Antibody Detection


  • Test Code


  • CPT Code

    86698 x2

  • Clinical Significance

    IgM and IgG antibodies to Histoplasma antigen usually appear during the first month of infection. The IgM antibody response in acute pulmonary histoplasmosis is detectable during the acute phase (roughly 3 weeks) and is shown to decline during the convalescent stage (at about 6 weeks); whereas, IgG levels remained relatively constant at 6 weeks. Follow-up testing may be considered 2-4 weeks after initial testing to determine if antibody levels are increasing, especially in patients with low positive (10 EU – 20 EU) or intermediate results. Increase in IgG antibody or decrease in IgM concentration would suggest recent infection. Antibodies may persist for several years in patients with chronic pulmonary complications or progressive extrapulmonary (disseminated) histoplasmosis. Antibodies may be falsely-negative in some progressive or chronic cases, especially in immunocompromised patients. Antibodies may also be detected in healthy subjects who are asymptomatic as a result of sub-clinical infection within the last 18-36 months.

  • Methodology

    Semi-Quantitative Indirect Enzyme Immunoassay (EIA)

  • Limitations
    • 12% cross reactivity with Blastomycosis
    • 24% cross reactivity with Coccidioidomycosis
  • Specimen Collection

    Serum: Collect serum specimens in serum separator or red top tube. Allow blood to clot for 30 minutes, then centrifuge. Pipette serum into a plastic screw cap vial.

    CSF: Sterile transport tube.

  • Minimum Specimen Requirements

    Serum/CSF: 0.5 mL

  • Specimen Stability
    • Room Temperature: 14 days
    • Refrigerated: 14 days
    • Frozen: 14 days
  • Specimen Rejection
    • >14 days old
    • Any specimen types other than serum or CSF
    • For specimen submissions that do not meet this criteria, please call Customer Service
  • Transport Temperature


  • Shipping

    Ship on dry ice to arrive Monday‐Friday using a next day delivery service. Frozen ice packs may be substituted if sample is shipped the day of collection.

  • Turnaround Time

    Testing performed Mondays and Thursdays.

    Serum or CSF: TAT reported next day

  • Reference Range


  • Interpretative Information
    • Negative: <8.0 EU
    • Intermediate: 8.0 EU-9.9 EU
    • Positive: 10.0 EU-80.0 EU
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