Specimen Submission Guidelines for Pathologic Evaluation of Unexplained Illness due to Possibly Infectious Etiology

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Unexplained critical illnesses and deaths of possible infectious etiology can be challenging cases to investigate. This is especially true for cases of sudden death, for which pre-mortem specimens are unavailable, and for cases where traditional laboratory assays have been unsuccessful in identifying a specific agent. Some of these cases have gross or histopathologic features suggestive of an infectious process, and may be submitted for evaluation by the Infectious Diseases Pathology Branch. Performance of specific immunohistochemical, molecular, or other assays will be determined using clinical and epidemiologic information provided by the submitter and the histopathologic features identified in the submitted tissue specimens.

Collection of Tissue Specimens

In cases where there is gross or microscopic evidence of an infection present, or when clinical history raises the suspicion of infection, tissue from the organ(s) demonstrating pathology should be sampled heavily and submitted for evaluation. Major organs without apparent histopathologic changes may be submitted representatively.

Submission of Specimens

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.

Wet tissue

If available, we highly recommend that unprocessed tissues in 10% neutral buffered formalin be submitted in addition to paraffin blocks. The volume of formalin used to fix tissues should be 10x the volume of tissue. Place tissue collected according to the dimensions provided above in 10% buffered formalin for three days (72 hours) for biopsies, and a week for thinly-sliced autopsy tissues. After fixation, if not paraffin-embedded, tissues SHOULD be transferred to 70% ethanol for long term storage and for shipping.

Electron Microscopy (EM) specimens

Samples should be fixed in glutaraldehyde and held in phosphate buffer. Sample containers are filled to the top with phosphate buffer and sent on wet ice. Do not freeze. Epoxy-embedded tissues are also accepted.

Please refer to our General Guidelines for Submitting Pathology Specimens.