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Diagnosis and explain
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"Weil-Felix Test" AND rickettsial
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CDC rickettsial diseases Weil-Felix test not recommended diagnosis
Most likely interpretation: suspected scrub typhus (a rickettsial infection).
Your Weil-Felix report shows:
| Antigen | Titer | Usual association |
|---|---|---|
| OX-K | 1:160 | Often associated with scrub typhus |
| OX-2 | 1:80 | Can occur with spotted-fever group rickettsioses |
| OX-19 | 1:80 | Can occur with typhus-group/spotted-fever rickettsioses |
The OX-K titer of 1:160 is the main finding. In a person with fever, headache, body aches, rash, swollen lymph nodes, or a dark scab-like bite mark called an eschar, it can support a clinical suspicion of scrub typhus.
However, this result alone cannot confirm the diagnosis. Weil-Felix is an older screening test with limited sensitivity and specificity. The CDC scrub-typhus guidance states that OX-K Weil-Felix testing is not recommended as a definitive diagnostic assay. False positives can occur, and a single titer should be interpreted alongside symptoms, examination, timing of illness, and local disease patterns.
What to do
- See the treating physician promptly, especially if fever is ongoing.
- Ask whether confirmatory testing is available, such as scrub-typhus IgM/IgG ELISA or IFA, and sometimes PCR early in illness.
- If the clinician strongly suspects rickettsial disease, treatment is often started based on clinical assessment rather than waiting for delayed confirmation.
- Seek urgent care for confusion, severe breathlessness, persistent vomiting, low urine output, jaundice, bleeding, very low blood pressure, or worsening weakness.
This report is best described as Weil-Felix positive with an OX-K-predominant pattern, suggestive but not diagnostic of scrub typhus.
Normal range of titre
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Weil Felix test titre significant cutoff 1:80 1:160 scrub typhus India guideline
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"Weil-Felix Test" AND "scrub typhus"
For the Weil-Felix test, there is no single universal “normal” value because background antibody levels vary by region and laboratory.
A practical interpretation commonly used in India:
- Below 1:80: usually considered non-significant or negative
- 1:80: may indicate a possible rickettsial infection, but needs symptoms and clinical correlation
- 1:160 or higher: more suggestive/significant, especially with fever and compatible symptoms
- A four-fold rise in titre on a repeat sample after 1-2 weeks is stronger evidence of a recent infection
For your report:
- OX-2: 1:80
- OX-19: 1:80
- OX-K: 1:160
So, OX-K 1:160 is above the usual screening threshold and is suggestive of scrub typhus in the appropriate clinical setting. It is not, by itself, a confirmed diagnosis because Weil-Felix can be falsely positive or negative.
The DHR-ICMR rickettsial-disease guideline treats a titre of 1:80 as possible infection, while noting that each region should ideally establish its own baseline titres. Confirmatory scrub typhus IgM ELISA/IFA is more reliable.
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