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Nov 2013

National Veterinary Services Laboratories

Bovine Spongiform Encephalopathy (BSE) 

and Chronic Wasting Disease (CWD)

ELISA Proficiency Test Summary

1. Composition of proficiency test panel: The BSE/CWD panel consists of a 

minimum of five samples. The samples are sheep brain homogenates for the BSE PT 

and/or CWD brain and/or lymph node homogenates for the CWD PT. A varying

number of Positive and Not Detected samples will be used.

2. Cost of proficiency test: Click here to view current NVSL Catalog of Reagents.

Additional information on diagnostic reagents, including ordering, payments, shipping

details and fees, is located at www.aphis.usda.gov/nvsl. Click on the Reagents and 

Proficiency Tests link. 

Currently there is no charge to NAHLN approved laboratories (subject to change). 

Currently there is no charge to other laboratories (subject to change).

3. Storage conditions: Samples are stored frozen at a temperature -20°C or lower.

4. Sample preparation/selection criteria: Known scrapie positive and negative sheep

brain samples and/or CWD brain and/or lymph nodes for the CWD PT (as determined 

by IHC) are homogenized and pooled. These pooled samples are then tested by ELISA

and if determined to be appropriate - Positive samples (> 0.500 OD) and Not Detected

(no more than three times the mean negative control value) - are used in the panels.

5. Panel quality control: The samples are first identified by IHC as positive, and

NVSL tests the pooled homogenates by ELISA prior to sending out the panels.

6. Timing of the proficiency test distribution and data collection: The PT is issued

annually with a target of the 2nd FY quarter (Jan-Mar). PTs may be sent to

laboratories upon request, at the discretion of the PT manager.

7. Test method: The PT samples are tested by ELISA.

8. Submitting test results: The testing is done in duplicate. Participants are required to

have both sets of ELISA results submitted to NVSL (Head of Pathology, Parasitology, 

and Entomology and/or designee) not later than 10 days after panel has been received by

the participant.

9. Scoring of individual panel samples: For each panel a score is based on number of

homogenates with correct interpretation by the participant.

10. Laboratory pass/fail criteria: A final score of 100 percent correctly identified

samples is considered as a passing score.

11. Reporting laboratory test scores: Participating laboratories are required to run the
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Nov 2013

ELISA samples in duplicate on different days. The participant laboratory should run the

samples and report the ELISA results to the appropriate NVSL personnel. The laboratory

should wait for an affirmative response from NVSL before running the second test. Final

run results should be reported within 10 days of receipt. NVSL will share by

(email/postal mail), the results with each individual participant (Laboratory Director or 

designee) within 10 days from receipt of the last panel results.

12. Remedial actions required for failing laboratories: If discrepant results are

obtained an investigation as to the cause will be done by NVSL, the participating

laboratory, and others as required. If the apparent cause of the discrepant results are

determined and rectified to the satisfaction of NVSL no additional corrective actions may

be needed. At the discretion of NVSL, additional PT panels or additional training of

personnel may be required. A second failure of a PT may be grounds for removal of

testing approval.

13. Special requirements: Restrictions: A USDA permit is required to obtain the panel.

Failure on the part of participate laboratories to maintain current permits may result in

withdrawal of approval until such time as a permit and PT test can be administered.