Feasibility of diagnosing influenza within 24 hours of symptom onset in children 1–3 years of age

Abstract

Diagnosing influenza at an early stage of illness is important for the initiation of effective antiviral treatment. However, especially in young children, influenza often commences with an abrupt onset of fever, with full-blown respiratory symptoms developing only later. We determined the feasibility of diagnosing influenza in young children already during the first signs of the illness. During confirmed influenza activity, we obtained nasal swabs from children aged 1-3 years who presented as outpatients within 24 hours of the onset of fever (≥38.0°C). The specimens were tested for influenza viruses with viral culture, antigen detection, PCR, and a rapid point-of-care test (Actim Influenza A&B, Medix Biochemica, Finland). In addition, follow-up specimens were obtained from a proportion of children 3-7 days later. Influenza virus was detected already within 24 hours of symptom onset in 56 of 61 (92%; 95% CI 82-97%) children in whom influenza was eventually confirmed in the laboratory. A total of 158 rapid tests performed within 24 hours of symptom onset yielded a sensitivity of 90% (95% CI 74-98%) for influenza A viruses but only 25% (95% CI 3-61%) for influenza B viruses (P < 0.001), resulting in an overall sensitivity of 77% (95% CI 61-89%) and specificity of 99% (95% CI 95-100%) for all influenza viruses. In most young children, influenza can already be accurately diagnosed within 24 hours of symptom onset. The rapid point-of-care test used was sensitive and specific for diagnosing influenza A, but its sensitivity for influenza B was limited.

Signs and symptoms predicting influenza in children: a matched case–control analysis of prospectively collected clinical data

“…Several rapid test kits that can provide results within 15 min are available. The performance of these tests varies [26,27], but is usually good in children and during the early course of the illness when, also, the benefits of the antiviral treatment of influenza are greatest [10,25,28,29]. Pre-test probability of influenza Fig.…”

“…It should be noted, however, that our viral culture method included also subsequent immunoperoxidase staining with monoclonal antibodies [22]. In previous studies, this method has yielded a sensitivity of approximately 90% when compared with polymerase chain reaction (PCR)-based assays for the detection of influenza [10,25]. Furthermore, because the controls were selected in a blinded manner from a very large database of influenza virus-negative children, the probability for any individual child who may have been false-negative for influenza to end up in the control group was low.…”

The Effect of the Rapid Antigen Test for Influenza on Clinical Practice in the Emergency Department: A Comparison of Periods before and After the 2009 H1N1 Influenza Pandemic

“…(7)(8)(9) In one study, the Actim Influenza A&B kit (Medix Biochemica, Joensuu, Finland) has been shown to be 90.0% sensitive for the detection of influenza A virus. (10) Some small studies have shown that a positive RAT spurs changes in clinical practice. (11)(12)(13) In this study, we investigated the effect of RAT for influenza on the proportion of antibiotic administration, additional diagnostic tests, and the length of stay (LOS) in the ED.…”

Diagnostic Methods of Influenza a From Clinical Specimens: A Critical Review of Literature

“…Generally, the sensitivity of DFA is higher than that of the rapid antigen test. Studies have shown that DFA sensitivity is higher among pediatric patients, especially displaying signs of high fever and spreading high amounts of viruses and decreasing with patients above 30 years of age (Heinonen et al 2011).…”