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XPECT Rotavirus Test

Code: R24655

The Xpect™ Rotavirus test is a rapid, membrane-based, immunogold assay for the qualitative detection of rotavirus antigens in human faecal specimens. The test is intended for use as an aid in the diagnosis of acute gastroenteritis caused by rotavirus infections. The Xpect Rotavirus Control Kit contains a positive and negative liquid control for use with the Xpect Rotavirus Kit.

Additional information can be obtained by downloading the Xpect Rotavirus IFU (427KB) in PDF format.

Background
Rotavirus is the most frequent cause of severe acute gastroenteritis and diarrhoea among infants and children worldwide, though humans of all ages are susceptible to infection.  Rotavirus infection can be asymptomatic or result in mild to severe illness.  Children 6 months to 2 years of age, premature infants, the elderly, and the immunocompromised are particularly prone to more severe symptoms caused by infection with group A rotavirus.  The incubation period ranges from 1-3 days.  Symptoms often start with vomiting followed by 3-9 days of non-bloody diarrhoea.  Some children experience seizures with fever or chronic malabsorption and require a longer period of recovery or a more complicated evaluation.  Recovery is usually complete.  Repeated symptomatic rotaviral infections are common, but re-infections are typically less severe than first infections.

Six serological groups of Rotavirus have been identified. Groups A, B, and C infect humans, with group A being the most common and widespread. Group A Rotavirus is endemic worldwide. 

Each year, approximately 125 million cases of rotaviral gastroenteritis occur worldwide, resulting in up to 600,000 deaths, typically due to severe dehydration and electrolyte loss in infants and young children. In countries with a temperate climate, the disease has a winter seasonal pattern. Transmission of rotavirus is by the faecal-oral route.  Person-to-person spread via contaminated hands is probably the most important transmission route in close communities such as paediatric and geriatric wards, day care centres and family homes.  The virus can survive for hours on human hands and for days on the surfaces of objects such as toys and work surfaces.  The virus is stable in the environment, so transmission can occur through ingestion of contaminated water or food and contact with contaminated surfaces. 

Fact sheet

Tests per kit20 
Storage15-30°C  (room temperature)
Procedural steps2
Reagents1
Hands-on time< 1 minute
Time to results≤ 15 minutes
Sensitivity100%
Specificity100%
Analytical sensitivity24.3ng/ml (ng of virus particles)

Performance data

Comparison

Sites I & II U.S.
Electron Microscopy

Site III Japan
Meridian Rotaclone® (EIA)

+

-

+

-

Xpect
Rotavirus

+

50

0

13

2

-

0

50

0

70

 

Performance
statistics
Value95% C.I. Value95% C.I.
Sensitivity

100%

92.9%-100%

Relative
sensitivity

100%

75.3%-100%

Specificity

100%

92.9%-100%

Relative
specificity
97.2%90.3%-99.7%
Agreement

100%

96.4%-100%

Relative
agreement

97.7%

91.8%-99.7%

Note: Please be advised that “relative” refers to comparison of assay results to that of a similar assay (not the gold standard).  No attempt was made to correlate assay results with disease presence or absence.  No judgment can be made on the accuracy of the comparison assay to predict disease.

Principle of the test
The Xpect Rotavirus test utilizes a pair of rotavirus-specific antibodies in an immunochromatographic sandwich assay.  An extract is first prepared by suspension of the specimen in the provided extraction buffer solution.  The buffer containing the extracted specimen is then added to the device sample well.  The reaction between a positive sample and the coloured particle-conjugated antibody will form a complex that migrates along the membrane.  An immobilized capture antibody will form a coloured line at the S (specimen) area upon reacting with the coloured complex.  An internal control line C (control) area is built-in to ensure that the test has been performed correctly.

Procedure

  1. Allow the kit components and specimens to equilibrate to room temperature prior to testing.
  2. Mix stool specimen thoroughly prior to testing (regardless of the consistency).
  3. Using a swab, add sufficient stool specimen (30-50mg) to an Xpect Rotavirus Extraction Buffer tube.
  4. Rub swab meticulously against the inner wall of tube in order to release the faecal material.
  5. For best results, vortex the tube for 60 seconds.  Allow the sediment to settle for 2-5 minutes before performing the test.

    Note:  To produce a supernatant that will allow proper migration along the test device membrane, centrifuge thick or mucoid stools after extraction at a speed capable of producing a pellet (12,000g).
  6. Remove the test device from the foil pouch when ready to perform the test and place it on a flat surface.
  7. Using the provided transfer pipettes, dispense 4 drops of the supernatant into the round sample well of the device (see illustration below).  Wait for coloured lines to appear.
  8. Read results at 15 minutes.  Some positive results may be observed very quickly (i.e., 30 seconds) depending on the concentration of antigen.  Do not interpret results after 30 minutes.

Interpretation

Negative results:
The test is negative if only one coloured line appears in the C (control) area.

Positive results:
The test is positive if two coloured lines appear.  One coloured line will appear in the S (specimen) area and one in the C (control) area.  Any coloured line in the S area should be considered positive.  Coloured lines may be lighter or darker than each other.

Invalid results:
The test is invalid if no coloured line appears in the C (control) area, even if a coloured line appears in the S (specimen) area.  If this occurs, add 1 to 2 additional drops of sample and wait for 5 minutes.  If a coloured line does not appear in the C area, the test is invalid and should be repeated.  If the line in the C area still does not appear, contact Oxoid Technical ServiceColoured lines, which appear after 30 minutes are not diagnostic and should be ignored.

References
1. Frost & Sullivan U.S. Rapid Tests Markets, March 2005.
2. CAP & API Proficiency Survey Data by Domestic End-User.

Sources:
Centers for Disease Control and Prevention: Respiratory and Enteric Viruses Branch.  (January 20, 2005).  Retrieved February 28, 2006 from www.cdc.gov/ncidod/dvrd/revb/gastro/rotavirus.htm

Centers for Disease Control and Prevention: National Immunization Program.  (February 14, 2001).  Retrieved January 19, 2006 from www.cdc.gov/nip/diseases/rota/rotavirus.htm

 

 
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