## 1 Introduction
However, HMMDs face several challenges, such as the uncertain clinical significance of some targets (e.g., Enteropathogenic _Escherichia coli_), the potential for multiple positive analytes in a single specimen, and the inability to distinguish between viable and non-viable cells. Additionally, HMMDs lack susceptibility information, may render specimens incompatible with culture-based tests, and do not provide culture results, which complicates public health efforts to obtain comprehensive infection-related data [8]. The sensitivity and specificity of HMMDs are critical factors for their effective public health application [9]. Therefore, the CDC recommends reflex culturing of specimens with positive HMMD results to enhance infection surveillance [10]. \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline \multirow{3}{*}{**Device Name**} & **BIOFIRE** & \multirow{3}{*}{**VERIGENE**} & \multirow{3}{*}{**xTAG Gastrointestinal-**} & **BD MAX** & \multirow{3}{*}{**QIAstat-Dx**} & **Biocode Gas-** \\  & **FILMARRAY** & & **Enteric Pathogen** & & **tesinal** \\  & **nal Panel** & **Nucleic Acid Test** & **Pathogen Panel** & **Bacterial Panel** & & **nal Panel 2** \\ \hline \multirow{3}{*}{Company} & BioFire & \multirow{3}{*}{Nanosphere, Inc.} & \multirow{3}{*}{20 June 2014} & \multirow{3}{*}{20 June 2013} & \multirow{3}{*}{20 May 2017} & \multirow{3}{*}{31 May 2024} & \multirow{3}{*}{28 September 2018} \\  & Diagnostics, LLC & & & & & & \\ \cline{1-1}  & & & & & & \\ \cline{1-1}  & First FDA & & & & & & \\ \cline{1-1}  & Approval & 2 May 2014 & 20 June 2014 & 21 March 2013 & 2 May 2017 & 31 May 2024 & 28 September 2018 \\ \cline{1-1}  & Time to Result & \(\sim\)1 h & \(\sim\)2 h & 5 h & \(\sim\)3 h & \(\sim\)1 h & \(<\)5 h \\ \cline{1-1}  & 22 & 9 & 15 & 6 & 16 & 18 \\ \cline{1-1}  & (13 bacteria, & (5 bacteria, & (9 bacteria, & (4 bacteria and & (8 bacteria, & (12 bacteria, \\ \cline{1-1}  & 5 viruses, and & 2 viruses, and & 3 viruses, and & 2 toxins) & 4 viruses, and & 3 viruses, and \\ \cline{1-1}  & 4 parasites) & 2 toxins) & 3 parasites) & 3 parasites) & 4 parasites) & 3 parasites) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of FDA-approved Gastrointestinal Pathogen Panel Multiplex Nucleic Acid-Based Assay Systems. The first FDA-approved HMMD, the Luminex xTAG Gastrointestinal Pathogen Panel (GPP), employs nucleic acid amplification technology to simultaneously detect multiple targets from a single patient specimen. This technology combines PCR with bead-based multiplexing. Each target is assessed using specific mean fluorescence intensity (MFI) thresholds, although the rationale for these thresholds has not been extensively documented. For _Salmonella_ detection, the Luminex xTAG GPP uses two probes with defined MFI thresholds. Probe 1, the primary probe, indicates positivity with an MFI above 1400 and negativity with an MFI below 200, while intermediate values (200-1400) are evaluated using probe 2. Probe 2 is set with an MFI threshold of 200 for positivity and below 200 for negativity. On 12 November 2019, the thresholds for _Salmonella_ detection were revised, with probe 1's threshold updated to 300 for negative, 100,000 for positive, and 300-100,000 for reflex to probe 2. This update aimed to enhance the stringency of positive calls and reduce false positives based on customer feedback. However, the impact of this revision on actual _Salmonella_ detection has not been thoroughly reported. This study aims to investigate the limitations of binary molecular interpretations in clinical microbiology by evaluating the impact of changes in the MFI cutoff on _Salmonella_-positive results using the Luminex xTAG GPP. Beyond assessing these technical adjustments, the study proposes the introduction of an \"indeterminate\" category for borderline molecular results, addressing the diagnostic gaps inherent in the current binary approach.