Effect of frozen storage on gametocyte mRNA preserved on filter papers. Percentage of mRNA amplification in 10, 1.0 and 0.1 gametocyte/μl dilutions, determined by QT-NASBA (open bars) and RT-PCR (hatched bars), when stored on filter paper. (a) shows the Whatman 903 Protein Saver filter paper, (b) the Whatman FTA Classic Card, and (c) sample stored in guanidine isothiocyanate buffer, when stored under frozen temperatures for up to thirteen weeks. The background blue to pink colour gradient represents the severity of the incubation condition (from cold to warm, respectively). Raw data is shown in Tables S2 and S3, additional files.