Diagnostic utility of Xpert MTB/RIF ultra in clinically suspected tuberculous lymphadenitis in low-burden settings: a single center experience from Saudi Arabia.

BACKGROUND

Tuberculosis (TB) is a major global health issue, particularly among HIV-positive individuals. In Saudi Arabia, the incidence has declined to 8.4 per 100,000 but remains a concern among high-risk groups. Extrapulmonary TB, especially tuberculous lymphadenitis (TBL), is challenging to diagnose due to the low sensitivity of smear, culture, and histopathology. Xpert MTB/RIF Ultra (Xpert-Ultra) offers improved detection in paucibacillary disease, though local evidence remains limited.

METHOD: We retrospectively reviewed 85 adult patients with suspected TBL at King Abdulaziz Medical City, Riyadh (2012-2024). Clinical, radiological, histopathological, and microbiological data were collected. The sensitivity of Xpert-Ultra, GeneXpert, and ProbTec was assessed against a composite reference standard comprising confirmed and presumed TB cases.

RESULT: Among 85 patients, the majority were males (55.3%) and Saudi nationals (91.8%), with most aged 41-65 years (36.5%). Cervical lymphadenopathy was the most common presentation (64.7%). Necrotizing granulomas were observed in 78.8% of biopsies. Culture was positive in 43.6% (17/39), while AFB staining was detected in 14.8% (12/81). Overall, PCR sensitivity was 38.8% (33/85). Xpert-Ultra achieved higher sensitivity (41.3%) compared with GeneXpert (31.6%) and ProbTec (33.3%). Xpert-Ultra missed two culture-positive cases but detected three culture-negative ones. PCR positivity was associated with extensive lymph node involvement and culture positivity.

CONCLUSION

Xpert-Ultra outperformed older molecular assays but remained insufficient as a standalone diagnostic tool for TBL. Its complementary role alongside histopathology and culture supports its integration into diagnostic pathways, potentially improving time to initiation of treatment.