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Article Type

Article

Subject Area

Clinical and Chemical Pathology

Abstract

Background Tuberculosis (TB) is a destructive pulmonary disease, which was the most fatal infectious disease in the world for many years before the COVID-19 outbreak. During pandemic, COVID-19 was the main concern in every clinic and there were overlapping respiratory diseases resulting in delaying of the diagnosis and treatment of TB. Xpert MTB/RIF assay and Ziehl–Neelsen (ZN) stain are the most commonly used point-of-care test (POCT) assays for TB that were endorsed by WHO allowing a quick treatment turnaround time of a few minutes or hours, hence avoiding patient loss to follow-up. The aim of the study was to evaluate the role of Xpert MTB/RIF as a POCT for early, rapid, and accurate diagnosis of pulmonary and extrapulmonary TB during the COVID-19 pandemic and its role for exclusion of non-mycobacterial TB infections and to evaluate the proportion of patients with active pulmonary TB among COVID-19 patients and to study the difference of some inflammatory markers between patients with COVID-19, patients with pulmonary TB, and patients infected by both TB and COVID-19. Patients and methods This study was conducted from February 2018 to December 2021 (including the peak period of COVID-19 on 835 suspected TB patients (629 + 206 suspected COVID-19 patients six of them were proved pulmonary TB). Patients were from Shebin El-Kom Teaching Hospital and Chest hospital, Menoufiya). All 835 (pulmonary and extrapulmonary samples) patients were tested by gene Xpert MTB/RIF including 441 of them tested by ZN only. For detection of sensitivity, specificity positive predictive value (PPV), negative predictive value (NPV), and accuracy we selected 103 samples who were tested by the three methods (gene Xpert MTB/RIF, ZN staining, and culture on LJ media). For studying the difference of some inflammatory markers between patients with COVID-19, patients with pulmonary TB, and patients infected by both TB and COVID-19, 206 patients who were suspected of comorbid TB and COVID-19 during the pandemic were divided into three groups: group I positive for TB and COVID-19 (N = 6), group II positive COVID-19 only (N = 100), and group III were positive pulmonary TB only (N = 50) (NB: 50 patients were excluded due to incomplete data). Blood samples were taken for complete blood count, erythrocyte sedimentation rate, malondialdehyde, interleukin-6, C-reactive protein, D-dimer, ferritin, lactate dehydrogenase, calprotectin, and procalcitonin. Nasal swabs were needed for confirmation of COVID-19 by PCR. Results Compared with culture as a gold standard, sensitivity, specificity, PPV, and NPV for ZN smear were 77.1, 100, 100, and 53.8%, respectively. As regards the results of XPERT MTB/RIF assay, from the 103 samples examined, 89 (86%) were positive and 14 (14%) were negative. Eight false-positive results were recorded, compared with culture. The sensitivity was 98.8%, specificity was 61.9%, PPV was 91%, and NPV was 92.8%. There was a significant increase within groups in MDA, procalcitonin, ESR, and calprotectin with P value of 0.22, 0.015, 0.000, and 0.009, respectively. Conclusion Xpert MTB/RIF as POCT for TB diagnosis is more sensitive and specific than traditional methods of diagnosis using ZN to overcome the challenges with weak testing infrastructure especially during the COVID-19 pandemic. Serum calprotectin was significantly increased in the COVID-19 group compared with the TB group C-reactive protein, which was significantly increased in the TB group compared with COVID-19 group.

Keywords

Calprotectin, COVID-19, CRP, D-dimer, LJ, PCT, POCT, pulmonary and extrapulmonary TB, XPERT MTB/RIF, ZN

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