For best results, we recommend using extracted nucleic acid. Because colorimetric LAMP reactions change color based on a pH change during amplification, the nucleic acid should be eluted or prepared in water to avoid carrying over excess buffer into the reaction. Material eluted in TE or similar elution buffer should be kept to less than 5 μl (20% v/v) of the final reaction volume. Up to 1 µl (4% v/v) of transport media (UTM or VTM) may be used without impacting the colorimetric reaction. To increase sample volume, use 0.1X Elution Buffer or water for preparation of the nucleic acid. Note that SDS is typically not tolerated well in colorimetric LAMP and guanidine compounds (hydrochloride, isothiocyanate) should be kept to less than 60 mM in the final reaction.
Simple and/or crude sample prep methods are being developed in an ongoing basis and some of these are also compatible with colorimetric LAMP. MedRXiv and BioRXiv are good resources for the most up-to-date options regarding sample prep. A selection of preprints describing different sample types and their utility with colorimetric LAMP can be found on the Isothermal Amplification, RT-qPCR, and COVID-19 page.