Flocked nasal swab versus nasopharyngeal aspirate for detection of respiratory tract viruses in immunocompromised adults: a matched comparative study

<p>Abstract</p> <p>Background</p> <p>Several studies have compared nasal swabs to the more invasive nasopharyngeal aspirate (NPA) for detection of respiratory viruses. Mostly, the comparisons have been performed on immunocompetent children with upper respiratory tract symptoms. The results range from a relatively poor sensitivity for the swabs to an even higher sensitivity than for the NPA. We aimed to investigate the sensitivity of a flocked nasal swab (fNS) on immunocompromised adults with febrile neutropenia.</p> <p>Methods</p> <p>During 16 months, adults with a hematological disorder presenting with febrile neutropenia were enrolled in the study. Paired samples of the fNS and NPA were collected in the outer part of the nasal cavity and the nasopharynx, respectively. The samples were analyzed regarding a panel of 15 respiratory viruses by means of quantitative polymerase chain reaction. Furthermore, as an indirect measure of cell yield by either method, the copy number of the human beta actin gene was also determined. Cohen's kappa was calculated as a measure of agreement of the results obtained from either method. Wilcoxon signed-rank test was used for comparison of cell yield.</p> <p>Results</p> <p>A total of 98 paired samples from a total of 89 patients were collected. Twenty of the pairs had virus detected in at least one of the specimens; 11 in both, 7 in NPA only, and 2 in fNS only. For the fNS, the overall sensitivity for any virus and for rhinovirus only was 65% and 78%, respectively. NPA was significantly superior to the fNS in collecting epithelial cells.</p> <p>Conclusion</p> <p>We found the overall sensitivity of 65% to be too low to replace NPA with this sampling technique in this patient category.</p

Viral respiratory infections : Diagnosis and epidemiology

Background. Respiratory viral infections are common causes of human morbidity and mortality in children as well as in adults. Adenovirus, influenza virus, parainfluenza virus and respiratory syncytial virus (RSV) have been recognized for many years. During recent years two main events have influenced both the diagnosis and our knowledge of respiratory virus epidemiology: (1) Five new viruses have been described; (2) the use of molecular methods for the diagnosis of respiratory tract infections has been introduced. Objectives. The first objective of this thesis was to study the diversity of respiratory virus infections in Stockholm in different patient groups and using different diagnostic methods. The second objective was to study the molecular epidemiology of RSV. The third objective was to evaluate and compare the conventional diagnostic methods for respiratory viruses with new molecular diagnostic methods. Materials and Methods. In paper I the diagnostic results from 7303 respiratory specimens were analyzed retrospectively. The results were obtained by virus isolation and antigen detection with immunofluorescence. In paper II RSV strains from 234 frozen respiratory specimens were sequenced and genotyped. In paper III a real-time diagnostic platform for 15 respiratory viruses was developed and evaluated based on 585 frozen nasopharyngeal aspirates and after that evaluated based on diagnostic samples. In paper IV 37 infection episodes with multiple viral findings were compared with 94 infection episodes with single findings. Results. In paper I one or two viruses were found in 43% of the samples, with the highest proportion of positive samples among the oldest patients. RSV was the most common finding among children under five years of age, and influenza was the most common in adults and children over five years old. RSV was only found in 2% of patients over 81 years old. The genotyping of 234 strains in paper II showed that both RSV subgroups A and B were circulating during the 2002 2003 season. The two subgroups were further subdivided into two genotypes each. A comparison with available strains from other parts of the world showed a high degree of similarity. In paper III the diagnostic yield increased from 37% with conventional methods to 57% with the new diagnostic real-time PCR platform. The children with multiple findings were significantly older than those with single findings in the comparison between the two groups in paper IV. There was no difference between the groups regarding hospitalization time, diagnosis, CRP levels, signs on x-ray or oxygen treatment. Conclusions. By using a real-time PCR platform for viral respiratory tract infections, the diagnostic yield increased compared to virus isolation and antigen detection. Besides older age, no apparent differences between children with multiple findings and single findings were observed, indicating that prolonged sheddings from sequential infections rather than true multiple infections were detected. The low findings of RSV among the elderly indicate either that RSV is not common among the elderly in Sweden or that RSV infection appears before admission to hospital or that more sensitive methods than IF have to be used in the elderly. The high degree of similarity between strains from Sweden and other parts of the world supports the current theories on RSV epidemiology suggesting that local factors, such as local immunity in the population, are more important for the outcome of epidemics than globally circulating strains

Frequent Respiratory Viral Infections in Children with Febrile Neutropenia - A Prospective Follow-Up Study.

OBJECTIVE:Febrile neutropenia is common in children undergoing chemotherapy for the treatment of malignancies. In the majority of cases, the cause of the fever is unknown. Although respiratory viruses are commonly associated with this condition, the etiologic significance of this finding remains unclear and is therefore the subject of this study. STUDY DESIGN:Nasopharyngeal aspirates were collected during 87 episodes of febrile neutropenia in children age 0-18 years, being treated at a children's oncology unit between January 2013 and June 2014. Real-time polymerase chain reaction was used to determine the presence of 16 respiratory viruses. Follow-up samples were collected from children who tested positive for one or more respiratory viruses. Rhinoviruses were genotyped by VP4/VP2 sequencing. Fisher's exact test and Mann-Whitney U test were used for group comparisons. RESULTS:At least one respiratory virus was detected in samples from 39 of 87 episodes of febrile neutropenia (45%), with rhinoviruses the most frequently detected. Follow-up samples were collected after a median of 28 days (range, 9-74 days) in 32 of the 39 virus-positive episodes. The respiratory viral infection had resolved in 25 episodes (78%). The same virus was detected at follow-up in one coronavirus and six rhinovirus episodes. Genotyping revealed a different rhinovirus species in two of the six rhinovirus infections. CONCLUSION:The frequency of respiratory viral infections in this group of patients suggests an etiologic role in febrile neutropenia. However, these findings must be confirmed in larger patient cohorts

Respiratory Viruses in Hospitalized Children with Influenza-Like Illness during the H1n1 2009 Pandemic in Sweden

<div><h3>Background</h3><p>The swine-origin influenza A(H1N1)pdm09 pandemic of 2009 had a slower spread in Europe than expected. The human rhinovirus (HRV) has been suggested to have delayed the pandemic through viral interference. The importance of co-infections over time during the pandemic and in terms of severity of the disease needs to be assessed.</p> <h3>Objective</h3><p>The aim of this study was to investigate respiratory viruses and specifically the presence of co-infections with influenza A(H1N1)pdm09 (H1N1) in hospitalized children during the H1N1 pandemic. A secondary aim was to investigate if co-infections were associated with severity of disease.</p> <h3>Methods</h3><p>A retrospective study was performed on 502 children with influenza-like illness admitted to inpatient care at a pediatric hospital in Stockholm, Sweden during the 6 months spanning the H1N1 pandemic in 2009. Respiratory samples were analyzed for a panel of 16 viruses by real-time polymerase chain reaction.</p> <h3>Results</h3><p>One or more viruses were detected in 61.6% of the samples. Of these, 85.4% were single infections and 14.6% co-infections (2–4 viruses). The number of co-infections increased throughout the study period. H1N1 was found in 83 (16.5%) children and of these 12 (14.5%) were co-infections. HRV and H1N1 circulated to a large extent at the same time and 6.0% of the H1N1-positive children were also positive for HRV. There was no correlation between co-infections and severity of disease in children with H1N1.</p> <h3>Conclusions</h3><p>Viral co-infections were relatively common in H1N1 infected hospitalized children and need to be considered when estimating morbidity attributed to H1N1. Population-based longitudinal studies with repeated sampling are needed to improve the understanding of the importance of co-infections and viral interference.</p> </div

Co-infections over time.

<p>Number of children with co-infections over time in (a) all children and (b) H1N1-positive children. H1N1-positive co-infected children divided into co-infection with HRV (H1N1/HRV) and co-infection with other viruses (H1N1/other).</p

Genotyping of repeatedly rhinovirus positive samples collected during episodes of febrile neutropenia (black boxes) and at follow-up (white boxes).

<p>Genotyping of repeatedly rhinovirus positive samples collected during episodes of febrile neutropenia (black boxes) and at follow-up (white boxes).</p

Distribution of virus in H1N1-positive and H1N1-negative samples.

<p>Distribution of virus in H1N1-positive and H1N1-negative samples.</p

Viruses detected at time of follow up.

<p>Viruses detected at time of follow up.</p