Likewise, A1AT measurement by enzyme-linked immunosorbent assay (ELISA) in 30 human samples yielded results similar to those obtained by LC-MS/MS; i.e., A1AT had higher levels in diarrheal samples compared with stool from healthy controls; however, among diarrheal samples, A1AT was significantly diminished in those from patients with CDI (Figure 4B and Figure 1D). This evidence concerns the gene SERPINA1 and clostridium difficile infection.