Clinical Specimen Collection and Handling
Unexplained Critical Illnesses and Deaths

Testing provided through the Unexplained Critical Illness and Deaths Project for unexplained deaths that appear likely to have infectious etiologies will be primarily pathology-directed. Therefore, it is important when possible to provide optimal pathology specimens.

These clinical specimens may be useful in determining an etiology for cases of unexplained illness or death that are likely to have infectious causes. These specimens should be saved for possible cases. While timing of collection and volume of some specimens may not be optimal, it may still be possible to use them for testing.

On this page:
Types of specimens
Specimen collection and handling
Laboratory specimens
Shipping

Types of specimens

• Two types of specimens are needed in order to provide a complete evaluation:
  
  
  • Fixed tissue
    
    
  • Fresh frozen tissue
    
    
• Body fluids are also helpful
  
  
• A nasopharyngeal swab can also be collected if a respiratory infection is suspected
  
  

Specimen collection and handling

Ideally, tissue for CDC would be collected separately at the time of autopsy and would include tissue from each organ and from several areas of each organ. Fixed tissue from multiple organs can be combined in one container.

If specimens are limited, priority should be given to providing fixed tissue, especially from the primary affected organ (for example, brain tissue for a meningoencephalitis case). If a specifically affected area is noted by gross pathology or preliminary histopathology, it is helpful to submit tissue from this area.

Fixed tissue

• Fixed tissue should either be in 10% buffered formalin or paraffin-embedded
  
  
• Fixed tissue is used for routine H&E stains and special stains as well as immunohistochemistry and in situ hybridazation.
  
  
• If fixed tissue is submitted to CDC more than 2 weeks after it is collected, paraffin-embedded tissue is preferred for submission.
  
  
• Over-fixation will form a strong formalin bond in tissue and make antigen retrieval more difficult.
  
  
• Blocks rather than slides are also preferred since epitopes and nucleic acids can degenerate more quickly once tissue is prepared for slides thus decreasing sensitivity of special assays.
  
  
• Fixed tissue from multiple organs can be combined in one container.
  
  
• Fixed tissue should be stored and shipped at room temperature.
  Do not freeze fixed tissue.
  

Fresh frozen tissue

• Frozen tissue is used for culture and molecular techniques including specific primer and consensus polymerase chain reaction (PCR).
  
  
• Specimens should be collected aseptically and as soon as possible after death.
  
  
• A separate sterile instrument should be used for each collection site and each specimen should be placed in a separate sterile container in small amounts of viral transport media or saline.
  
  
• Frozen tissue should be stored at -70°C and shipped on dry ice.

Body fluids

• 5-10 cc of cerebrospinal fluid and 5 cc of heart blood (in a marbled red tube top) collected postmortem may also be used for testing.
  
  
• Body fluid specimens should be kept refrigerated and shipped with a cold pack (or dry ice if specimens are being sent directly to CDC).
  
  
• Please refer to the laboratory specimens chart for information on collection and handling of body fluid specimens obtained prior to death.

Nasopharyngeal swab

• If a respiratory infection is suspected, a postmortem nasopharyngeal swab can be collected and sent to the Minnesota Department of Health (MDH) in a sterile container with viral transport media for viral culture.
  

Laboratory specimens

• Laboratory Specimens: Collection and Handling of Clinical Specimens (PDF)
  A chart listing clinical specimens, optimal timing of collection, optimal volume, container type, and temperature for storing and shipping.
  
  
• Unexplained Critical Illnesses Specimen Submission Form (PDF)
  Specimen submission form for unexplained critical illnesses. Updated 4/2020
• Unexplained Death Specimen Submission Form (PDF)
  Specimen submission form for unexplained deaths. Updated 4/2020
  
  

Shipping

• Each specimen container should be labeled with a case identification number assigned by MDH (call 651-201-5414 for a case number).

• A pathology/autopsy report should accompany pathology specimens.

• Identifying information such as name, address, and medical record number may be removed. Preliminary reports are acceptable.

• A list of specimens being sent should also be included.

  • Fixed tissue should be shipped in a separate package from body fluids and/or frozen tissue.
  • Fixed tissue should be sent at room temperature while frozen tissue and body fluid should be sent on dry ice.
    
    
• Specimens may be sent directly to CDC or arrangements may be made for specimens to be picked up or delivered to MDH where they will be forwarded to CDC.
  
  
• Please call 651-201-5414 for more information on shipping.