Laboratory-Negative Results as a Marker of Diagnostic Gap: A Retrospective Study in the One Health Context

Background: Antimicrobial resistance (AMR) is a major global health concern, driven in part by inappropriate antimicrobial use and diagnostic uncertainty. Laboratory-based diagnostics play a critical role in guiding rational therapy; however, a high proportion of laboratory-negative results may reflect potential gaps in diagnostic processes. Objective: The objective of this study is to assess the proportion of laboratory-confirmed infections among patients undergoing microbiological investigations and to explore a potential diagnostic gap using laboratory-negative results as an indirect and exploratory indicator. Methods: This retrospective cross-sectional study was conducted in the Department of Microbiology of a tertiary care teaching hospital. A total of 1,304 microbiological samples, including serological, bacteriological, and mycological investigations, were analyzed. Data were extracted from laboratory records, and variables such as age, sex, department (OPD/IPD), type of investigation, and laboratory results were assessed. Positivity rates were compared across diagnostic modalities. Statistical analysis was performed using the chi-square test, with a p-value of <0.05 considered statistically significant. Results: Serological investigations constituted the majority of samples (86.4%). The overall laboratory positivity rate was 19.9%, with 80.1% of samples showing no confirmed infection. Bacteriological investigations demonstrated a higher positivity rate (59.2%) compared to serology and mycology. Positivity rates varied across age groups, with higher rates observed among elderly patients. Modality-specific differences in diagnostic yield were observed, suggesting variability in test utilization patterns. Conclusion: This study demonstrates a high proportion of laboratory-negative results, indicating a potential diagnostic gap in clinical practice. These findings should be interpreted cautiously due to the influence of pre-analytical factors, analytical limitations, and variations in test utilization. Strengthening diagnostic stewardship and promoting microbiology-guided therapy are essential to optimize antimicrobial use. The results are interpreted within a one health perspective as a conceptual framework. Further prospective studies incorporating clinical correlation and antimicrobial exposure are required.