Saliva as a Reliable and Non-Invasive Sample for Detecting Influenza A in Severe Acute Respiratory Infection Cases

Nasopharyngeal swab sampling can be limited by critical factors, such as dependence on medical staff, invasiveness, nosocomial transmission, and occupational exposure risk. This study aimed to investigate whether saliva and nasal vestibular swabs are suitable non-invasive alternatives to nasopharyngeal swabs for influenza A detection in severe acute respiratory infections (SARIs). Saliva samples demonstrated a higher sensitivity (87.5%) than did nasal vestibular swabs (31.3%) in RT-qPCR. While nasal vestibular swabs showed inconsistent results, saliva samples consistently tested positive, particularly within 7 days of symptom onset (100% positive agreement). In addition, diagnosis with RT-qPCR is often delayed because it requires trained laboratory technicians and facilities with appropriate laboratory settings. Therefore, the GenPad®, a rapid diagnostic device, was evaluated and showed promising performance (92.9%) compared with the efficiency of RT-qPCR. Factors such as the location of infection (upper vs. lower respiratory tract infections), sample collection timing, pre-collection instructions, and nucleic acid extraction possibly contributed to the detection efficiency. Despite the small sample size (n=16) and lack of influenza-negative controls, our findings support saliva as a viable self-collected diagnostic sample for influenza A diagnosis and surveillance programs. Non-invasive sampling mitigates discomfort, minimizes infection risk for healthcare workers, and improves testing capacity, particularly under frequent staff shortages during pandemics.