Viral antigens and nucleic acids may be focal and sparsely distributed in patients with influenza. Larger airways (particularly primary and segmental bronchi) have the highest yield for detection of influenza viruses by IHC staining.  In comparison, viral RNA is more commonly detected in lower airways. Collection of the appropriate tissues ensures the best chance of detecting the virus by immunohistochemical stains and PCR tests.

Collection of tissue specimens: The preferred specimens would be a minimum of 8 blocks and fixed tissue specimens representing samples from the following pulmonary sites in addition to specimens from other organs showing pathology. Fresh-frozen tissue of airways and lung should also be submitted for culture and molecular-based assays.

1. Central (hilar) lung with segmental bronchi, right and left primary bronchi, trachea (proximal and distal)
2. Representative pulmonary parenchyma from right and left lung
3. For patients with suspected myocarditis, encephalitis, or rhabdomyalysis, specimens should include myocardium (right and left ventricle), CNS (cerebral cortex, basal ganglia, pons, medulla, and cerebellum), and skeletal muscle, respectively.
4. Specimens should be included from any other organ showing significant gross or microscopic pathology.

Submission of specimens:

1. Paraffin-embedded tissue blocks: In general, this is the preferred specimen and is especially important to submit in cases where tissues have been in formalin for a significant time.  Prolonged fixation (>2 weeks) may interfere with some immunohistochemical and molecular diagnostic assays.
2. Wet tissue:  If available, we also highly recommend that unprocessed tissues in 10% neutral buffered formalin be submitted in addition to paraffin blocks. 
3. Unstained slides: Although not optimal, it may be possible to utilize unstained sections cut at 3-5 microns (10 slides per block) if paraffin blocks are unavailable.
4. Fresh-frozen tissue: (sent separately on dry ice)

Required supporting electronic or hard-copy documentation:

1. A brief clinical history
2. Copy of the preliminary or final pathology report
3. Copy of any pertinent laboratory reports (including rapid antigen, culture, and PCR test results)
4. The full name, title, complete mailing address, e-mail address, phone and fax numbers of the submitter.  (This person will receive copies of the final report)

General Guidelines for Shipping Pathology Specimens

^§Shipping Considerations:

1. Domestic packages should be mailed Monday-Wednesday for receipt by Friday.
2. International packages should also be mailed so as to be received by Friday and may require an import permit. If needed, this permit can be provided following phone consultation. 
3. U.S. Federal holidays should be taken into consideration before mailing the packages.  Exceptions can be made on urgent cases with prior approval.
4. Specific regulations for packaging, labeling, and shipping may be found at http://www.cdc.gov/ncidod/srp/specimens/shipping-packing.html, http://www.iata.org/whatwedo/cargo/dangerous_goods/infectious_substances.htm, and at http://www.cdc.gov/od/ohs/biosfty/shipdir.htm,
5. Please provide us with the shipper’s package tracking number(s).

* During the warmer months (June-Aug), in order to prevent the melting of paraffin-embedded tissue blocks during transit, it is advisable to ship the block(s) with a frozen gel ice-pack.

￥  When shipping frozen specimens from long distances or from international locations, it is best to use a combination of dry-ice and frozen gel ice-packs.  The gel ice-packs will remain frozen for a day or two after the dry-ice has dissipated.