What are the diagnostic tests and treatment options for typhoid fever?

Diagnostic Tests and Treatment for Typhoid Fever

Blood culture is the primary recommended test for diagnosing typhoid fever, with bone marrow culture being the gold standard when available, especially if antimicrobials have been administered. 1

Diagnostic Tests for Typhoid Fever

First-Line Diagnostic Tests

• Blood Culture:

  • Sensitivity: 40-80% 1
  • Collect 2-3 blood cultures (20mL each for adults) before antibiotics 2
  • Primary recommended test despite moderate sensitivity 1

• Bone Marrow Culture:

  • Gold standard with higher sensitivity than blood culture 1
  • Particularly valuable if antimicrobials have been administered 2
  • More invasive but more reliable 2

• Stool Culture:

  • Sensitivity: 35-65% 2, 1
  • Useful adjunct to blood culture 1

Additional Diagnostic Methods

• Culture-independent methods:

  • Panel-based multiplex molecular diagnostics from stool and blood specimens 2, 1
  • Should be performed when clinical suspicion exists 2

• PCR-based testing:

  • High sensitivity (86-100%) in research studies 3, 4
  • Particularly useful in culture-negative cases with clinical suspicion 4
  • Not yet widely available in all settings

• NOT Recommended:

  • Serologic tests (Widal test): Lacks sensitivity and specificity 2, 1
  • Poor performance characteristics with high false positive rates 3

Newer Rapid Tests

• Typhidot, Typhidot-M, TUBEX:
  • Show promise but with mixed results 2
  • TyphiDot and TUBEX demonstrated better sensitivity (79% and 78%) and specificity (89%) than Widal test in research studies 5
  • Most sensitive during the second week of illness 5

Treatment of Typhoid Fever

First-Line Treatment

• Ceftriaxone:
  • 2g IV every 24 hours for 10-14 days 1
  • First-line agent, especially for patients returning from Asia due to increasing fluoroquinolone resistance 1
  • All isolates reported to UK Health Protection Agency in 2006 were sensitive to ceftriaxone 2

Alternative Treatments

• Azithromycin:

  • Suitable oral alternative for uncomplicated disease 2
  • Use when fluoroquinolone resistance is confirmed 2, 1
  • Resistance is currently rare in many regions 2

• Fluoroquinolones (e.g., Ciprofloxacin):

  • Use only if confirmed sensitive to both ciprofloxacin and nalidixic acid 2, 1
  • More than 70% of S. typhi and S. paratyphi isolates imported into the UK are resistant to fluoroquinolones 2
  • When sensitive, they remain highly effective with cure rates >96% 2

Treatment Approach

1. Start empiric treatment with ceftriaxone if clinical suspicion is high and patient is unstable 2, 1
2. Adjust therapy based on culture and sensitivity results 6, 7
3. Continue treatment for 14 days to reduce risk of relapse 2
4. Consider adding steroids in severe cases 2

Important Clinical Considerations

Common Pitfalls to Avoid

• Relying solely on Widal test for diagnosis 1
• Failing to collect blood cultures before starting antibiotics 1
• Using fluoroquinolones empirically without considering regional resistance patterns 1
• Overlooking typhoid fever in patients with fever but without diarrhea 1

Prevention

• Vaccination for travelers to endemic areas:

  • Oral live-attenuated Ty21a vaccine (efficacy 50-70%) 2, 1
  • Parenteral Vi-polysaccharide vaccine 2, 1
  • Neither vaccine protects against S. paratyphi infection 2

• Hygiene measures:

  • Hand hygiene
  • Consumption of safe water and food
  • Proper cooking and refrigeration of food 1

Reporting Requirements

• Typhoid fever is a notifiable disease in most countries 2
• Report confirmed cases to appropriate health authorities for surveillance and outbreak control 2

By following this diagnostic and treatment algorithm, clinicians can effectively manage typhoid fever while minimizing complications and preventing antimicrobial resistance.