Effects of lyophilization and storage temperature on Wuchereria bancrofti antigen sensitivity and stability

Abstract

Objective: Antigen-based rapid diagnostic tests for Lymphatic filariasis (LF) do not come with external quality control (QC) materials, and research and disease control programmes rely on stored positive samples. This study was undertaken to evaluate the use of lyophilized Wuchereria bancrofti antigen positive plasma samples to serve as QC materials for LF diagnostic tests. 10 well characterized W. bancrofti positive samples were lyophilized and stored at 4, 28 and 40 °C. The samples were evaluated using the Alere Filariasis Test Strips before lyophilization, and after 1 and 3 months of storage. The sensitivity and stability of the lyophilized samples were evaluated.

Results: The results revealed a loss of sensitivity and stability with increasing temperature and duration of storage. The results are further discussed in terms of the use of dried blood spot (DBS) in diagnostic studies on LF, and the need for thoughtful DBS preparation and storage.

Keywords: Dried blood spots; Freeze-drying; Lyophilization; Wuchereria bancrofti antigen.

Fig. 1

Change in antigen stability with temperature and storage time. Error bars represent the standard errors of the mean. * denotes significance compared to baseline (p < 0.01)