How accurate is diagnosis of cervical TB lymphadenitis utilizing the GeneXpert MTB/RIF assay in HIV-infected patients with palpable cervical lymph nodes?
Background: HIV infection is the most common risk factor associated with extrapulmonary TB (EPTB), with cervical tuberculosis (TB) lymphadenitis the most common manifestation. Automated liquid culture is gold standard for TB diagnosis, but it is labor intensive. In 2010, the WHO endorsed the GeneXpert MTB/RIF assay for pulmonary TB diagnosis in HIV-infected patients from developing countries.
Explore this issue:June 2014
Study design: Prospective, diagnostic test study of 68 consecutive patients aged 16 years old and older with cervical lymphadenopathy between January 2011 and March 2013.
Setting: Center for Research in Infectious Diseases at the National Institute of Respiratory Diseases, Mexico City.
Synopsis: The median patient age was 29 years, and 88.2% of the patients were men. The median CD4 T-cell count was 226.5 CD4 T cells/mm3, and 31 patients were receiving antiretroviral therapy at study enrollment. Fifteen patients had a positive culture for mycobacterium tuberculosis (MTB) and a positive GeneXpert test result. Of those, 12 patients were positive for Ziehl-Neelsen (ZN) staining and three patients were negative. Fifty-three patients had a negative culture for MTB and a negative GeneXpert test result. Compared with the reference standard, GeneXpert correctly identified 15 out of 15 TB cases. GeneXpert was negative in 53 cases, all with negative cultures. Both the positive and negative predictive values were 100%, and the MTB active disease prevalence was 22.05%. Sensitivity and specificity were higher with GeneXpert than with direct visualization on ZN staining. No indeterminate (invalid or error) test results were obtained with GeneXpert. Limitations included a limited sample size, the inability to assess rifampicin resistance detection, and possible bias due to a referral center location.
Bottom line: The study indicates that GeneXpert is useful for cervical TB lymphadenitis diagnosis in HIV-infected patients, regardless of the bacillary load in smear-positive samples or the CD4 T-cell count.
Citation: Ablanedo-Terrazas Y, Alvarado-de la Barrera C, Hernandez-Juan R, Ruiz-Cruz M, Reyes-Teran G. Xpert MTB/RIF for diagnosis of tuberculous cervical lymphadenitis in HIV-infected patients. Laryngoscope. 2014;124:1382-1385.