There are several ways to make LAMP products insoluble besides addition of a cationic polymer like PEI. We tried carrying out the BF separation using chilled ethanol. Since the addition of chilled ethanol lowered the temperature of the LAMP solution, there was a strong tendency for nonspecific probes to weakly hybridize to LAMP products and precipitate (data not shown). Moreover, isopropanol and PEG are believed to be inferior to a PEI solution because it is necessary to add several times the amount of LAMP reaction solution and they are not as easy to handle. Therefore, we believe that low-molecular-weight PEI, which is efficiently insolubilizes amplicons with only a small amount, is the best option for high BF separation, as was shown in this study.