Jae-Hyung Lim1, Chang-Ki Kim2, Mi Hyun Bae1. 1. Department of Laboratory Medicine, Hanyang University Guri Hospital, Hanynag University College of Medicine, Guri, Korea. 2. Department of Laboratory Medicine, Seoul Clinical Laboratories, Yongin, Korea.
Abstract
BACKGROUNDS: Rapid discrimination between Mycobacterium tuberculosis (MTB) and nontuberculous mycobacteria (NTM) is critical for patient treatment and to avoid unnecessary expenditure on infection control. Because real-time PCR assays distinguish MTB from NTM, we evaluated the performance of two real-time PCR assays (AdvanSure and PowerChek). METHODS: This study used 143 DNA samples from respiratory specimens which were collected based on routine PCR results using Anyplex kit. A total of 87 positive samples (65 MTB and 22 NTM) and 56 negative samples were collected consecutively during 6 months and 1 month, respectively. The diagnostic performance of PCR assays (AdvanSure and PowerChek) was retrospectively analyzed based on the results of conventional mycobacterial tests and routine PCR assay. RESULTS: Based on culture results, the sensitivities/specificities of AdvanSure and PowerChek were 90.7%/87.6% and 92.6%/85.4%, respectively, for MTB detection. For PCR-positive specimens, the quantification cycle (Cq) values of smear-negative specimens were higher than those of the smear-positive specimens (P < 0.001). As expected, the two PCR assays had the same sensitivities for NTM detection, viz. 90.0%, and their specificities were 99.2% and 98.4%, respectively. The overall agreement rate between the three PCR assays was 96.5% for MTB and 97.9% for NTM. CONCLUSION: The sensitivities of PCR assays in our study might be overestimated, because this study enrolled relatively lower number of PCR-negative samples which potentially missed PCR-negative but culture-positive specimens. However, the two real-time PCR assays for detecting MTB and NTM perform equally well in relative performance evaluation and their Cq values can be considered suitable for predicting smear-positive specimens.
BACKGROUNDS: Rapid discrimination between Mycobacterium tuberculosis (MTB) and nontuberculous mycobacteria (NTM) is critical for patient treatment and to avoid unnecessary expenditure on infection control. Because real-time PCR assays distinguish MTB from NTM, we evaluated the performance of two real-time PCR assays (AdvanSure and PowerChek). METHODS: This study used 143 DNA samples from respiratory specimens which were collected based on routine PCR results using Anyplex kit. A total of 87 positive samples (65 MTB and 22 NTM) and 56 negative samples were collected consecutively during 6 months and 1 month, respectively. The diagnostic performance of PCR assays (AdvanSure and PowerChek) was retrospectively analyzed based on the results of conventional mycobacterial tests and routine PCR assay. RESULTS: Based on culture results, the sensitivities/specificities of AdvanSure and PowerChek were 90.7%/87.6% and 92.6%/85.4%, respectively, for MTB detection. For PCR-positive specimens, the quantification cycle (Cq) values of smear-negative specimens were higher than those of the smear-positive specimens (P < 0.001). As expected, the two PCR assays had the same sensitivities for NTM detection, viz. 90.0%, and their specificities were 99.2% and 98.4%, respectively. The overall agreement rate between the three PCR assays was 96.5% for MTB and 97.9% for NTM. CONCLUSION: The sensitivities of PCR assays in our study might be overestimated, because this study enrolled relatively lower number of PCR-negative samples which potentially missed PCR-negative but culture-positive specimens. However, the two real-time PCR assays for detecting MTB and NTM perform equally well in relative performance evaluation and their Cq values can be considered suitable for predicting smear-positive specimens.
Authors: Robert Blakemore; Pamela Nabeta; Amy L Davidow; Viral Vadwai; Rasim Tahirli; Vanisha Munsamy; Mark Nicol; Martin Jones; David H Persing; Doris Hillemann; Sabine Ruesch-Gerdes; Felicity Leisegang; Carlos Zamudio; Camilla Rodrigues; Catharina C Boehme; Mark D Perkins; David Alland Journal: Am J Respir Crit Care Med Date: 2011-11-01 Impact factor: 21.405
Authors: Sven O Friedrich; Andrea Rachow; Elmar Saathoff; Kasha Singh; Chacha D Mangu; Rodney Dawson; Patrick Pj Phillips; Amour Venter; Anna Bateson; Catharina C Boehme; Norbert Heinrich; Robert D Hunt; Martin J Boeree; Alimuddin Zumla; Timothy D McHugh; Stephen H Gillespie; Andreas H Diacon; Michael Hoelscher Journal: Lancet Respir Med Date: 2013-07-01 Impact factor: 30.700