Ebola laboratory tests
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Michael Maddaleni, B.S.; Guillermo Rodriguez Nava, M.D. [2]; Rim Halaby, M.D. [3]
Overview
Several diagnostic tests are available for detection of Ebola virus disease (EVD). Acute infections are confirmed using a real-time RT-PCR assay. Virus isolation may also be attempted. Serologic testing for IgM and IgG antibodies is completed for certain specimens and is performed to monitor the immune response in confirmed EVD patients. Specimens ideally should be taken when a symptomatic patient reports to a healthcare facility and is suspected of having an Ebola exposure. Ebola infection is associated with nonspecific laboratory abnormalities including alterations in the white blood cell count, blood chemistry tests and liver function tests, all of which may contribute to a disruption in the clotting process and bleeding.
Indications for Laboratory Testing
CDC recommends testing for all persons with onset of fever within 21 days of having a high-risk exposure such as:
- Percutaneous or mucous membrane exposure or direct skin contact with body fluids of a person with a confirmed or suspected case of EVD without appropriate personal protective equipment (PPE), or
- Laboratory processing of body fluids of suspected or confirmed EVD cases without appropriate PPE or standard biosafety precautions, or
- Participation in funeral rites or other direct exposure to human remains in the geographic area where the outbreak is occurring without appropriate PPE.
For persons with a high-risk exposure but without a fever, testing is recommended only if there are other compatible clinical symptoms present and blood work findings are abnormal (i.e., thrombocytopenia <150,000 cells/µL and/or elevated transaminases).
Laboratory Tests
| Timeline of Infection | Diagnostic Tests Available |
| Within a few days after symptoms begin |
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| Later in disease course or after recovery |
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| Retrospectively in deceased patients |
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Laboratory Findings
The table below displays the nonspecific laboratory abnormalities associated with Ebola infection, including:[1]
| Test | Findings |
|---|---|
| White blood cell count | Leucopenia with lymphopenia (early) Neutrophilia (late) |
| Blood smear | Left shift Atypical lymphocytes |
| Hemostasis and Coagulation | Thrombocytopenia Consumption of clotting factors Increased concentrations of fibrin degradation products |
| Liver function tests | Elevated aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels Elevated gamma GT (GGT) and bilirubin levels Prolonged prothrombin time (PT) or international normalized ratio (INR) Prolonged partial thromboplastin time (PTT) |
| Renal function tests | Elevated serum creatinine level |
| Proteins | Hyperproteinemia |
| Metabolic | Hypokalemia Hypocalcemia |
| Urinalysis | Hematuria Proteinuria |
Guidance for Specimen Collection, Transport, Testing, and Submission in the United States
Specimen Handling for Routine Laboratory Testing (not for Ebola Diagnosis)
Routine laboratory testing includes traditional chemistry, hematology, and other laboratory testing used to support and treat patients. Recommendations to offer appropriate protection for healthcare personnel performing laboratory testing on specimens from patients with suspected infection with Ebola virus are:
- Recommendations for risk assessment to staff: Risk assessments should be conducted by each laboratory director, biosafety officer, or other responsible personnel to determine the potential for sprays, splashes, or aerosols generated from laboratory procedures. They should adjust, as needed, PPE requirements, practices, and safety equipment controls to protect the laboratorian’s skin, eyes, and mucous membranes.
- Recommendations for specimen collection by staff: Any person collecting specimens from a patient with a case of suspected Ebola virus disease should wear gloves, water-resistant gowns, full face shield or goggles, and masks to cover all of nose and mouth Additional PPE may be required in certain situations.
- Recommendations for laboratory testing by staff: Any person testing specimens from a patient with a suspected case of Ebola virus disease should wear gloves, water-resistant gowns, full face shield or goggles, and masks to cover all of nose and mouth, and as an added precaution use a certified class II Biosafety cabinet or Plexiglass splash guard with PPE to protect skin and mucous membranes. All manufacturer-installed safety features for laboratory instruments should be used.
Management of Laboratory Waste
Waste generated during laboratory testing should be placed in leak-proof containment and discarded as regulated medical waste. To minimize contamination of the exterior of the waste bag, place this bag in a rigid waste container designed for this use. If available, steam sterilization (autoclave) or incineration as a waste treatment process can inactivate the virus and reduces waste volume. For equipment that drains directly into the sewer system, the United States sanitary sewer system handling processes (e.g., anaerobic digestion, composting, disinfection) are designed to safely inactivate infectious agents. However, check with your state's regulated medical waste program for more guidance and coordinate your waste management activities for the laboratory area with your medical waste contractor.
Transporting Specimens within the Hospital / Institution
Specimens should be placed in a durable, leak-proof secondary container for transport within a facility. To reduce the risk of breakage or leaks, do not use any pneumatic tube system for transporting suspected EVD specimens.
When Specimens Should Be Collected for Ebola Testing at CDC
Ebola virus is detected in blood only after the onset of symptoms, usually fever. It may take up to 3 days after symptoms appear for the virus to reach detectable levels. Virus is generally detectable by real-time RT-PCR from 3-10 days after symptoms appear.
Specimens ideally should be taken when a symptomatic patient reports to a healthcare facility and is suspected of having an Ebola exposure. However, if the onset of symptoms is <3 days, a later specimen may be needed to completely rule-out Ebola virus, if the first specimen tests negative.
Preferred Specimens for Ebola Testing at CDC
A minimum volume of 4mL whole blood in plastic collection tubes can be used to submit specimens for testing for Ebola virus. Do not submit specimens to CDC in glass containers or in heparinized tubes. Whole blood preserved with EDTA is preferred but whole blood preserved with; sodium polyanethol sulfonate (SPS), citrate, or with clot activator is acceptable. It is not necessary to separate and remove serum or plasma from the primary collection container. Specimens should be immediately stored or transported at 2-8°C or frozen on cold-packs to the CDC. Specimens other than blood may be submitted upon consult with the CDC by calling the Emergency Operations Center at 770-488-7100.
Standard labeling should be applied for each specimen. The requested test only needs to be identified on the requisition and CDC specimen submission forms.
Storing Clinical Specimens for Ebola Testing at CDC
Short-term storage of specimens prior to shipping to CDC should be at 4°C or frozen.
Diagnostic Testing for Ebola Performed at CDC
Several diagnostic tests are available for detection of EVD. Acute infections will be confirmed using a real-time RT-PCR assay (CDC test directory code CDC -10309 Ebola Identification) in a CLIA-certified laboratory. Virus isolation may also be attempted. Serologic testing for IgM and IgG antibodies will be completed for certain specimens and to monitor the immune response in confirmed EVD patients.
Lassa fever is also endemic in certain areas of West Africa and may show symptoms similar to early EVD. Diagnostic tests available at CDC include but are not limited to RT-PCR, antigen detection, and IgM serology all of which may be utilized to rule out Lassa fever in EVD-negative patients.
Packaging and Shipping Clinical Specimens to CDC
Specimens collected for EVD testing should be packaged and shipped without attempting to open collection tubes or aliquot specimens.
Shown below is an image depicting a diagram on packaging and shipping clinical specimens of patients suspected to have EVD.
References
- ↑ Feldmann H, Geisbert TW (2011). "Ebola haemorrhagic fever". Lancet. 377 (9768): 849–62. doi:10.1016/S0140-6736(10)60667-8. PMC 3406178. PMID 21084112.