Importance of Specimen Type and Quality in Diagnosing Middle East Respiratory Syndrome

Huh, Hee Jae; Ko, Jae-Hoon; Kim, Young-Eun; Park, Chang-Hun; Hong, Geehay; Choi, Rihwa; Yu, Shinae; Cho, Sun Young; Kang, Ji-Man; Lee, Myoung-Keun; Ki, Chang-Seok; Kang, Eun-Suk; Lee, Nam Yong; Kim, Jong-Won; Kim, Yae-Jean; Ha, Young Eun; Kang, Cheol-In; Chung, Doo Ryeon; Peck, Kyong Ran; Song, Jae-Hoon

In total, 5,330 MERS-CoV rRT-PCR results from 3,484 individuals were available for analysis, including 4,291 sputums, 145 tracheal aspirates, 732 nasopharyngeal swabs (NPSs), 35 oropharyngeal swabs, 62 nasopharyngeal and oropharyngeal swabs, and 65 other specimens (Table 1) In early phases of the outbreak in the present study, initial diagnostic MERS-CoV rRT-PCR assays were simultaneously conducted by using both sputum and NPS specimens in 36 individuals. From sputum specimens, two, six, and one specimens were positive, equivocal, and indeterminate, respectively. However, only one equivocal result was obtained from NPS specimens. The detection rate for NPS specimens was significantly lower than that for sputum specimens in both upE and ORF1a tests (P = 0.0078 and 0.0156, respectively). The low virus detection rate in NPS specimens early in MERS-CoV infection illustrates the importance of specimen type for diagnosis. It is suggested that URT specimens are not suitable for diagnosing MERS-CoV infections. On the basis of the WHO interim recommendations, LRT specimens are preferred for detecting MERS- CoV RNA, but collection of URT specimens in addition to LRT is recommended whenever possible [2] . US CDC guidelines endorse the collection of LRT, URT, and serum specimen types for testing [10] . Although simultaneous specimen collection is ideal, it is not feasible because of practical limitations during large and complex outbreaks. On the basis of our results, it seems sufficient to obtain LRT specimens prior to URT or other specimens, especially in early-stage diagnostic testing.