Larger Lymph Nodes and Pus Samples Boost Rapid TB Test Positivity in Neck Nodes

Researchers have identified which patients with tuberculosis of the neck lymph nodes are most likely to test positive on Xpert MTB/RIF, the rapid molecular test recommended for microbiological testing of lymph node specimens. In a retrospective study of 334 people who underwent ultrasound-guided lymph node sampling, the test came back positive in 231 cases, or 69.2 percent. Two features stood out: larger lymph nodes and pus specimens, both of which substantially raised the odds of a positive result.

The study, published in BMC Infectious Diseases, drew on patients clinically diagnosed with cervical tuberculous lymphadenitis who were sampled at a single center between January 15, 2020, and February 24, 2025. Cervical tuberculous lymphadenitis is an infection of the neck’s lymph nodes by Mycobacterium tuberculosis, and Xpert positivity in this condition may depend on lesion characteristics and the composition of the specimen collected.

Among the positive results, 217 samples indicated rifampin-susceptible tuberculosis, 12 showed rifampin resistance, and 2 were rifampin-indeterminate. The test therefore provided information about rifampin susceptibility from the same sample used to confirm the diagnosis.

To find out which characteristics predicted a positive result, the team analyzed clinical variables, ultrasound findings, and specimen types using univariable and multivariable logistic regression. After adjusting for other factors, two determinants remained independently significant. Lymph nodes measuring at least 1.5 centimeters in diameter were associated with roughly double the odds of Xpert positivity, with an adjusted odds ratio of 2.20 and a 95 percent confidence interval of 1.26 to 3.94 (P = 0.006). Pus specimens carried far stronger weight, with an adjusted odds ratio of 6.38 and a 95 percent confidence interval of 3.39 to 12.83 (P < 0.001).

The raw positivity rates underscored the pattern. Xpert MTB/RIF detected tuberculosis in 81.5 percent of patients whose lymph nodes exceeded 1.5 centimeters. Pus specimens were even more striking, yielding positive results in 90.2 percent of cases.

The authors’ conclusion follows directly from these associations: during ultrasound-guided sampling, liquefactive necrotic areas should be preferentially targeted when they can be safely accessed. The study did not directly test whether such targeting improves detection rates, but the strong link between pus specimens and positive results supports that approach in this cohort.

The findings are grounded in the design of the study itself. As a single-center retrospective analysis, it reflects the patient population, equipment, and sampling practices of one institution, and patients were classified against clinical diagnoses rather than a single microbiological reference standard. The associations describe which sample characteristics accompanied positive tests in this cohort; they do not establish that targeting necrotic areas will raise detection rates in every setting.

Even so, the results give clinicians concrete guidance drawn from real-world practice: when tuberculosis of the neck lymph nodes is suspected and sampling is performed under ultrasound guidance, pus specimens and larger nodes were the characteristics most strongly linked to a positive Xpert MTB/RIF result. With 12 rifampin-resistant detections among the 231 positive cases, the study also illustrates how a single specimen can simultaneously confirm the diagnosis and provide rifampin susceptibility information.

Subject of Research: Clinical and sonographic determinants of Xpert MTB/RIF positivity in cervical tuberculous lymphadenitis

Article Title: Clinical and sonographic determinants of Xpert MTB/RIF positivity in cervical tuberculous lymphadenitis: a retrospective study

Article References: Zhang, W., Chen, P., Tang, W., Zhang, Y., Yu, X., & Wang, C. (2026). Clinical and sonographic determinants of Xpert MTB/RIF positivity in cervical tuberculous lymphadenitis: a retrospective study. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14705-5

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14705-5

Keywords: tuberculosis, Xpert MTB/RIF, cervical lymphadenitis, ultrasound-guided biopsy, rifampin resistance, liquefactive necrosis, pus specimen, retrospective study, Mycobacterium tuberculosis, diagnostic testing, Clinical, sonographic