Enzyme-linked immunoassay for dengue virus IgM and IgG antibodies in serum and filter paper blood
Thanh Nga T Tran1 ,2, Peter J de Vries1, Lan Phuong Hoang1 ,3, Giao T Phan1 ,3, Hung Q Le1 ,3, Binh Q Tran3, Chi Mai T Vo2, Nam V Nguyen4, Piet A Kager1, Nico Nagelkerke5 and Jan Groen6 ,7
1Division of Infectious Diseases, Tropical Medicine and AIDS, Academic Medical Center, P.O. Box 22700, 1100 DE Amsterdam, the Netherlands Amsterdam, the Netherlands
2Department of Microbiology, Cho Ray Hospital, 102 B Nguyen Chi Thanh, Ho Chi Minh City, Vietnam
3Department of Tropical Diseases, Cho Ray Hospital, 102 B Nguyen Chi Thanh, Ho Chi Minh City, Vietnam
4Binh Thuan Malaria and Goiter Control Center, 133A Hai Thuong Lan Ong, Phan Thiet, Vietnam
5Dept of Community Medicine, United Arab Emirates University, P.O. Box 17666 Al Ain, United Arab Emirates
6Department of Clinical Virology, Erasmus Medical Center Rotterdam, The Netherlands
7Department of Microbiology and Virology, Focus Diagnostics, Cypress CA, USA
The reproducibilty of dengue IgM and IgG ELISA was studied in serum and filter paper blood spots from Vietnamese febrile patients.
781 pairs of acute (t0) and convalescent sera, obtained after three weeks (t3) and 161 corresponding pairs of filter paper blood spots were tested with ELISA for dengue IgG and IgM. 74 serum pairs were tested again in another laboratory with similar methods, after a mean of 252 days.
Cases were classified as no dengue (10 %), past dengue (55%) acute primary (7%) or secondary (28%) dengue. Significant differences between the two laboratories' results were found leading to different diagnostic classification (kappa 0.46, p < 0.001). Filter paper results correlated poorly to serum values, being more variable and lower with a mean (95% CI) difference of 0.82 (0.36 to 1.28) for IgMt3, 0.94 (0.51 to 1.37) for IgGt0 and 0.26 (-0.20 to 0.71) for IgGt3. This also led to differences in diagnostic classification (kappa value 0.44, p < 0.001) The duration of storage of frozen serum and dried filter papers, sealed in nylon bags in an air-conditioned room, had no significant effect on the ELISA results.
Dengue virus IgG antibodies in serum and filter papers was not affected by duration of storage, but was subject to inter-laboratory variability. Dengue virus IgM antibodies measured in serum reconstituted from blood spots on filter papers were lower than in serum, in particular in the acute phase of disease. Therefore this method limits its value for diagnostic confirmation of individual patients with dengue virus infections.
However the detection of dengue virus IgG antibodies eluted from filter paper can be used for sero-prevalence cross sectional studies.
BMC Infectious Diseases 2006, 6:13. Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0.