Immunoglobulin G (IgG) to IgM ratio in secondary adult dengue infection using samples from early days of symptoms onset

BACKGROUND Dengue virus (DENV) infection is an emerging arboviral infection in tropical and sub-tropical countries in South-East Asia, the Western Pacific and South and Central America. Secondary DENV infection is the most widely accepted risk factor for the development of severe forms. Methods to discriminate primary and secondary DENV infection may be of great prognostic value. ELISA based detection of specific antibodies (IgG and IgM) to the four DENV serotypes is valuable for determination of primary or secondary infection. Several studies had been performed to discriminate primary and secondary DENV infection using the ratio of IgG and IgM at the various days of symptoms onset. The aim of this study is to determine the best cut-off point of IgG to IgM ratio is able to discriminating secondary from primary DENV infection in adult using samples from early days of symptoms onset. METHODS This prospective cohort study on 48 adult patients with DENV infected patients on the period of August 2011-January 2012 in 5 out-patient settings health facilities in Tangerang district, Banten province, Indonesia with chief complaint of fever less than 3 days. Datas were collected on the day the patients attended health facilities, consisted of demographic, clinical, laboratory, and serological data. Serological data from 48 serum sample from adult patients were evaluated using Focus Diagnostics Dengue Virus IgM and IgG Capture DxSelect™ ELISA Kits to determine IgG, IgM index values and SD Bioline Dengue Duo™ Rapid Tests to determine NS1, IgG, and IgM result. RESULTS According to NS1, IgG and IgM results, 36 patients were classified as secondary infection, 12 were primary Infection. The mean (SD) of IgG/IgM ratios for secondary and primary infection were 3.28 (0.54) and 0.18 (0.11) consecutively. The IgG/IgM ratio of ≥ 1.14 confirmed secondary infection with sensitivity of 80.56 %, specificity 91.67 %, accuracy level 83.33 %, and likely hood ratio of (LR) 9.67. CONCLUSION The IgG/IgM ratio of ≥ 1.14 as the best cut off point to determine secondary DENV infection in early days of symptoms onset.