Development of a proficiency testing program for molecular diagnosis of influenza viruses

Abstract

Background: The Molecular Virology Proficiency Testing Program at the Wadsworth Center began the assembly and distribution of influenza virus panels to US public health labs (PHLs) in 2008. The program was created to assist PHLs in assessing their performance and in meeting CLIA regulations for mandated proficiency testing (PT).

Objectives: To design and distribute proficiency testing panels containing influenza A virus subtypes H1N1 and H3N2, and influenza B; when H1N1pdm09 emerged it also was incorporated into the panels. A secondary objective was to determine the best matrix for long term storage of the molecular PT samples.

Study design: Viruses were quantitated using TCID(50) and quantitative real-time RT-PCR. Reference laboratories were enlisted to verify viral identity in the panels and to help determine viral titers to be used in the PT panels sent to PHLs.

Results and conclusions: Of the 29 laboratories that participated the first year, 27 were able to correctly identify all of the virus types in the panel. Fifty-one PHLs participated in the program the second year when pandemic H1N1 was added, and 45 were able to correctly detect, type and subtype all of the viruses in the panel. In the program's third year, 60 laboratories participated; 58 correctly detected and subtyped all of the viruses in the panel. Annual surveys of assay techniques showed that the PHLs had shifted their extraction methods and PCR-thermocycler instrumentation to meet FDA-approved methods. The degradation study revealed that frozen viral stocks were stable for at least 30months, thus allowing ample time to prepare and pre-test panels.