Fig. 2

Optical density values across the visible spectrum of light for HtLAMP samples with and without HNB. Between the wavelengths of 550–650 nm higher optical densitometry readings were found for samples that were positive by HtLAMP (no HNB positive and HNB positive). In addition, at these wavelengths, the optical densitometry readings were also able to distinguish samples that were positive due to the presence of the magnesium pyrophosphate precipitate (no HNB positive) and samples that were by positive by HtLAMP due to the blue colour change associated (HNB positive)