold standard for diagnosis ✓
- B Highly specific for active Salmonella Typhi infection; no further workup needed
- C H antigen rising titre is more diagnostically specific than O antigen titre
- D A single titre is diagnostic in non-endemic areas regardless of clinical context
Correct answer: A. Suggestive but not specific; blood culture is the gold standard for diagnosis
Explanation
Widal test has major limitations: cross-reactions with other Enterobacteriaceae, prior typhoid vaccination, and endemic background titres make a single titre unreliable. Blood culture remains the gold standard (70–80% sensitivity in first week), and bone marrow culture has the highest sensitivity (~95%) even after antibiotic use. A fourfold rise in O antigen titre between acute and convalescent sera is more meaningful. Modern diagnostics include Typhidot (IgM anti-OMP), Tubex TF, and typhoid-specific PCR.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.