Evaluation of total immunoglobulin G and subclass antibodies in an enzyme-linked immunosorbent assay for serodiagnosis of human amebic liver abscess.

Background: Amebic liver abscess (ALA) caused by is usually diagnosed based on its clinical symptoms, medical imaging abnormalities of the liver, and serological tests, the most common being the enzyme-linked immunosorbent assay (ELISA). For more than three decades, no investigation has evaluated the diagnostic performance of immunoglobulin G (IgG) subclasses in the serodiagnosis of ALA. Herein, we assessed the efficiencies of anti-amebic IgG and IgG subclasses for diagnosing ALA.

Methods: A serological ELISA-based test was performed to assess its diagnostic performance using a total of 330 serum samples from ALA patients ( = 14), healthy individuals ( = 40), and patients with other diseases ( = 276).

Results: ELISA targeting the total IgG antibody to antigen exhibited 100% sensitivity 95% CI [76.8-100.0] and 97.8% specificity 95% CI [95.5-99.1], whereas the assay targeting IgG1 showed the same sensitivity (100% 95% CI [76.8-100.0]) and a slightly higher specificity (99.1% 95% CI [97.3-99.8]). The other IgG subclasses (IgG2, IgG3, and IgG4) displayed a lower sensitivity and specificity. The sensitivity and specificity did not significantly differ between tests measuring total IgG and IgG1 (Exact McNemar's test; > 0.05), with a concordance of 98.2%, represented by a Cohen's kappa of 0.83 ( < 0.001), indicating almost perfect agreement.

Conclusion: ELISA targeting IgG1 can provide valuable information to clinicians in differentiating ALA from other parasitic diseases, cancers, cirrhosis, and viral hepatitis. However, enzyme-conjugated anti-human total IgG is cheaper than anti-human IgG subclasses. Therefore, we suggest that total IgG-based ELISA is sufficient for the routine serodiagnosis of human ALA and possibly other clinical manifestations of invasive amebiasis.