title: Prospective evaluation of BDProbeTec strand displacement amplification (SDA) system for diagnosis of tuberculosis in non-respiratory and respiratory samples.
abstract: Nucleic acid amplification techniques (NAATs) have been demonstrated to make significant improvements in the diagnosis of tuberculosis (TB), particularly in the time to diagnosis and the diagnosis of smear-negative TB. The BD ProbeTec strand displacement amplification (SDA) system for the diagnosis of pulmonary and non-pulmonary tuberculosis was evaluated. A total of 689 samples were analysed from patients with clinically suspected TB. Compared with culture, the sensitivity and specificity for pulmonary samples were 98 and 89 %, and against final clinical diagnosis 93 and 92 %, respectively. This assay has undergone limited evaluation for non-respiratory samples and so 331 non-respiratory samples were tested, identifying those specimens that were likely to yield a useful result. These were CSF (n = 104), fine needle aspirates (n = 64) and pus (n = 41). Pleural fluid (n = 47) was identified as a poor specimen. A concern in using the SDA assay was that low-positive samples were difficult to interpret; 7.8 % of specimens fell into this category. Indeed, 64 % of the discrepant results, when compared to final clinical diagnosis, could be assigned as low-positive samples. Specimen type did not predict likelihood of a sample being in the low-positive zone. Although the manufacturers do not describe the concept of a low-positive zone, we have found that it aids clinical diagnosis.
authors.affiliation: Centre for Medical Microbiology, Department of Infection, Royal Free & University College Medical School, Pond Street, London NW3 2PF, UK 2Department of Thoracic Medicine, Royal Free Hospital NHS Trust, Pond Street, London NW3 2PF, UK.
authors.forename: T D
authors.initials: TD
authors.lastname: McHugh
authors.affiliation: Centre for Medical Microbiology, Department of Infection, Royal Free & University College Medical School, Pond Street, London NW3 2PF, UK 2Department of Thoracic Medicine, Royal Free Hospital NHS Trust, Pond Street, London NW3 2PF, UK.
authors.forename: C F
authors.initials: CF
authors.lastname: Pope
authors.affiliation: Centre for Medical Microbiology, Department of Infection, Royal Free & University College Medical School, Pond Street, London NW3 2PF, UK 2Department of Thoracic Medicine, Royal Free Hospital NHS Trust, Pond Street, London NW3 2PF, UK.
authors.forename: C L
authors.initials: CL
authors.lastname: Ling
authors.affiliation: Centre for Medical Microbiology, Department of Infection, Royal Free & University College Medical School, Pond Street, London NW3 2PF, UK 2Department of Thoracic Medicine, Royal Free Hospital NHS Trust, Pond Street, London NW3 2PF, UK.
authors.forename: S
authors.initials: S
authors.lastname: Patel
authors.affiliation: Centre for Medical Microbiology, Department of Infection, Royal Free & University College Medical School, Pond Street, London NW3 2PF, UK 2Department of Thoracic Medicine, Royal Free Hospital NHS Trust, Pond Street, London NW3 2PF, UK.
authors.forename: O J
authors.initials: OJ
authors.lastname: Billington
authors.affiliation: Centre for Medical Microbiology, Department of Infection, Royal Free & University College Medical School, Pond Street, London NW3 2PF, UK 2Department of Thoracic Medicine, Royal Free Hospital NHS Trust, Pond Street, London NW3 2PF, UK.
authors.forename: R D
authors.initials: RD
authors.lastname: Gosling
authors.affiliation: Centre for Medical Microbiology, Department of Infection, Royal Free & University College Medical School, Pond Street, London NW3 2PF, UK 2Department of Thoracic Medicine, Royal Free Hospital NHS Trust, Pond Street, London NW3 2PF, UK.
authors.forename: M C
authors.initials: MC
authors.lastname: Lipman
authors.affiliation: Centre for Medical Microbiology, Department of Infection, Royal Free & University College Medical School, Pond Street, London NW3 2PF, UK 2Department of Thoracic Medicine, Royal Free Hospital NHS Trust, Pond Street, London NW3 2PF, UK.
authors.forename: S H
authors.initials: SH
authors.lastname: Gillespie
mesh_terms: D001202:Ascitic Fluid / Q000382:microbiology; D015373:Bacterial Typing Techniques / Q000379:methods; D002555:Cerebrospinal Fluid / Q000382:microbiology; D005189:False Positive Reactions; D006801:Humans; D008168:Lung / Q000382:microbiology; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification; D021141:Nucleic Acid Amplification Techniques / Q000379:methods*; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013492:Suppuration / Q000382:microbiology; D014376:Tuberculosis / Q000175:diagnosis* / Q000382:microbiology