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Despite having a good specificity for tuberculous pleural effusion diagnosis, genotype MTBDRplus line probe assay (MTBDRplus) could not be included in most diagnostic algorithms as a result of its low sensitivity, according to study results published in Infectious Diseases.
In this prospective study conducted at the Aga Khan University in Karachi, Pakistan, researchers evaluated the diagnostic accuracy of MTBDRplus for pleural tuberculosis (TB) diagnosis compared with clinical and microbiologic diagnosis. Pleural fluid from 203 adult patients (mean age, 48.5 years; 64% men), who presented with clinical suspicion of TB and evidence of pleural effusion on a chest radiograph, were collected and tested for smear, culture, and MTBDRplus
Of the 203 pleural fluid samples, 14 (6.9%) were MTBDRplus-positive, 27 (13.3%) were culture-positive, and 4 (1.9%) were smear-positive. A total of 106 patients (27 culture-positive and 79 culture-negative) successfully completed TB treatment with resolution of symptoms, weight gain, and resolution of pleural effusion on chest radiograph.
Considering culture as a gold standard, sensitivity of MTBDRplus was 44.4% (95% CI, 25.5-64.7) and the specificity was 98.9% (95% CI, 95.96-99.9). The sensitivity of MTBDRplus was further reduced to 13.2% (95% CI, 7.4-21.2) when compared with clinical diagnosis but showed a very high specificity of 100% (95% CI, 96.1-100).
The sensitivities of rifampicin and isoniazid were evaluated in all 12 samples positive for both MTBDRplus and culture. Excluding indeterminate results (6/12), MTBDRplus accurately detected isoniazid sensitivity in 5 of 6 and rifampicin sensitivity in 6 of 6 cases.
With positive results, MTBDRplus may be used for rapid diagnosis pending culture results and pleural biopsy where feasible, noted the researchers. “Clinical assessment and correlation remain central to diagnosis and further studies are needed to evaluate new, rapid and more sensitive tests like XpertUltra for the early diagnosis of tuberculous pleural effusion,” investigators concluded.
Reference
Irfan M, Idrees F, Jabeen K, Zubairi ABS, Butt S, Hasan R. Accuracy of genotype MTBDRplus line probe assay in patients with tuberculous pleural effusion: comparison with clinical and culture based diagnosis. Infect Dis. 2019 Dec 4:1-7.
