title: Comparison of Xpert MTB/RIF Assay and the Conventional Sputum Microscopy in Detecting Mycobacterium tuberculosis in Northern Thailand.
abstract: Background. Despite low sensitivity in detection of Mycobacterium tuberculosis, sputum acid-fast smear remains the main diagnostic method. This study aimed to compare the diagnostic performance of Xpert MTB/RIF assay versus conventional sputum acid-fast smear. Materials and Methods. A cross-sectional study was conducted at Chiang Mai University Hospital, Thailand. Patients who were ≥15 years old and had clinically suspected pulmonary tuberculosis were included. Results. 109 specimens from 57 patients were included. Using MGIT sputum culture as a reference standard, the sensitivity (SEN) and specificity (SPEC) for Xpert were 95.3% (95% CI, 84.2%, 99.4%) and 86.4% (95% CI, 75.7%, 93.6%). The SEN and SPEC for sputum acid-fast smear were 60.5% (95% CI, 44.4%, 75.0%) and 98.5% (95% CI, 91.8%, 100%). Xpert had significantly higher sensitivity (p value < 0.001) and lower specificity (p value = 0.022) than sputum acid-fast smear. Among 43 culture-proven M. tuberculosis specimens, sensitivity of Xpert was 100% (95% CI, 86.7%, 100%) in acid-fast positive smears (n = 26) and 88.2% (95% CI, 63.5%, 98.5%) in acid-fast negative smears (n = 17). Conclusions. The good sensitivity and specificity of Xpert assay in detecting M. tuberculosis from sputum specimens may help in early diagnosis and treatment of pulmonary tuberculosis, particularly among patients who had acid-fast negative sputum smear.
authors.affiliation: Department of Medicine, Faculty of Medicine, Chiang Mai University, Muang, Chiang Mai 50200, Thailand.
authors.forename: Kanokwan
authors.initials: K
authors.lastname: Pinyopornpanish
authors.affiliation: Department of Medicine, Faculty of Medicine, Chiang Mai University, Muang, Chiang Mai 50200, Thailand.
authors.forename: Romanee
authors.initials: R
authors.lastname: Chaiwarith
authors.affiliation: Research Institute for Health Sciences, Faculty of Medicine, Chiang Mai University, Muang, Chiang Mai 50200, Thailand.
authors.forename: Chansom
authors.initials: C
authors.lastname: Pantip
authors.affiliation: Research Institute for Health Sciences, Faculty of Medicine, Chiang Mai University, Muang, Chiang Mai 50200, Thailand.
authors.forename: Rassamee
authors.initials: R
authors.lastname: Keawvichit
authors.affiliation: Research Institute for Health Sciences, Faculty of Medicine, Chiang Mai University, Muang, Chiang Mai 50200, Thailand.
authors.forename: Kanlaya
authors.initials: K
authors.lastname: Wongworapat
authors.affiliation: Central Diagnostic Laboratory, Chiang Mai University Hospital, Muang, Chiang Mai 50200, Thailand.
authors.forename: Phadungkiat
authors.initials: P
authors.lastname: Khamnoi
authors.affiliation: Department of Medicine, Faculty of Medicine, Chiang Mai University, Muang, Chiang Mai 50200, Thailand ; Research Institute for Health Sciences, Faculty of Medicine, Chiang Mai University, Muang, Chiang Mai 50200, Thailand.
authors.forename: Khuanchai
authors.initials: K
authors.lastname: Supparatpinyo
authors.affiliation: Research Institute for Health Sciences, Faculty of Medicine, Chiang Mai University, Muang, Chiang Mai 50200, Thailand.
authors.forename: Thira
authors.initials: T
authors.lastname: Sirisanthana