Sinus tract presence and documented microbiological positivity in chronic osteomyelitis: a Northwest China cohort

Background Microbiological documentation is essential for targeted antimicrobial therapy in chronic osteomyelitis, yet the probability of a documented positive result may vary across clinical phenotypes and sampling practice. We characterized the recorded microbiological spectrum of chronic osteomyelitis in Kashi, Northwest China, and evaluated clinical factors associated with documented microbiological positivity in routine hospital records. Methods This retrospective record-based cohort study used routinely collected hospital records from The First People’s Hospital of Kashi from 2012 to 2019. The primary outcome was documented microbiological positivity, defined by a positive microbiological-result code (PN = 1). Negative (PN = 2) and other or uncertain (PN = 3) results were classified as no documented positivity. Adjusted prevalence ratios (aPRs) were estimated with modified Poisson regression and patient-cluster robust standard errors. Results Among 303 eligible records, the median age was 33 years (interquartile range, 20-47.5); 215 (71.0%) involved male patients, 282 (93.1%) Uyghur patients, and 266 (87.8%) rural residents; and 247 (81.5%) had a sinus tract. Documented microbiological positivity occurred in 214 records (70.6%). In the complete-case main model (N = 302), sinus tract presence was independently associated with documented microbiological positivity (aPR, 1.82; 95% confidence interval [CI], 1.30-2.54; P<0.001). Standardized adjusted probabilities were 76.5% with a sinus tract and 44.8% without one, an adjusted difference of 31.8 percentage points (bootstrap 95% CI, 16.0-47.5). The association remained directionally consistent across prespecified sensitivity analyses. Among positive records, Staphylococcus aureus (including methicillin-resistant S. aureus) was recorded in 134 (62.6%), at least one Gram-negative organism in 75 (35.0%), and polymicrobial infection in 30 (14.0%); leading Gram-negative organisms were Escherichia coli (11.2%) and Pseudomonas aeruginosa (9.8%). In the traumatic osteomyelitis subgroup, open injury was not independently associated with positivity (aPR, 1.10; 95% CI, 0.91-1.32). Conclusion In this regional record-based cohort, sinus tract presence was associated with a higher probability of documented microbiological positivity. Because specimen source and sampling intensity were not captured, these findings support active efforts to obtain microbiological confirmation but do not validate sinus-tract specimens as substitutes for standardized deep bone or operative tissue sampling.