What is the interpretation of a WIDAL (Widal test) titre of 1:80 or higher in a patient presenting with symptoms of typhoid fever?

Widal Test Interpretation

The Widal test should NOT be used as a standalone diagnostic tool for typhoid fever due to its poor positive predictive value (5.7%) and low specificity (68.44%), and blood culture remains the gold standard for diagnosis. 1, 2

Why the Widal Test is Unreliable

The CDC and current guidelines explicitly recommend against using the Widal test alone for diagnosis of enteric fever due to poor performance characteristics. 3, 1 The critical problem is that while a titre of 1:80 or higher may suggest recent infection, the test generates far too many false positives to be clinically useful:

• Positive predictive value is only 5.7%, meaning that among patients with a positive Widal test, fewer than 6% actually have typhoid fever 2
• Specificity is only 68.44%, resulting in approximately one-third of healthy individuals testing falsely positive 2
• In endemic areas, 13.8-18.5% of healthy individuals have baseline antibody titres without active disease 4

What a Titre of 1:80 or Higher Actually Means

When interpreting specific titre levels in the context of clinical symptoms:

• Anti-TO (O antigen) titre ≥1:80 has 90% sensitivity and 87.3% specificity, with a positive predictive value of only 52.2% 4
• Anti-TH (H antigen) titre ≥1:80 has 90% sensitivity and 88.5% specificity, with a positive predictive value of 54.6% 4
• Some studies suggest higher cut-offs (≥1:160 for H, ≥1:80 for O) may be more appropriate, but this still doesn't overcome the fundamental limitations 2, 5
• The negative predictive value is excellent (98.3%), meaning a negative Widal test is more useful for ruling OUT typhoid than a positive test is for ruling it IN 4, 2

The Correct Diagnostic Approach

Always obtain blood cultures before starting antibiotics whenever possible, as they have 40-80% sensitivity and are the gold standard for diagnosis. 6, 1 Blood cultures have the highest yield in the first week of symptoms. 3, 6

If you encounter a patient with:

• Sustained fever, headache, malaise, and gastrointestinal symptoms 3
• Travel history to endemic areas (South/Southeast Asia) 3
• A Widal titre of 1:80 or higher

Your clinical decision should be based on the clinical presentation and epidemiological risk factors, NOT the Widal titre alone. 1, 5

Practical Management Algorithm

1. Collect blood cultures immediately before antibiotics if the patient is stable 6, 1

2. If clinically unstable or septic, start empiric treatment after culture collection:

   • Azithromycin 500 mg once daily for 7 days (first-line for adults) 1
   • Ceftriaxone 1-2g IV daily for 5-7 days for severe cases 1
   • Never use ciprofloxacin empirically for cases from South/Southeast Asia due to >70% resistance 1

3. Continue full treatment course (7-14 days) even if fever resolves early to prevent relapse (10-15% if inadequately treated) 1

Critical Pitfalls to Avoid

• Never diagnose typhoid based solely on Widal test results - the high false-positive rate leads to massive overdiagnosis and inappropriate antibiotic use 1, 7
• Never withhold treatment waiting for culture results if the patient has sepsis features or severe illness 3, 1
• Never use empiric fluoroquinolones for patients from Asia where resistance approaches 96% 1
• Studies show that Widal slide tests lead to overtreatment, with 76.1% of patients receiving unnecessary ciprofloxacin 7

The Bottom Line

A Widal titre of 1:80 or higher in isolation is not diagnostic and should be interpreted only in conjunction with clinical features and travel history. 8, 5 The test's poor positive predictive value means most positive results are false positives, leading to overdiagnosis and inappropriate antibiotic use. 1, 2, 7