## 4 Discussion
### Future Directions for HMMD Adoption  
HMMDs currently produce binary results, leaving reflex culture decisions primarily to clinician judgment. Since the COVID-19 pandemic, molecular diagnostics have become increasingly relied upon in microbiology, but an over-dependence on molecular results alone may pose clinical challenges. Our findings reveal variability in MFI thresholds for _Salmonella_, suggesting that probe MFIs related to different infectivity doses could be interpreted more flexibly.  
This study was conducted on a heterogeneous group of patients, including those with true salmonellosis, convalescents, probable _Salmonella_ carriers, and individuals with other gastrointestinal diseases. While this variability does not meet the strict inclusion and exclusion criteria of formal clinical trials, it reflects real-world diagnostic settings, where patient populations are often diverse. By analyzing this group, we aimed to evaluate the practical challenges associated with HMMDs and binary molecular interpretations, rather than conducting a controlled clinical trial. This approach emphasizes the importance of developing diagnostic frameworks that can address the complexities and uncertainties of molecular diagnostics in clinical practice.  
Continuous monitoring and adjustment of thresholds, such as with the Luminex xTAG GPP assay, alongside efforts like the FDA's TPLC activities, are encouraging developments that enhance the acceptance and reliability of molecular diagnostics. To further improve result interpretation, establishing an \"indeterminate\" category for cases with low MFI values would enable clinicians to combine these results with patient-specific clinical contexts and consider confirmatory cultures where necessary.  
Figure 6: Number of MDR reports by year from June 2019 to April 2024. In September 2019, the FDA’s CDRH reorganized to focus on device oversight across the entire product lifecycle, from design and development to actual use, by implementing TPLC. Since its early implementation in 2019, post-market MDR data collected for the Gastrointestinal Pathogen Panel Multiplex Nucleic Acid-Based Assay System shows that false positive results have remained the most prevalent issue up to recent times.  
As molecular diagnostics continue to advance and NGS integration looms, adopting indeterminate interpretation facilitates more meaningful utilization of diagnostic data. Such an approach would help avoid over-diagnosis and offer a practical model for future NGS data handling, supporting nuanced clinical decision-making and accurate public health reporting.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/diagnostics15010077/s1](https://www.mdpi.com/article/10.3390/diagnostics15010077/s1)]([https://www.mdpi.com/article/10.3390/diagnostics15010077/s1](https://www.mdpi.com/article/10.3390/diagnostics15010077/s1)), Table S1: Comparison of FDA-approved Gastrointestinal Pathogen Panel Multiplex Nucleic Acid-Based Assay Systems.  
Conceptualization, H.K., J.-S.K., K.J.L. and K.U.P.; Formal analysis, H.K.; Investigation, K.U.P.; Resources, H.K., J.-S.K., and K.U.P.; Writing-original draft, H.K.; Writing--review & editing, S.H.S., J.-S.K. and K.U.P.; Visualization, H.K.; Project administration, K.U.P.; Funding acquisition, K.U.P. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the National Institute of Health (NIH) research project (project No. 2024-ER2112-00).  
The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Institutional Review Board of Seoul National University Bundang Hospital (protocol code E-1502-286-303; date of approval: 26 February 2015).  
Patient consent was waived due to the retrospective nature of this study.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors declare no conflicts of interest.