Small quantities of respiratory syncytial virus RNA only in large droplets around infants hospitalized with acute respiratory infections.

BACKGROUND: Respiratory syncytial virus (RSV) is a major cause of respiratory tract infections in young children. The predominant transmission routes for RSV are still a matter of debate. Specifically, it remains unclear if RSV can be transmitted through the air and what the correlation is between the amount of RSV in nasopharynx samples and in the air. METHODS: The amount of RSV in the air around hospitalized RSV infected infants in single-patient rooms was quantified using a six-stage Andersen cascade impactor that collects and fractionates aerosols and droplets according to size. RSV shedding in the nasopharynx of patients was followed longitudinally by quantifying RSV RNA levels and infectious virus in nasopharyngeal aspirates. Nose and throat swabs of parents and swabs of the patient's bedrail and a datalogger were also collected. RESULTS: Patients remained RSV positive during the air sampling period and infectious virus was isolated up to 9 days post onset of symptoms. In three out of six patients, low levels of RSV RNA, but no infectious virus, were recovered from impactor collection plates that capture large droplets > 7 µm. For four of these patients, one or both parents were also positive for RSV. All surface swabs were RSV-negative. CONCLUSIONS: Despite the prolonged detection of infectious RSV in the nasopharynx of patients, only small amounts of RSV RNA were collected from the air around three out of six patients, which were primarily contained in large droplets which do not remain suspended in the air for long periods of time.

Pitfalls in interpretation of CT-values of RT-PCR in children with acute respiratory tract infections.

BACKGROUND: The relation between viral load and disease severity in childhood acute respiratory tract infections (ARI) is not fully understood. OBJECTIVES: To assess the clinical relevance of the relation between viral load, determined by cycle threshold (CT) value of real-time reverse transcription-polymerase chain reaction assays and disease severity in children with single- and multiple viral ARI. STUDY DESIGN: 582 children with ARI were prospectively followed and tested for 15 viruses. Correlations were calculated between CT values and clinical parameters. RESULTS: In single viral ARI, statistically significant correlations were found between viral loads of Respiratory Syncytial Virus (RSV) and hospitalization and between viral loads of Human Coronavirus (HCoV) and a disease severity score. In multiple-viral ARI, statistically significant correlations between viral load and clinical parameters were found. In RSV-Rhinovirus (RV) multiple infections, a low viral load of RV was correlated with a high length of hospital stay and a high duration of extra oxygen use. The mean CT value for RV, HCoV and Parainfluenza virus was significantly lower in single- versus multiple infections. CONCLUSION: Although correlations between CT values and clinical parameters in patients with single and multiple viral infection were found, the clinical importance of these findings is limited because individual differences in host-, viral and laboratory factors complicate the interpretation of statistically significant findings. In multiple infections, viral load cannot be used to differentiate between disease causing virus and innocent bystanders.

Single- and multiple viral respiratory infections in children: disease and management cannot be related to a specific pathogen.

BACKGROUND: The number of viral pathogens associated with pediatric acute respiratory tract infection (ARI) has grown since the introduction of reverse transcription real-time polymerase chain reaction (RT-PCR) assays. Multiple viruses are detected during a single ARI episode in approximately a quarter of all cases. The clinical relevance of these multiple detections is unclear, as is the role of the individual virus. We therefore investigated the correlation between clinical data and RT-PCR results in children with single- and multiple viral ARI. METHODS: Data from children with ARI were prospectively collected during two winter seasons. RT-PCR testing for 15 viruses was performed in 560 ARI episodes. In the patients with a single-viral etiology, clinical data, laboratory findings, patient management- and outcome data were compared between the different viruses. With this information, we compared data from children of whom RT-PCR data were negative, with children with single- and multiple viral positive results. RESULTS: The viral detection rate was 457/560 (81.6%) of which 331/560 (59.1%) were single infections and 126/560 (22.5%) were multiple infections. In single viral infections, some statistically significant differences in demographics, clinical findings, disease severity and outcome were found between children with different viral etiologies. However, no clinically recognizable pattern was established to be virus-specific. In a multivariate analysis, the only variables that were correlated with longer hospital stay were the use of oxygen and nebulizer therapy, irrespective of the viral pathogen. Children with RT-PCR positive test results had a significant higher disease severity, fever, length of hospital stay, days of extra oxygen supply, and days of antibiotic treatment than children with a negative RT-PCR test result. For children with single- versus children with multiple positive RT-PCR test results, these differences were not significant. CONCLUSIONS: Disease (severity), management and outcome in pediatric ARI are not associated with a specific virus. Single- and multiple viral ARI do not significantly differ with regard to clinical outcome and patient management. For general pediatrics, RT-PCR assays should be restricted to pathogens for which therapy is available or otherwise may have clinical consequences. Further research with an extended panel of RT-PCR assays and a larger number of inclusions is necessary to further validate our findings.

PCR testing for paediatric acute respiratory tract infections.

Acute respiratory tract infection (ARI) is a frequently occurring disease in children. It is a clinical diagnosis for which no internationally accepted diagnostic test is available. The majority of ARI is viral in origin, though diagnostic tests for viruses were rarely performed in the past. In the past 2 decades, new molecular techniques have been introduced in many hospitals. They are capable of generating a high yield of viral and bacterial diagnoses, but their impact upon clinical practices is still questionable. In this paper, we discuss the difficulties of diagnosing ARI in children, the indications for conventional and new diagnostics and their implications.

Bordetella pertussis: an underreported pathogen in pediatric respiratory infections, a prospective cohort study.

BACKGROUND: The incidence of pertussis has been increasing worldwide. In the Netherlands, the seroprevalence has risen higher than the reported cases, suggesting that laboratory tests for pertussis are considered infrequently and that even more pertussis cases are missed. The objective of our study was to determine the frequency of pertussis in clinically unsuspect cases compared to suspect cases with the intention of finding clinical predictors. METHODS: The present prospective cohort study was part of a controlled clinical trial evaluating the impact of molecular diagnostics on clinical decision making in pediatric respiratory infections, performed during 2 winter seasons. For this study, in the first season pertussis was only tested in case of clinical suspicion, in the second season, pertussis was also tested without clinical suspicion. Multivariate and univariate analysis were performed using SPSS 18 and Statistical software 'R'. RESULTS: In the two seasons respectively 22/209 (10,5%) and 49/373 (13,1%) cases were clinically suspected of pertussis. Bordetella pertussis was detected by real time RT-PCR in respectively 2/22 (9,1%) and 7/49 (14,3%) cases. In the second season an additional 7 cases of pertussis were found in clinically unsuspected cases (7/257 = 2,7%). These additional cases didn't differ in clinical presentation from children without a positive test for pertussis with respect to respiratory symptoms. CONCLUSIONS: Pertussis in children sometimes mimics viral respiratory tract infections. If pertussis diagnostics are based on clinical suspicion alone, about 1 in 5 cases (19%) is missed. Despite widely accepted clinical criteria, paroxysmal cough is not a good predictor of pertussis. To prevent spreading, physicians should include B. pertussis in routine diagnostics in respiratory tract infections.

Clinical impact of RT-PCR for pediatric acute respiratory infections: a controlled clinical trial.

OBJECTIVE: Real-time polymerase chain reaction (RT-PCR) testing is a quick sensitive method for detecting respiratory pathogens. We evaluated the diagnostic yield of RT-PCR assays and measured the effect of rapid reporting on patient care. METHODS: In a controlled clinical trial, nasal wash specimens were obtained from patients <12 years of age with suspected acute respiratory infections. In addition to the standard hospital protocol, RT-PCR assays for 17 pathogens were performed. The RT-PCR results were communicated to the clinicians within 12 to 36 hours in the intervention group and after 4 weeks in the control group. RESULTS: A total of 583 patients were included (mean age: 8.1 months [range: 0-107.5 months]): 298 in the intervention group and 285 in the control group. Eighty-two percent of nasal wash specimens tested positive for ≥1 pathogen. Respiratory syncytial virus was the most frequently encountered (55%) pathogen. There were no significant differences between the groups with respect to hospital admissions (intervention group: 223 admissions; control group: 211 admissions; P = .825), length of hospital stay (mean ± SD: 3.68 ± 2.68 days [intervention group] and 3.96 ± 2.67 days [control group]; P = .178), or duration of antibiotic use (mean ± SD: 6.52 ± 2.15 days [intervention group] and 6.97 ± 2.86 days [control group]; P = .490), when antibiotic treatment had been initiated. CONCLUSIONS: RT-PCR testing has a high yield of viral diagnoses, but rapid communication does not lead to decreases in hospital admissions, shorter hospital stays, or less antibiotic use for children with acute respiratory infections.