National Veterinary Services Laboratories 

Pseudorabies –Virus Neutralization (PRV-VN) 

Proficiency Test Summary 

1. Composition of proficiency test panel: The panel consists of twenty, 500 μl samples of 

sera. The panel contains positive and negative sera. The samples are labeled with numbers 1-20.

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. Then click on the Reagents and Proficiency Tests link.

3. Storage conditions: Short term (up to 7 days) store at 4° ± 2° C. Long term (over 7 days) 

store at <-20° C in a non-frost free freezer.

4. Sample preparation/selection criteria: Samples with positive and negative results are

chosen for incorporation into the panel. Antibody levels arise from naturally and experimentally 

acquired infections. Each panel member is tested at least five (5) times by a minimum of two 

technicians in the Diagnostic Virology Laboratory (DVL), at NVSL.

5. Panel quality control: Samples are monitored for stability and reproducibility. Sera are 

filtered prior to bottling.

6. Timing of the proficiency test distribution and data collection: The PRV-VN panel is 

administered once a year generally in January for United States approved laboratories. The 

panel is administered internationally upon request.

7. Test method: Performance and interpretation of the Pseudorabies – Virus Neutralization 

should be conducted as outlined in NVSL SOP-BPA-2112 for BPA personnel. Approved 

laboratories are not required to follow NVSL SOP-BPA-2112 at this time.

8. Submitting test results: Participants are required to have data submitted for scoring no more 

than three (3) weeks after panel distribution. Results are reported to the Head of the 

Bovine/Porcine/Aquaculture Section in the DVL, at NVSL, or designee, by fax, e-mail, or mail. 

9. Scoring of individual panel samples: Scoring is based on two criteria: proper identification 

of positive and negative samples and accuracy of reported titers. Identity scores are determined 

by assigning one point per sample correctly identified as negative (less than 1:4) or positive (any 

titer). 

Accuracy scoring is determined by assigning one point per sample for the expected titer. 

Reported titers within one two-fold dilution of the expected titer are also assigned one point. For 

a four-fold difference in titer from the expected result, 0.33 point is subtracted; for an eight-fold 

difference, 0.67 point is subtracted. Reported titers that differ more than eight-fold from the 

expected titer received zero points for accuracy.

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10. Personnel pass/fail criteria: Identification scores and accuracy scores must be at least 

15/20 to pass. Personnel with one or both scores > 15 and <18 are provided a copy of NVSL 

SOP-BPA-2112.

11. Reporting laboratory test scores (U.S. laboratories only): Results for each person are 

reported to the individual laboratory director and the AVIC. Pass letters are sent to laboratory 

directors within 60-90 days of the deadline for receipt of participants’ results.

12. Remedial actions required for failing laboratory personnel (U.S. laboratories only):

Personnel are given a second chance to pass a proficiency panel. If they fail a second time, PRV 

testing by that person is stopped, personnel must undergo training (defined by NVSL), and the 

person must pass a panel before testing can begin again.

13. Special requirements (U.S. laboratories only): Laboratories must meet requirements 

stated in the Code of Federal Regulations (CFR) title 9, part 85.

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