Acute respiratory tract infections (ARTIs) are a leading cause of morbidity and mortality worldwide. Although ARTIs are usually more severe in children, the elderly and immunocompromised patients, as well as individuals from all populations and age groups are susceptible. These infections have a significant impact on medical office and emergency department (ED) visits, antimicrobial prescriptions, hospitalizations, and lost time from work and school. ARTIs are further classified into acute upper respiratory tract infection (URTI), acute bronchitis, or pneumonia. The diagnosis of ARTIs except pneumonia is largely based on clinical signs and symptoms, because viruses—the most common causative pathogens of URTI and acute bronchitis—are difficult to detect. Antibiotics have been prescribed in many patients with URTI or acute bronchitis. Nevertheless, the inappropriate prescription of antibiotics promotes antibiotic resistance. Therefore, these viruses should be detected, preferably by using rapid antigen determination tests. However, the sensitivity of these tests is relatively low.
To improve the sensitivity in detecting these viruses, the nucleic acid amplification test (NAAT) can be used. The NAAT has been developed for various viruses and could detect multiple targets. Despite these advantages, the use of the NAAT has been infrequent because of its complicated procedures and difficulty in performing it at community hospitals. In the past few years, several fully automated platforms for the NAAT have been developed. These platforms allow for simple testing, provide rapid results, and can be used as assays for detecting multiple organisms in a single sample. One of the representative devices, the FilmArray® Respiratory Panel (RP), targets 19 organisms, including adenovirus; influenza A viruses H1, 2009H1, H3 (FluA-H1, FluA-2009H1, and FluA-H3, respectively), and FluB; parainfluenza virus types 1 to 4 (Para 1–4); coronaviruses 229E, HKU1, OC43, and NL63 (Cov-HKU1, NL63, 229E, and OC43, respectively); human metapneumovirus (hMPV); respiratory syncytial virus (RSV); human rhinovirus/enterovirus (Rhino/Entero); as well as Chlamydophila pneumoniae, Mycoplasma pneumoniae, and Bordetella pertussis.
Our study indicated that the FilmArray RP assay significantly expands our ability to diagnose multiple respiratory infections caused by viruses and atypical bacteria. The array can detect 19 respiratory organisms simultaneously, with a high detection rate, in 65 min. Our study also revealed the age groups of patients with RTIs as well as the seasonal distributions of different organisms causing RTIs. This study also provided new insights into the current status of pertussis infection in Japan.
Nevertheless, the ultimate question about the true clinical impact of these assays remains unanswered. A few studies, primarily retrospective cohort studies, have evaluated and compared clinical outcomes such as the length of stay (LOS) and antibiotic use in patients diagnosed using conventional tests and in those diagnosed using rapid multiplex polymerase chain reactions (PCRs). In one study, the results of a multivariate analysis showed that adult patients diagnosed with influenza virus infection using a multiplex PCR, rather than conventional tests, performed in the ED were less likely to be admitted, had significantly lower LOS, and had shorter antimicrobial duration. A decrease in antibiotic use was also observed in an outpatient setting when patients were diagnosed using multiplex PCRs.
To better address the impact of multiplex panels, additional studies in specific patient populations (e.g., immunocompromised hosts) and on outcomes other than antibiotic use and LOS are needed. The results of these studies would help identify specific clinical scenarios or patient populations that would benefit the most from the use of molecular diagnosis.