Lassa fever laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Ammu Susheela, M.D. [2]

Overview

Acute Lassa fever is usually diagnosed by detection of IgG Lassa antibodies in the patient's serum using ELISA. Additional investigations are also required following diagnosis to monitor the course of the disease for development of complications and target organ damage.

Serology

• The mainstay of diagnosis of Lassa fever is detection of Lassa antibodies in the patient's serum.
• Patients with acute Lassa fever typically have high concentration of Lassa IgG antibodies, whereas patients already infected in the past have high IgM Lassa antibodies.

Other Laboratory tests

• Additional work-up is necessary following diagnosis to monitor the course of the disease for development of complications and target organ damage.
• The following table summarizes the lab tests and findings associated with Lassa fever:

Laboratory findings

Lab Tests	Laboratory Findings
Complete Blood Count	Lymphocytopenia, thrombocytopenia
Liver function tests	Elevated aspartate aminotransferase (AST)
Urinalysis	Proteinuria
Chest X-rays	Chest X-rays typically demonstrates basilar pneumonitis and pleural effusions.
Viral culture	The virus often delays the diagnosis and may be cultured in 7 to 10 days.
Viral isolation	Viral isolation is the most sensitive technique for the detection of Lassa virus, but it is infrequently used except in research. The virus may be observed under electron microscopy. Obtain samples from blood, urine, pleural effusion, or throat swab of living patients or from tissue samples (either liver, kidney, spleen, or heart) of dead patients.

Handling of Laboratory Samples

Guidance for Collection, Transport, and Submission of Specimens for Virus Testing

• Lassa virus is graded as biosafety level 4 according to The Centers for Disease Control and Prevention (CDC) classification.
• Ideally, specimens should be taken when a symptomatic patient reports to a healthcare facility and is suspected of having an exposure to the disease. However, if the onset of symptoms is <3 days, a later specimen may be needed to completely rule-out virus, if the first specimen tests negative.
• A minimum volume of 4 mL of whole blood preserved with EDTA is preferred, but whole blood preserved with either sodium polyanethol sulfonate, citrate, or clot activator may be submitted for testing. Heparin tubes are not recommended.
• Specimens should be shipped at 2-8°C or frozen on cold-packs, but not in glass containers.

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 virus specimen.
• Packing and shipping infectious substances must be performed by people trained and certified in compliance with DOT or International Air Transport Association requirements.

Gallery

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  This transmission electron micrograph depicted eight virions (viral particles) of a newly-discovered virus, which was determined to be a member of the genus, Arenavirus. From Public Health Image Library (PHIL).