Ordering Recommendation

Not recommended as a stand-alone test. Refer to Arbovirus Antibodies, IgG and IgM, Serum (2001594).

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation

Serum separator tube. Also acceptable: Plain red.

Specimen Preparation

Separate serum from cells ASAP or within 2 hours of collection. Transfer 1 mL serum to an ARUP Standard Transport Tube. (Min: 0.4 mL) Parallel testing is preferred and convalescent specimens must be received within 30 days from receipt of acute specimens. Mark specimens plainly as "acute" or "convalescent."

Storage/Transport Temperature


Unacceptable Conditions

Plasma. Contaminated, heat-inactivated, hemolyzed, or severely lipemic specimens.


After separation from cells: Ambient: 48 hours; Refrigerated: 2 weeks; Frozen: 1 year (avoid repeated freeze/thaw cycles)


Semi-Quantitative Indirect Fluorescent Antibody/Semi-Quantitative Enzyme-Linked Immunosorbent Assay


Tue, Fri


1-5 days

Reference Interval

Test Number
Reference Interval
  West Nile Virus Ab, IgM, Ser 0.89 IV or less
  California Encephalitis IgM Less than 1:16
  St. Louis Encephalitis Ab, IgM, Serum Less than 1:16
  Eastern Equine Enceph Ab, IgM Less than 1:16
  Western Equine Enceph Ab, IgM, Ser Less than 1:16

Interpretive Data

Component Interpretation
West Nile Virus Antibody, IgM by ELISA, Serum 0.89 IV or less: Negative - No significant level of West Nile virus IgM antibody detected.
0.90-1.10 IV: Equivocal - Questionable presence of West Nile virus IgM antibody detected.  Repeat testing in 10-14 days may be helpful.
1.11 IV or greater: Positive - Presence of IgM antibody to West Nile virus detected, suggestive of current or recent infection.

Compliance Category



Hotline History


CPT Codes

86651; 86652; 86653; 86654; 86788


Component Test Code* Component Chart Name LOINC
0050236 West Nile Virus Ab, IgM, Ser 38166-5
0098731 California Encephalitis IgM 10905-8
0098732 St. Louis Encephalitis Ab, IgM, Serum 10907-4
0098733 Eastern Equine Enceph Ab, IgM 10898-5
0098734 Western Equine Enceph Ab, IgM, Ser 6958-3
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


Arbovirus Antibodies, IgM, Serum