en Pulmonary Disease Pulmonary Disease Original Research: Clinical Science Original Research: Clinical Science <strong>Background: </strong>Cystic Fibrosis (CF) is a life-threatening autosomal recessive disease. The purpose of this study was to evaluate the value of Polymerase Chain Reaction (PCR) in CF patients with Nontuberculous Mycobacteria (NTM) negative sputum culture.<br> &nbsp;&nbsp; <strong>Methods:</strong> This is a descriptive cross-sectional study. The population included all children with CF, aged between 5 - 18 years old, with an NTM negative sputum culture. The patient&#39;s sputum samples were sent for smear and culture of NTM, RFLP PCR, and PCR sequence.<br> &nbsp;&nbsp; <strong>Results:</strong> In total, 57 CF patients with negative NTM sputum culture were enrolled. Nine patients (15.78%) had positive sputum PCR for NTM. Among these strains, Mycobacterium simiae was the most common one with 5 cases (8.77% of total positive cases).<br> &nbsp;&nbsp; <strong>Conclusion:</strong> PCR can be used as an alternative diagnostic method for NTM in CF patients with negative NTM sputum culture, always under clinical suspicion of the disease.<br> &nbsp;<span dir="RTL"></span> Cystic Fibrosis, Nontuberculous Mycobacteria, Polymerase Chain Reaction, Sputum 61 64 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-5620-2&slc_lang=en&sid=1 Seyed Hossein Mirlohi sh.mirlohi2004@gmail.com 200319475328460068202 200319475328460068202 No Pediatric Respiratory and Sleep Medicine Research Center, Children’s Medical Center, Tehran University of Medical Sciences, Tehran, Iran Kambiz Eftekhari dr_k_eftekhary@yahoo.com 200319475328460068203 200319475328460068203 No Pediatric Gastroenterology and Hepatology Research Center, Department of Pediatrics, Bahrami Children’s Hospital, Tehran University of Medical Sciences, Tehran, Iran Rohola Shirzadi shirzadi123@yahoo.com 200319475328460068204 200319475328460068204 No Pediatric Respiratory and Sleep Medicine Research Center, Children’s Medical Center, Tehran University of Medical Sciences, Tehran, Iran Abolfazl Fateh afateh2@gmail.com 200319475328460068205 200319475328460068205 No Department of Mycobacteriology and Pulmonary Research, Microbiology Research Center (MRC), Pasteur Institute of Iran, Tehran, Iran Morteza Masoumi mortezamasoumi46@yahoo.com 200319475328460068206 200319475328460068206 No Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran Mohammadreza Modaresi modaresipul@gmail.com 200319475328460068207 200319475328460068207 Yes Pediatric Respiratory and Sleep Medicine Research Center, Children’s Medical Center, Tehran University of Medical Sciences, Tehran, Iran