Widal test is used for serological diagnosis of typhoid fever. A patient in an endemic area shows Widal titres: TO = 1:160, TH = 1:160. In the absence of prior vaccination or previous illness, which interpretation is MOST appropriate?

• A Definitive diagnosis of typhoid — no further testing needed
• B Titres of 1:160 are non-significant in all populations
• C TH titre is more important than TO for active disease; TH 1:160 alone confirms typhoid
• D Significant titres suggestive of typhoid in this endemic setting; however, the Widal test has poor specificity and should be supplemented with blood culture which remains the gold standard ✓

Explanation

Widal test interpretation must account for baseline titres in endemic populations; a TO titre ≥1:80 and TH titre ≥1:160 is conventionally considered significant in India (though lab and regional baselines vary). However, the Widal test has poor specificity (false positives from non-typhoidal Salmonella, malaria, viral hepatitis, endocarditis) and modest sensitivity (60–70%). Blood culture (yield ~80% in first week) remains the gold standard. A four-fold rise in titre in paired sera (collected 7–10 days apart) is more diagnostically reliable than a single sample.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.