A three-phase epidemiological fluctuation framework of extrapulmonary tuberculosis in Fuyang, China: a retrospective...

This study characterized eight-year epidemiological and clinical features, diagnostic performance, and drug resistance of EPTB in Fuyang, China, and proposed a framework to interpret its dynamic burden.

We conducted a retrospective study of EPTB patients at Fuyang Second People's Hospital from January 2018 to December 2025. Demographic, clinical, and laboratory data were extracted from medical records. Descriptive statistics and chi-square tests were used to analyze epidemiological characteristics. Diagnostic yields of IGRA, GeneXpert MTB/RIF Ultra, and culture were compared based on positivity rates. Drug susceptibility testing (DST) was performed on culture-positive isolates. MDR was defined as resistance to at least isoniazid and rifampicin.

EPTB accounted for 28.46% (2,281/8015) of all tuberculosis (TB) cases. The majority of patients were aged (≥50 years, 52.78%), male (70.45%), and farmers (70.50%). Temporal analysis revealed a distinctive fluctuation pattern, with EPTB cases predominantly concentrated in 2019-2021 and 2024, which we interpret as reflecting a three-phase fluctuation framework. The most prevalent subtypes of EPTB were pleural TB (60.50%), osteoarticular TB (12.98%), lymphatic TB (6.97%), central nervous system (4.65%), and gastrointestinal TB (3.24%). IGRA showed the highest positivity rate (88.04%), significantly higher than GeneXpert MTB/RIF Ultra (35.60%) and culture (14.53%) (p < 0.001). Clinical characteristics differed across the five most common EPTB subtypes. Among the 54 isolates that underwent DST, resistance rates were highest for isoniazid (14.81%) and ethambutol (11.11%). Overall, 83.33% of these tested isolates were fully susceptible, while 9.26% were multidrugresistant (MDR), accounting for 55.60% of all resistant cases within this tested subset.

EPTB constitutes a significant burden, particularly among aged, male, and farming populations. Pleural TB is the most common form, and IGRA offers superior detection yield. Notably, the 2018-2025 EPTB proportion fluctuations fit a three-phase descriptive framework (diagnosis-driven ascendancy, pandemic disruption, re-equilibration), inspired by Omran's theory as a heuristic analogy, with breakpoints based on annual trends rather than statistically derived. Although overall drug resistance was low among the tested isolates, the presence of MDR cases in this selected sample underscores the importance of routine DST; however, larger unselected studies are warranted to validate the true population-level MDR burden.