Dengue Literature Review

IgM-IgG Serology ELISA

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IgM/IgG Serology ELISA

Overview

Enzyme-linked immunosorbent assay (ELISA) detection of dengue-specific IgM and IgG antibodies is the most widely used method for dengue diagnosis globally. IgM-capture ELISA (MAC-ELISA) detects acute-phase IgM from approximately day 5–6 of illness. IgG ELISA, when used with paired acute and convalescent sera, can confirm seroconversion or identify secondary (heterotypic) infection by the magnitude of the anamnestic IgG response. Serological methods do not distinguish between the four DENV serotypes and cannot replace molecular methods for early acute-phase diagnosis.

Key Points from Literature

Timing and diagnostic windows

  • IgM: appears from day 5–6 of illness; peaks at 2 weeks; may persist for 2–3 months; the primary tool for mid-to-late acute and early convalescent diagnosis
  • IgG: rises from approximately day 7–10 in primary infection; in secondary infection, an anamnestic IgG response appears very rapidly — detectable within 1–2 days of illness onset at high titres (>1,280 by HI or ELISA)
  • Diagnostic gap: days 1–5 of illness are not covered by serology; during this window, only RT-PCR and NS1 Antigen Detection are informative (see Guzman2016 - Dengue Infection)

Presumptive diagnosis criteria

  • Single serum: positive IgM = presumptive dengue (in endemic settings with appropriate clinical presentation)
  • Single serum: IgG titer ≥1,280 by haemagglutination inhibition (HI) or ELISA = presumptive secondary dengue infection
  • Paired sera: seroconversion from negative to positive IgM, or ≥4-fold IgG titer rise between acute and convalescent samples = confirmed dengue

Primary vs secondary infection discrimination

  • In primary dengue: IgM > IgG; low IgG early in illness; IgG titer in convalescent phase typically < 1:1,280
  • In secondary dengue: IgG dominates; high IgG from day 1–2 due to anamnestic memory B cell response; IgG:IgM ratio > 1.2 is a common threshold for secondary infection classification in research settings
  • This discrimination is important because DHF/DSS risk is substantially higher in secondary infection (see Antibody-Dependent Enhancement)

Formats

  • MAC-ELISA (IgM-capture ELISA): most widely used; commercial kits available globally; used in WHO-recommended intermediate-level laboratory testing
  • IgG indirect ELISA: paired sera preferred; single high-titer IgG useful in secondary infection context
  • Combined NS1 + IgM + IgG RDT: lateral flow devices detecting all three in one cassette; field-applicable; used where ELISA infrastructure unavailable
  • PRNT (plaque reduction neutralisation test): gold standard serological assay for definitive serotype-specific neutralising antibody measurement (see PRNT); not an ELISA but often paired with ELISA in reference settings

Zika cross-reactivity (post-2015 complication)

  • Zika virus is a flavivirus closely related to DENV; dengue IgM ELISA cross-reacts with Zika antigens
  • False-positive dengue IgM serology in Zika-infected patients is documented
  • Post-2015 recommendations: wherever Zika co-circulates (most dengue-endemic regions in the Americas, Pacific islands), dengue-positive serology should be reflexively confirmed with Zika-specific testing
  • This complication significantly complicates dengue surveillance data from 2015 onwards in Zika-co-endemic areas (see Guzman2016 - Dengue Infection)

Placement in WHO diagnostic tiered structure

  • Intermediate level: MAC-ELISA (recommended by WHO for district-level labs)
  • Field level: combined RDTs (IgM/IgG ± NS1)
  • Reference level: PRNT for definitive serotype-specific confirmation; paired IgG titration

Contradictions & Debates

  • Single IgM positivity has lower predictive value in very low-prevalence settings (more false positives) and in areas of Zika co-circulation; clinical judgement and paired testing recommended
  • IgG titer thresholds for secondary infection classification vary by assay and region; no single internationally validated cut-off for routine diagnostics

Sources

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