A semi-quantitative rapid multi-range gradient lateral flow immunoassay for procalcitonin

A rapid semi-quantitative gradient lateral flow immunoassay (LFIA) of procalcitonin (PCT), a peptide precursor of the hormone calcitonin, was developed. The method is based on particular analyte cut-offs by immobilizing specific antibodies on the test strip with a consistent (gradient) increase in concentration from line to line. Semi-quantitative multi-range analysis is evaluated visually by counting the number of colored test lines corresponding to a certain concentration range of sepsis marker: [PCT]?0.25; 0.25[PCT]<0.5; 0.5[PCT]<2; 2[PCT]<10; [PCT]10ngmL(-1). This multi-range gradient LFIA was implemented by using two types of label: spherical gold nanoparticles (35nm) and hierarchical popcorn-like gold nanoparticles (100nm). The comparison of this LFIA with an ELISA (for n=82) yielded 87.5% and 76.6% sensitivities, and 92.3% and 92.3% specificities, respectively. Thus, multi-range gradient LFIA performs well at PCT thresholds, which is important for early diagnosis of sepsis and severe bacterial infection. In our perception, this method has a wide scope in that it may be implemented in numerous other LFIA based test systems.