Estimation of dengue virus IgM persistence using regression analysis

Abstract

Dengue virus IgM persistence was estimated using follow-up sera from 98 patients (60 with primary infections and 38 with secondary infections) whose first-specimen IgM index was strongly positive, suggesting recent disease onset. Regression analysis of the follow-up IgM index versus days between samples yielded a trend line that reached the cut-point index (1.10) at 179 days for the primary infection group and 139 days for the secondary infection group. This difference reflected significantly higher first-sample IgM indices in primary infections than in secondary infections rather than differences in IgM decay rates.

Fig. 1.

Second-sample IgM index values plotted against the number of days between the first and second samples (range, 1 to 219 days) for 98 patients whose first sample was DV IgM positive with an index of >5.32. The solid line represents the trend line, and the dashed lines parallel to the trend line represent the 95% confidence interval. The horizontal dashed line indicates the IgM index value that discriminates positive from negative (1.10). The legend indicates the number of days until the trend line reached the discriminatory index and also the 95% confidence interval (CI).

Fig. 2.

Data from Fig. 1 segregated into primary and secondary infection groups based on IgM/IgG ratio. The line designations are the same as used in Fig. 1.