Regarding the diagnosis and management of enteric fever caused by Salmonella typhi, all of the following statements are correct EXCEPT:

Explanation

## Diagnostic Pitfalls and Management Principles in Enteric Fever ### The Widal Test Trap **Key Point:** Widal test is NOT diagnostic of acute enteric fever based on single titre values. A RISING titre (4-fold increase between acute and convalescent sera) is required for diagnosis, not a single high titre. Single high titres can reflect previous infection, vaccination, or endemic background seropositivity. **Warning:** Many students incorrectly believe that O ≥1:160 and H ≥1:320 are diagnostic thresholds. This is a common NEET PG trap. The test is unreliable in endemic areas and has poor specificity. ### Correct Diagnostic and Management Statements | Statement | Validity | |-----------|----------| | Blood culture = gold standard, highest sensitivity week 1 | ✓ True — 80–90% sensitivity in first week | | Widal single titre ≥1:160 O, ≥1:320 H = diagnostic | ✗ False — requires paired/rising titre | | Fluoroquinolones first-line for uncomplicated, low-resistance areas | ✓ True — ciprofloxacin/ofloxacin standard | | Bone marrow culture > blood culture sensitivity, reserved for culture-negative | ✓ True — 80–90% sensitivity even after antibiotics | ### Diagnostic Algorithm ```mermaid flowchart TD A[Suspected enteric fever]:::outcome --> B{Blood culture positive?}:::decision B -->|Yes| C[Diagnosis confirmed]:::action B -->|No| D{Widal test}:::decision D -->|Rising titre| E[Likely enteric fever]:::outcome D -->|Single high titre| F[Non-diagnostic]:::outcome F --> G{Still suspect enteric fever?}:::decision G -->|Yes| H[Bone marrow culture]:::action G -->|No| I[Consider alternative diagnosis]:::action ``` **Clinical Pearl:** In endemic areas like India, Widal test background seropositivity is high (20–40% of healthy individuals have O titre ≥1:80). Paired sera showing 4-fold rise is far more reliable than a single high titre. **High-Yield:** Blood culture remains the gold standard. If negative and clinical suspicion is high, bone marrow culture (not repeat blood cultures) is the next step. Widal is supportive only when paired titres show rise. [cite:Harrison 21e Ch 159]