Performance Comparison of GeneXpert MTB/RIF and ProbeTec ET Tests for Rapid Molecular Diagnosis of Extrapulmonary Tuberculosis in a Low TB/MDR-TB Incidence Country.

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Performance Comparison of GeneXpert MTB/RIF and ProbeTec ET Tests for Rapid Molecular Diagnosis of Extrapulmonary Tuberculosis in a Low TB/MDR-TB Incidence Country.

Med Princ Pract. 2021 Feb 16;:

Authors: Mokaddas E, Ahmad S, Eldeen H

Abstract
OBJECTIVE: Early detection and effective treatment are essential for global tuberculosis control. This study evaluated the performance of GeneXpert MTB/RIF (Xpert) and ProbeTec ET (PTec-ET) assays in diagnosing extrapulmonary tuberculosis (EPTB) in Kuwait.
MATERIALS AND METHODS: Nonrespiratory clinical specimens (n=3995) collected from 3995 patients suspected to have EPTB were tested. These included cavitary fluids (n=2054), fine needle aspirate (FNA)/pus/tissue biopsy (n=1461), urine (n=302), cerebrospinal fluid (CSF, n=118), and others (n=60). All specimens were processed for acid-fast bacilli (AFB), culture in MGIT 960 system and nucleic acid detection by Xpert and PTec-ET according to manufacturer's instructions.
RESULTS: Of 3995 specimens, 95 were AFB-positive, 403 were culture-positive and an additional 86 samples had histopathology suggestive of TB. Using culture as reference, the sensitivity and specificity values were 88.33% and 97.3% for Xpert and 72.95% and 97.80% for PTec-ET, respectively. Although performance of both tests was comparable in AFB-positive samples, Xpert detected significantly more cases in culture-positive samples. Among culture-negative samples, Xpert detected 18 more cases including 16 with histopathological evidence of TB. Lowest positivity was detected for both tests in cavitary fluids. Xpert performed better than PTec-ET in culture-positive FNA/pus/tissue biopsy and CSF samples.
CONCLUSIONS: Although performance of both tests was suboptimal for AFB-negative/culture-positive samples, Xpert performed better than PTec-ET and also detected more cases of AFB-negative/culture-nagative/histopathology-positive samples. PTec-ET was positive in three while Xpert was positive in all six culture-positive CSF specimens for rapid diagnosis of TB meningitis. Xpert was thus superior to PTec-ET or smear microscopy in rapidly diagnosing EPTB.

PMID: 33592621 [PubMed - as supplied by publisher]