What is the recommended test to determine varicella immunity?

Recommended Test for Determining Varicella Immunity

Commercial enzyme-linked immunosorbent assay (ELISA) for varicella-zoster virus (VZV) IgG is the recommended test to determine varicella immunity in most clinical settings. 1

Understanding Varicella Immunity Testing Options

Standard Commercial Tests

• VZV IgG ELISA: Preferred first-line test for screening purposes

  • Higher specificity compared to other commercial tests
  • Recommended by the CDC for healthcare personnel screening 1
  • Detects IgG antibodies that develop and persist long-term after vaccination or natural infection

• Latex Agglutination (LA) Test:

  • More sensitive than standard ELISA but less specific
  • May produce false-positive results, particularly when using only a single concentration of serum 1
  • Not recommended as first-line testing due to potential false positives

Specialized Research Tests (Not Commercially Available)

• Fluorescent Antibody to Membrane Antigen (FAMA) assay:

  • Considered the gold standard reference test 2, 3
  • Higher sensitivity but not commercially available for routine clinical use
  • Used primarily in research settings

• Glycoprotein ELISA (gpELISA):

  • Higher sensitivity than standard commercial ELISAs
  • Used in clinical trials and research settings
  • Not widely available for routine clinical use 2, 3

Limitations of Commercial Tests

Commercial assays have important limitations to be aware of:

• Standard commercial ELISAs may fail to detect vaccine-induced immunity despite actual protection in approximately 25-34% of vaccinated individuals 1
• These tests were originally designed to detect the higher antibody levels from natural infection rather than the lower levels induced by vaccination 1
• After one dose of varicella vaccine, only 76-90% of healthy children develop detectable protective antibody levels 2

Special Considerations for Different Populations

Healthcare Workers

• CDC recommends screening all healthcare personnel using VZV IgG testing 1
• Serologic screening before vaccination is cost-effective in healthcare settings
• If negative for VZV IgG, vaccination with 2 doses of varicella vaccine at least 4 weeks apart is recommended 1

Immunocompromised Patients

• Patients with inflammatory bowel disease or other immunocompromising conditions should be screened by history or IgG testing 1
• For immunocompromised patients with negative standard IgG results despite documented vaccination, more sensitive testing methods may be warranted 1

Post-Vaccination Testing

• Routine testing after vaccination is not recommended due to limitations in commercial assays 1
• If testing is required for special circumstances (e.g., healthcare workers), standard VZV IgG ELISA should be used

Common Pitfalls to Avoid

1. Relying on IgM testing for immunity assessment: IgM antibodies appear transiently during acute infection but are not reliable indicators of vaccination status or long-term immunity 1

2. Using self-reported history without verification: Self-reported history without healthcare provider verification may be unreliable 1

3. Misinterpreting negative results in vaccinated individuals: Commercial tests may show negative results in vaccinated individuals who actually have protective immunity 1

4. Using serology for diagnosis of active disease: Serology is not useful for diagnosis of active chickenpox or shingles lesions - direct detection methods from lesion samples are preferred 1

In summary, while specialized tests like FAMA and gpELISA have superior sensitivity, commercial VZV IgG ELISA remains the practical and recommended test for determining varicella immunity in routine clinical practice.