weil felix test

The Weil-Felix test detects typhus and specific rickettsial infections. Rickettsia is bacteria transmitted by ticks, fleas, lice and is the root of diseases in human beings. Rickettsial disease comprises of a set of diseases caused by the microorganisms like typhus, rickettsialpox, Boutonneuse fever, African tick bite fever, Rocky Mountain spotted fever, Australian Tick Typhus, Flinders Island Spotted Fever, Queensland tick typhus, Q fever, southern tick-associated rash illness (STARI), ehrlichiosis, and tularemia. The Weil Felix treatment would depend upon the nature and severity of the infection.

Diagnosis of Rickettsia is done with the help of an agglutination test, Weil Felix. Over the years it has been one of the most extensively used diagnostic procedure for detecting the infection. The basis of the Weil Felix test positive is to detect the anti-rickettsial antibodies present in the patient’s serum sample.

24 to 36 Hours

The Weil Felix test assesses the existence of rickettsia and varieties of rickettsial disease without specifications of species.

Some of the initial Weil Felix symptoms include: 

• Lack of appetite, Headache

• Backache, Fever

• Nausea

• Vomiting

• A severe headache

• Muscle pain

• Swelling of the parotid glands (behind the ear) Later signs and symptoms include:

• Abdominal pain

• Joint pain Skin Lesions

• Maculopapular rash

• Petechial rashes

Preparatory instructions before the test *include:

No Fasting Required. No other special preparations required.

Specimen type: Serum (Blood Sample),

Specimen collection procedure: Venipuncture - Collection of blood from a vein, usually from the arm.

The below table helps in understanding the Widal Weil Felix test interpretation. A titer of ≥1:320 is considered positive. The result is interpreted with respect to the most dilute tube in the series that shows positive signs.

The results of the Weil Felix test report depend on the agglutination reactions occurring based on the antigens common to both organisms. This reaction validates the presence and type f rickettsial infection.

To understand what is Weil Felix test it is necessary to have an idea of the basis on the which the test is conducted. An antigenic cross reaction activity between few serotypes of Proteus spp (non-motile) and Rickettsia spp is considered as the Weil Felix test principle. The serum sample of the patient is screened for this Weil Felix reaction. A cross-reaction between the OX antigens (OXK, OX 2 and OX 19) Proteus species strains along with the antibodies produced in acute rickettsial infections forms the basis for the Weil Felix test interpretation.

The procedure involves the collection of the blood sample from the patient in the tube or the vial and sending it for analysis. There are two methods of conducting the analysis at the lab.

Slide Method: A diminutive amount of the serum sample from the patient is placed on the slide after which the preferred antigen drop is added to it. The next step is to rotate the consequential postponement for a minute. If this results in visible agglutination, then a positive result is indicated.

Tube Method: As per the method twofold dilution of the serum sample is added to the tubes along with diluents, 0.25% of phenol saline. The tube’s final volume has to be made up to 1 ml. Antigen deferment is then further added and incubated for four to six hours at 50 to 55 °C. Positive results are indicated if there is granulation or visible flocculation.

There are no significant risks associated with the test. It is a simple blood test rarely a person might suffer from bruising or infection at the puncture site. The symptoms tend to gradually go away in some time.

Consuming alcohol before the test or taking any over the counter medication might alter your test results. It is always advisable to inform your doctor if you are on any prescribed medication.

The Weil Felix can serve as an initial screening test for rickettsia. Since the test does not provide any conclusive evidence, other tests like ELISA or immunofluorescence or Western blot are also prescribed by the doctor.

The Weil Felix test can be an important diagnostic tool in screening for typhus and various other rickettsial infections. The Weil Felix test positive treatment would depend on the type of infection.