Public Health and Environmental Laboratories

Synonyms: N/A

Program: Virology

Unit: Viral Serology

Useful For: The presumptive detection of antibodies to Zika virus in persons meeting Centers for Disease Control and Prevention (CDC) clinical and or epidemiological criteria for Zika virus testing.

Method: IgM Antibody Capture Enzyme-Linked Immunosorbent Assay (MAC-ELISA)

Charge: N/A

Request Form: SRD-1

Container/ Tube: Serum separator tube

Type: Acute and convalescent human serum, cerebrospinal fluid (CSF) specimens (may only be tested when submitted alongside a patient matched serum specimen)

Volume: 2-5 mL

Collection Instructions: Venipuncture

Storage: Store all diagnostic specimens at 2-8 C or ≤ -20 C. Avoid repeated freeze-thaw cycles.

Causes for Rejection: grossly hemolyzed, lipemic, or icteric specimens, leakage, or breakage

Interpretation: Specimens with P/N values <2 are reported as negative. Specimens with P/N values ≥2 and <3 are reported as equivocal. Specimens with P/N values ≥3 are reported as presumptive positives.

Reference Interval: Negative

Limitations: Interpretation of Zika MAC-ELISA results must account for the possibility of false negative and false positive results. False-negative results can arise from:

• Specimen collection conducted before IgM has reached detectable levels (typically around 4 days’ post onset of symptoms)
• Specimen collection conducted after IgM levels have decreased below detectable levels (typically around 12 weeks’ post onset of symptoms)
• Failure to follow the authorized assay procedures
• The most common cause of false positive results is cross reactivity with IgM specific for other flaviviruses such as dengue virus. Only limited evaluation of cross-reactivity with flaviviruses or arboviruses has been conducted. No evaluation of cross-reactivity with Rheumatoid Factor has been conducted. Clinical data indicate cross-reactivity with anti-dengue virus antibodies is likely. Follow-up testing is necessary to rule-out a false-positive result. Confirmation of the presence of anti-Zika IgM requires testing by CDC or a CDC-designated laboratory. The gold-standard method for confirmation of the presence of anti-Zika antibodies is the plaque reduction neutralization test (PRNT).
• All Zika testing must be conducted following the CDC-issued Zika laboratory guidance and testing algorithms.
• Negative results do not preclude infection with Zika virus and should not be used as the sole basis of a patient treatment/ management decision. All results should be interpreted by a trained professional in conjunction with review of the patient’s history and clinical signs and symptoms.
• This assay is for in vitro diagnostic use under FDA Emergency Use Authorization only and is limited to qualified laboratories designated by the CDC.
• All specimens should be handled as if infectious. Proper biosafety precautions, including personal protective equipment, must be used when handling specimen materials.
• Proper collection, storage and transport of specimens are essential for correct results.

Availability: N/A