[Investigation of the Presence of Mycobacterium tuberculosis Complex DNA in Stool by PCR Method in Patients with...

Sputum is the most commonly used sample in the diagnosis of pulmonary tuberculosis. However, elderly patients, human immunodeficiency virus (HIV) positive patients, patients with neurological deficits and children may not be able to remove sputum easily even if they can produce. Although different samples can be taken with invasive methods in patient groups who cannot expectorate, this situation is both traumatic and costly for the patient. It has been recommended to use stool samples in children and adolescents as a diagnostic sample in pulmonary tuberculosis by using the polymerase chain reaction (PCR) method with Xpert MTB/RIF Ultra by the World Health Organization since 2022. In our study, we aimed to evaluate the potential use of stool samples in adult patients in the diagnosis of pulmonary tuberculosis. Seventeen patients with a pre-diagnosis of tuberculosis who attended the pulmonology clinic of Gaziantep University Şahinbey Research and Application Hospital and 20 volunteers (control group) without tuberculosis symptoms were included in the study. Sputum and stool samples were collected from patients and volunteers. Sputum samples were evaluated by acid-resistant bacilli (AFB) smear microscopy, culture and Xpert MTB/RIF Ultra and stool samples were evaluated only by PCR method with Xpert MTB/RIF Ultra. AFB smear microscopy, sputum culture, sputum and stool samples PCR results of the control group were all found to be negative. The sputum samples PCR results were found positive in the entire patient group. Forty seven percent (n= 8) of the patients were evaluated as AFB smear microscopy positive, while 100% (n= 17) were evaluated as the sputum culture result positive. The stool samples PCR results were found to be positive in 94% (n= 16) of the patients. Although the sputum sample PCR and culture results of one patient were positive, the stool sample PCR result was found to be negative. When the sputum culture result was considered as a reference, the sensitivity of the stool samples PCR test was 94.1%, specificity was 100%, positive predictive value was 100% and negative predictive value was 95.2%. According to the data obtained in our study, the stool sample may be an alternative sample for the diagnosis of pulmonary tuberculosis in elderly, HIV-positive/immunosuppressive patients and in patients with neurological deficits who cannot provide a sputum sample or do not have sufficient sputum production.