Enhancing colorimetric loop-mediated isothermal amplification speed and sensitivity with guanidine chloride

Biotechniques. 2020 Sep;69(3):178-185. doi: 10.2144/btn-2020-0078. Epub 2020 Jul 8.


Loop-mediated isothermal amplification (LAMP) is a versatile technique for detection of target DNA and RNA, enabling rapid molecular diagnostic assays with minimal equipment. The global SARS-CoV-2 pandemic has presented an urgent need for new and better diagnostic methods, with colorimetric LAMP utilized in numerous studies for SARS-CoV-2 detection. However, the sensitivity of colorimetric LAMP in early reports has been below that of the standard RT-qPCR tests, and we sought to improve performance. Here we report the use of guanidine hydrochloride and combined primer sets to increase speed and sensitivity in colorimetric LAMP, bringing this simple method up to the standards of sophisticated techniques and enabling accurate, high-throughput diagnostics.

Keywords: LAMP; PCR; SARS-CoV-2; high-throughput screening; isothermal amplification; molecular diagnostics.

MeSH terms

  • Betacoronavirus / isolation & purification*
  • COVID-19 Testing
  • Clinical Laboratory Techniques / methods*
  • Clinical Laboratory Techniques / standards
  • Colorimetry
  • Coronavirus Infections / diagnosis
  • Guanidine*
  • Humans
  • Molecular Diagnostic Techniques / methods*
  • Molecular Diagnostic Techniques / standards
  • Nucleic Acid Amplification Techniques / methods*
  • Nucleic Acid Amplification Techniques / standards
  • Phenolsulfonphthalein
  • SARS-CoV-2


  • Phenolsulfonphthalein
  • Guanidine

Supplementary concepts

  • LAMP assay