Positive Rapid Influenza Diagnostic Test Research Articles

Importance of History Taking and Physical Examination Before Rapid Laboratory Test for Seasonal Influenza Virus: A Single-Center Multiple Logistic Analysis.

Background Despite several rapid influenza diagnostic tests (RIDTs), they are predicting whether a patient has influenza before rapid testing is important. Here, we assessed factors predictive of a positive flu test via RIDTs by combining interviews and physical examination. Methods We analyzed the relationship between interviews and physical findings and results of RIDTs using multivariable logistic regression. Results Two hundred seventy-six children were enrolled throughout the 2018-2019 flu season. Accordingly, 115 patients (41.7%) were positive for flu A. Our logistic regression model identified age, body temperature, and the existence of upper respiratory symptoms as significant factors for predicting positive for RIDTs, with odds ratios (OR) of 1.17 [95% CI (confidence interval): 1.08-1.25]/+Δ1year old, 1.70 (95% CI: 1.27-2.27)/+Δ1 ℃, and 5.08 (95% CI: 2.57-10.00) for respiratory symptoms. In addition, the OR for sick contact was 7.67 (95% CI: 3.96-14.90). Our logistic regression model showed an area under the curve (AUC) of 0.84. History of vaccination was not identified as a significant factor in positive RIDTs. Conclusions The existence of sick contact was associated with a positive flu test via RIDTs. Although RIDTs are an easy and quick method for detecting the flu virus, we should perform the appropriate identification of cases for RIDTs by combining interviews and physical findings.

Practice patterns and perceptions of influenza testing amongst pediatric urgent care providers

IntroductionDespite a sensitivity of 50% to 70% the rapid influenza diagnostic test (RIDT) continues to play an important role in clinical decision-making due to its quick turn-around time, high specificity, relative simplicity of use, and low cost. MethodsA quantitative study using a web-based survey was distributed to 110 members of the Society of Pediatric Urgent Care aimed to assess RIDT use for diagnosis and management of influenza in outpatient pediatric patients. ResultsResponses from 61 providers were received. Forty-two percent (95% CI 29.5−54.5%) of respondents report higher confidence in their diagnosis of influenza with the aid of a positive RIDT. 28% of respondents (95% CI 16.6−39.4%) report a higher likelihood of prescribing antiviral medications to low-risk patients if an RIDT is positive than without laboratory confirmation. ConclusionMost pediatric urgent care respondents reported higher confidence in their diagnosis and higher likelihood of prescribing antivirals with a positive RIDT rather than by clinical symptoms alone.

Association of physician experience with a higher prescription rate of anti-influenza agents in low-risk patients.

During the influenza season, most patients suspected of having influenza undergo rapid influenza diagnostic tests (RIDTs) in Japan despite their low sensitivity. However, the physician's actual rationale for prescribing antivirals, besides the results of RIDTs, remains poorly understood. Our study sought to identify the role of clinical information and physicians' experience in the initiation of anti-influenza agents. We retrospectively reviewed 380 patients who underwent RIDTs at the emergency department of our hospital from September 2018 to May 2019. Data regarding sex, age, etc., which could affect the decision of prescribing antivirals, were extracted from medical records. We performed logistic regression analysis to analyze the concurrent effect of potentially relevant clinical factors, results of RIDTs, and the physician's status on antiviral prescription. Multivariable analysis revealed that a positive RIDT had the largest effect on antiviral prescription, followed by physician status, high regional influenza activity, and patients' presentation within 12h of symptom onset. Patient's age, comorbidities, and presentation after 48h of symptom onset were not associated with antiviral treatment. Physicians with more years of experience were significantly more likely to prescribe antivirals for patients with low risk of complications. Our findings revealed the physicians' rationale for initiating antiviral treatment and the discrepancy with guideline indications of antivirals, which is the patient's age and comorbidities. Physicians, especially those with more than 3years of experience, frequently prescribed antivirals for patients with low risk of complications; thus, educational interventions against this population could be useful to improve this situation.

Streptococcal sepsis and periorbital cellulitis as a complication of influenza in a 4-year-old girl

Influenza may pave the way for some specific bacterial infections. In this case study we present a rare complication of influenza A infection – periorbital cellulitis followed by streptococcal toxic shock syndrome and scarlet fever. A 4-year-old otherwise healthy girl presented with her mother to a general practitioner with fatigue, irritability and fever not responding to antipyretics. Due to the positive rapid influenza diagnostic test, treatment with oseltamivir was implemented. The Quick Strep Test was negative. During the following days, the patient’s condition worsened, leading to an admission to a paediatric otolaryngology unit. Doctors observed an asymmetrical swelling of the lids with exophthalmos of the right eye, pharyngitis, petechiae in skin folds, a strawberry tongue and skin exfoliation on the lips. The patient was treated with intravenous broadspectrum antibiotics (cefotaxime, vancomycin) and underwent drainage of sinuses, without any significant improvement. On the following day, the girl showed signs of systemic infection, confusion and further swelling of both eyes, and therefore was moved to an intensive care unit. Computed tomography of the head showed signs of periorbital cellulitis with destruction of the surrounding bones. After obtaining a positive blood culture for group A streptococcus, penicillin and clindamycin were immediately administered. The patient’s condition improved within 24 hours. The described case emphasises the importance of yearly influenza vaccination, especially in the groups with risk factors like very young age. Early diagnosis of the streptococcal infection as a complication of influenza and a targeted treatment may prevent the potentially fatal outcome in the form of streptococcal toxic shock syndrome.

The impact of early neuraminidase inhibitor therapy on clinical outcomes in patients hospitalised with influenza A-related pneumonia: a multicenter, retrospective study

BackgroundGuidelines emphasize prompt antiviral treatment in severe influenza patients. Although nearly a 50% of severe influenza present with pneumonia, the effect of early (≤ 2 days after illness onset) neuraminidase inhibitor (NAI) use on the clinical outcomes of influenza A-related pneumonia (FluA-p) has rarely been assessed. Furthermore, data about the administration of NAIs in the real-world management of Flu-p in China are limited.MethodsData of patients hospitalised with FluA-p from five teaching hospitals in China from 1 January 2013 to 31 December 2018 were reviewed retrospectively. The impact of early NAI therapy on the outcomes in FluA-p patients, and the indications of early NAI administration by clinicians were evaluated by logistic regression analysis.ResultsIn total, 693 FluA-p patients were included. Of these patients, 33.5% (232/693) were treated early. After adjusting for weighted propensity scores for treatment, systemic corticosteroid and antibiotic use, a multivariate logistic regression model showed that early NAI therapy was associated with decreased risk for invasive ventilation [odds ratio (OR) 0.511, 95% confidence interval (CI) 0.312–0.835, p = 0.007) and 30-day mortality (OR 0.533, 95% CI 0.210–0.807, p < 0.001) in FluA-p patients. A multivariate logistic regression model confirmed early NAI use (OR 0.415, 95% CI 0.195–0.858, p = 0.001) was a predictor for 30-day mortality in FluA-p patients and a positive rapid influenza diagnostic test was the only indication (OR 3.586, 95% CI 1.259–10.219, p < 0.001) related to the prescription of early NAI by clinicians.ConclusionsEarly NAI therapy is associated with better outcomes in FluA-p patients. Improved education and training of clinicians on the guidelines of influenza are needed.

Influenza laboratory testing and its application in timely Department of Defense biosurveillance

ObjectiveTo describe influenza laboratory testing and results in the Military Health System and how influenza laboratory results may be used in DoD Electronic Surveillance System for Early Notification of Community-based Epidemics (ESSENCE)IntroductionTimely influenza data can help public health decision-makers identify influenza outbreaks and respond with preventative measures. DoD ESSENCE has the unique advantage of ingesting multiple data sources from the Military Health System (MHS), including outpatient, inpatient, and emergency department (ED) medical encounter diagnosis codes and laboratory-confirmed influenza data, to aid in influenza outbreak monitoring. The Influenza-like Illness (ILI) syndrome definition includes ICD-9 or ICD-10 codes that may increase the number of false positive alerts. Laboratory-confirmed influenza data provides an increased positive predictive value (PPV). The gold standard for influenza testing is molecular assays or viral culture. However, the tests may take 3-10 days to result. Rapid influenza diagnostic tests (RIDTs) have a lower sensitivity, but the timeliness of receiving a result improves to within &lt;15 minutes. We evaluate the utility of RIDTs for routine ILI surveillance.MethodsAdministrative medical encounters for ILI and influenza laboratory-confirmed data were analyzed from the MHS from June 2013 – September 2017 (Figure 1). The medical encounters and laboratory data include outpatient, inpatient, and ED data. The ILI syndrome case definition is a medical encounter during the study period with an ICD-9 or ICD-10 codes in any diagnostic position (ICD-9 codes = 79.99, 382.9, 460, 461.9, 465.8, 465.9, 466.0, 486, 487.0, 487.1, 487.8, 488, 490, 780.6, or 786.2; ICD-10 codes = B97.89, H66.9, J00, J01.9, J06.9, J09, J09.X, J10, J10.0, J10.1, J10.2, J10.8, J11, J11.0, J11.1, J11.2, J11.8, J12.89, J12.9, J18, J20.9, J40, R05, R50.9). The ILI dataset was limited to care provided in the MHS as laboratory data is only available for direct care. We describe influenza laboratory testing practices in the MHS. We aggregated the ILI encounters and RIDT positive results into daily counts and generated a weekly Pearson’s correlation.ResultsInfluenza tests are ordered throughout the year; the mean weekly percentage of ILI encounters in which an influenza laboratory test is ordered is 5.62%, with a range from 0.68% in the off season to 19.2% during peak influenza activity. The mean weekly percentage of positive influenza laboratory results among all ILI encounters is 0.82%, with a range from 0.01% to 5.73% (Figure 2). The percent of ILI encounters in which a test is ordered increases as the influenza season progresses. Influenza laboratory tests conducted in the MHS include RIDTs, PCR, culture, and DFA. Among all influenza tests ordered in the MHS, 66.0% were RIDTs, 22.7% were PCR, and 11.3% were viral culture. Often, a confirmatory test is ordered following a RIDT; 20% of RIDTs have follow-up tests. The mean timeliness of influenza test result data in the MHS was 11.26 days for viral culture, 2.94 days for PCR, and 0.11 days for RIDTs. The RIDT results were moderately correlated with ILI encounters for the entire year (mean weekly Pearson correlation coefficient rho=0.60, 95% CI: 0.55, 0.66, Figure 3). During the influenza season, the mean weekly Pearson correlation coefficient increases to rho=0.75, 95% CI: 0.70, 0.79.ConclusionsThe DoD has the unique advantage of access to the electronic health record and laboratory tests and results of all MHS beneficiaries. This analysis provides evidence for increased utilization of positive RIDTs in ESSENCE. The moderate correlation between the ILI syndrome and positive RIDTs may be associated with ICD-10 codes included in the ILI syndrome definition that contribute to false positive influenza cases. Ongoing research is focused on improving this ILI syndrome definition using ICD-10 codes. Rapid influenza diagnostic tests provide more timely results than other influenza test types. In conjunction with ILI medical encounter data, positive RIDT data provides a more complete and timely picture of the true burden of influenza on the MHS population for early warning of influenza outbreaks.

Influenza Antiviral Prescribing Practices and the Influence of Rapid Testing Among Primary Care Providers in the US, 2009-2016.

Early influenza antiviral treatment within 2 days of illness onset can reduce illness severity and duration. Reliance on low sensitivity rapid influenza diagnostic tests (RIDTs) to guide antiviral prescribing has been reported. We describe antiviral prescribing practices among primary care providers from a large surveillance network in the United States. From 2009-2016, a network of 36 to 68 outpatient clinics per year collected respiratory specimens and clinical data for patients with influenza-like illness (ILI). Specimens were tested for influenza using polymerase chain reaction (PCR). We used multivariable logistic regression to assess factors influencing antiviral prescribing. Among 13 540 patients with ILI, 2766 (20%) were prescribed antivirals. In age groups recommended to receive empiric antiviral treatment for suspected influenza, 11% of children <2 years and 23% of adults ≥65 years received a prescription. Among 3681 patients with a positive PCR test for influenza, 40% tested negative by RIDT. In multivariable analysis, prescription receipt was strongly associated with a positive RIDT (adjusted odds ratio [aOR] 12, 95% CI 11-14) and symptom onset ≤2 days before visit (aOR 4.3, 95% CI 3.8-4.9). Antiviral prescribing was also more frequent among pediatric and private family practice clinics compared with community health centers (aOR 1.9, 95% CI 1.6-2.2, and 1.3, 95% CI 1.1-1.5, respectively). Primary care providers were more likely to prescribe antivirals to patients with a positive RIDT, but antivirals were prescribed infrequently even to patients in high-risk age groups. Understanding patient and provider characteristics associated with antiviral prescribing is important for communicating treatment recommendations.

Effect of rapid influenza diagnostic tests on patient management in an emergency department.

ObjectiveWe evaluated the effect of rapid influenza diagnostic tests (RIDTs) on patient management in an emergency department for 3 years after 2009, and also identified factors associated with the choice of treatment for patients with influenza-like illnesses.MethodsThe study period consisted of three influenza epidemic seasons. Patients older than 15 years who underwent RIDTs in the emergency department and were then discharged without admission were included.ResultsA total of 453 patients were enrolled, 114 of whom had positive RIDT results and 339 had negative results. Antiviral medication was prescribed to 103 patients (90.4%) who had positive RIDT results, while 1 patient (0.3%) who tested negative was treated with antivirals (P<0.001). Conservative care was administered to 11 RIDT-positive patients (9.6%) and 244 RIDT-negative patients (72.0%) (P<0.001). Symptom onset in less than 48 hours, being older than 65 years, and the presence of comorbidities were not associated with the administration of antiviral therapy.ConclusionRIDT results had a critical effect on physician decision-making regarding antiviral treatment for patients with influenza-like illnesses in the emergency department. However, symptom onset in less than 48 hours, old age, and comorbidities, which are all indications for antiviral therapy, were not found to influence the administration of antiviral treatment.

Influenza: Underestimated in Children Below 2 Years of Age.

Children under 2years of age may receive antiviral therapy when influenza is suspected. Signs of influenza are frequently unclear and testing is indicated. The aim of the study was to assess the usefulness of clinical signs and the rapid influenza diagnostic test (RIDT) in diagnosing influenza and in choosing the appropriate treatment. In the 2015-2016 influenza season, 89 children under 2years of age (56.7% of 157 children diagnosed with influenza) were hospitalized. There were 74 RIDT and 70 reverse transcription polymerase chain reactions (RT-PCR) performed for the purpose of diagnosis, either test per child. Eighty-three percent of children (74/89) presented with fever, 55.1% (49/89) with cough, and 39.3% (35/89) with both cough and fever. The RIDT was positive in 31.1% (23/74) of cases. The highest percentage of positive RIDT was within the first 24h of disease, decreasing dramatically thereafter (70% vs. 13-17%, respectively). The RIDT shortened the time to diagnosis by 43.8h/patient (an average €149 gain in treatment costs). The mean delay for RT-PCR-based diagnosis was 33.5h/patient (an average €114 loss in treatment costs). We conclude that clinical signs have a low diagnostic sensitivity in children under 2years of age. Likewise, RIDT is of low sensitivity, being diagnostically useful only in the first 24h. The PCR is recommended for the diagnosis, but that requires a constant access to the method.

Effectiveness of a pharmacist-physician collaborative program to manage influenza-like illness

ObjectivesTo examine the effectiveness of collaborative physician–community pharmacist programs to treat influenza-like illness (ILI) with respect to clinical outcomes and health care utilization. DesignProspective multicenter cohort study. SettingFifty-five pharmacies in Michigan, Minnesota, and Nebraska. PatientsAdult patients presenting to the pharmacy with ILI during the 2013–14 influenza season (October 1, 2013 to May 30, 2014). InterventionPharmacists screened adult patients presenting with ILI, completed a brief physical assessment, performed a point-of-care rapid influenza diagnostic test (RIDT), and provided appropriate referral or treatment per an established collaborative practice agreement (CPA) with a licensed prescriber. Pharmacists followed-up with patients 24 to 48 hours after the encounter to assess patient status and possible need for further intervention. Main outcome measuresNumber of patients screened, tested, and treated for influenza. ResultsOf the 121 patients screened, 45 (37%) were excluded and referred to their primary care provider or an urgent care facility for management. Of the 75 patients (62%) eligible for participation, 8 (11%) had a positive RIDT and were managed according to the CPA. Of the patients tested, 34.6% had no primary care physician and 38.7% visited the pharmacy outside of normal office hours. Only 3% of patients reported feeling worse at follow-up. ConclusionThis study describes a physician-pharmacist collaborative model for treating ILI. Using an evidence-based CPA, pharmacists were able to provide timely treatment to patients with and without influenza.

Impact of rapid influenza diagnostic test on physician estimation of viral infection probability in paediatric emergency department during epidemic period

BackgroundThe clinical diagnosis of influenza is difficult in the younger children. ObjectivesEvaluate the impact of rapid influenza diagnostic test (RIDT) on clinicians’ estimation of the clinical probability of influenza in children. Study designThis prospective study included children aged from 1 month to 5 years who were admitted in a university paediatric emergency department during an influenza epidemic period and presented with fever without source. The RIDT Quickvue® was performed on nasopharyngeal aspiration and results were confirmed with immunofluorescence and/or PCR. The clinical probability of influenza and serious bacterial infection (SBI) was evaluated for each child before and after the physician(s) was informed of the RIDT results. Results170 children were included from January 15th through March 18th, 2013. After the only clinical examination, the overall clinical probability of influenza was 66.0% [CI 95%: 63.04–68.4], and was significantly increased at 92.4% [CI 95%: 89.5–95.3] in case of positive RIDT and significantly decreased at 30.8% [CI 95%: 29.0–32.5] in case of negative RIDT without knowing the results of laboratory tests. Whereas the initial clinical probability of influenza were appropriate regarding the prevalence (66.0% vs. 57.0%), the probability of SBI was overestimated (30.2% vs. 8.8%). The RIDT result positive enabled a significant decrease in orders for chest X-rays (64,4% vs. 45.8%, p<0,05) and laboratory tests (71,1% vs. 41.1%, p<0,05). ConclusionsThe RIDT seems to be a useful diagnostic tool for ED clinicians in epidemic conditions. Improving clinician estimation of flu probability would reduce orders for imaging and testing.

Pregnancy and severe influenza infection in the 2013-2014 influenza season.

To describe the epidemiologic and clinical characteristics of critically ill pregnant and postpartum women with influenza infection reported in the 2013-2014 season. The California Department of Public Health conducts surveillance for patients with laboratory-confirmed influenza who die or require hospitalization in intensive care units. For this case series, we reviewed data on pregnant and postpartum (6 weeks or less from delivery) women reported in the 2013-2014 influenza season. From September 29, 2013, through May 17, 2014, 17 pregnant women with severe influenza were reported. The median age was 29 years (range 17-44 years). Sixteen (94%) were in the second or third trimester. Fifteen (88%) patients were hospitalized, nine (53%) required mechanical ventilation, five (29%) required emergent cesarean delivery, and four (24%) died. Of 14 patients with available information, only two (14%) received influenza vaccination during pregnancy. Seven patients who tested positive by polymerase chain reaction also had rapid influenza diagnostic testing performed; only one (14%) had a positive rapid influenza diagnostic test results. Fifteen patients received antiviral treatment; four (27%) began treatment within 48 hours of symptom onset. One additional patient was 36 days postpartum and required intensive care unit admission and mechanical ventilation for influenza-associated acute respiratory distress syndrome. Influenza remains a significant cause of morbidity and mortality in pregnant and postpartum women; in our series, a majority were not vaccinated. During the influenza season, pregnant women with suspected influenza should receive prompt empiric antiviral therapy, regardless of rapid influenza diagnostic test results or vaccination status. III.

Modes of transmission of influenza B virus in households.

IntroductionWhile influenza A and B viruses can be transmitted via respiratory droplets, the importance of small droplet nuclei “aerosols” in transmission is controversial.Methods and FindingsIn Hong Kong and Bangkok, in 2008–11, subjects were recruited from outpatient clinics if they had recent onset of acute respiratory illness and none of their household contacts were ill. Following a positive rapid influenza diagnostic test result, subjects were randomly allocated to one of three household-based interventions: hand hygiene, hand hygiene plus face masks, and a control group. Index cases plus their household contacts were followed for 7–10 days to identify secondary infections by reverse transcription polymerase chain reaction (RT-PCR) testing of respiratory specimens. Index cases with RT-PCR-confirmed influenza B were included in the present analyses. We used a mathematical model to make inferences on the modes of transmission, facilitated by apparent differences in clinical presentation of secondary infections resulting from aerosol transmission. We estimated that approximately 37% and 26% of influenza B virus transmission was via the aerosol mode in households in Hong Kong and Bangkok, respectively. In the fitted model, influenza B virus infections were associated with a 56%–72% risk of fever plus cough if infected via aerosol route, and a 23%–31% risk of fever plus cough if infected via the other two modes of transmission.ConclusionsAerosol transmission may be an important mode of spread of influenza B virus. The point estimates of aerosol transmission were slightly lower for influenza B virus compared to previously published estimates for influenza A virus in both Hong Kong and Bangkok. Caution should be taken in interpreting these findings because of the multiple assumptions inherent in the model, including that there is limited biological evidence to date supporting a difference in the clinical features of influenza B virus infection by different modes.

Clinical diagnosis of pandemic A(H1N1) 2009 influenza in children with negative rapid influenza diagnostic test by lymphopenia and lower C‐reactive protein levels

BackgroundThe sensitivity of rapid influenza diagnostic test (RIDT) of children with influenza-like illness (ILI) remains low.ObjectiveWe compare the parameters between pandemic A(H1N1) 2009 influenza with negative RIDT and ILI not H1N1 for improving the low sensitivity of RIDT for children with ILI.MethodsIn a cohort of consecutive laboratory-confirmed H1N1 influenza, we identified 150 H1N1 children with positive RIDT, 152 H1N1 children with negative RIDT, and 75 children with ILI not H1N1. Viral load in throat, complete blood count (CBC), and C-reactive protein (CRP) levels between H1N1 children with negative RIDT and children with ILI not H1N1 were assessed.ResultsThe diagnostic sensitivity of the RIDT was 45·5%. An analysis of CBC and CRP levels indicated that H1N1 children with negative RIDT had lower total leukocyte, neutrophil, lymphocyte, and basophil counts, and serum CRP levels (P < 0·01). Lymphocyte counts less than 1500 cells/mm3 and CRP levels <15 mg/l, determined by a receiver operating characteristic curve, showed a diagnostic sensitivity of 52·5% and 80·7%, respectively. Combining the lymphocyte counts and CRP levels provided a diagnostic sensitivity of 91·5%. Moreover, H1N1 children with negative RIDT had a lower viral load than those with positive RIDT (3·33 versus 4·48 log10 copies/ml, P < 0·001); the viral load was negatively correlated to the lymphocyte count (P < 0·001).ConclusionsA combination of a low lymphocyte count and a low CRP level could, in the early disease phase, provide a useful screening for H1N1 children with false-negative RIDT, potentially facilitating differential diagnoses.

Estimating the Influenza Vaccine Effectiveness against Medically Attended Influenza in Clinical Settings: A Hospital-Based Case-Control Study with a Rapid Diagnostic Test in Japan

BackgroundInfluenza vaccine effectiveness (VE) studies are usually conducted by specialized agencies and require time and resources. The objective of this study was to estimate the influenza VE against medically attended influenza using a test-negative case-control design with rapid influenza diagnostic tests (RIDT) in a clinical setting.MethodsA prospective study was conducted at a community hospital in Nagasaki, western Japan during the 2010/11 influenza season. All outpatients aged 15 years and older with influenza-like illnesses (ILI) who had undergone RIDT were enrolled. A test-negative case-control design was applied to estimate the VEs: the cases were ILI patients with positive RIDT results and the controls were ILI patients with negative RIDT results. Information on patient characteristics, including vaccination histories, was collected using questionnaires and medical records.ResultsBetween December 2010 and April 2011, 526 ILI patients were tested with RIDT, and 476 were eligible for the analysis. The overall VE estimate against medically attended influenza was 47.6%, after adjusting for the patients' age groups, presence of chronic conditions, month of visit, and smoking and alcohol use. The seasonal influenza vaccine reduced the risk of medically attended influenza by 60.9% for patients less than 50 years of age, but a significant reduction was not observed for patients 50 years of age and older. A sensitivity analysis provided similar figures.ConclusionThe test-negative case-control study using RIDT provided moderate influenza VE consistent with other reports. Utilizing the commonly used RIDT to estimate VE provides rapid assessment of VE; however, it may require validation with more specific endpoint.

Field performance of clinical case definitions for influenza screening during the 2009 pandemic

PurposeThe aim of this study was to assess the performance of 3 different influenza-like illness (ILI) case definitions, adopted by the European (European-CDC), USA (USA-CDC), and Taiwan Centers for Disease Prevention and Control (Taiwan-CDC), as screening tools for influenza during the 2009 H1N1 pandemic. MethodsFrom August 15 to 30, 2009, all emergency department patients with clinical symptoms or at epidemiologic risk for influenza were enrolled in an observational cohort study. Influenza diagnosis was established by positive rapid influenza diagnostic test or virus isolation. Sensitivity, specificity, positive predictive value, and negative predictive value of the European-, USA, and Taiwan-CDC ILI case definitions for screening were determined. ResultsA total of 870 patients were screened during the study period. Rapid influenza diagnostic test was positive in 315 patients, 273 (85.6%) of whom had fever duration less than 72 hours. Virus isolation identified 4 more patients with influenza A initially negative by rapid influenza diagnostic test. The mean (SD) age of these 319 patients was 24.3 (18.1) years. Of the 870 screened patients, 670 (77.0%), 476 (54.7%), and 325 (37.4%) met the European-, USA-, and Taiwan-CDC ILI case definition, respectively. Screening sensitivity was 95%, 77.7%, and 57.7% and specificity was 33.4%, 58.6%, and 74.4%, respectively. Differences in sensitivity and specificity between any 2 of the 3 groups were statistically significant (P < .05). ConclusionFirst-line physicians should recognize the advantage and limitation of different ILI case definitions in influenza screening, especially confronted by pandemic or highly pathogenic avian influenza in the future.

Clinical evaluation of rapid point-of-care testing for detection of novel influenza A (H1N1) virus in a population-based study in Spain

Limited information exists on the performance of antigen-based rapid influenza diagnostic tests (RIDT) in diagnosing the novel influenza A pandemic (H1N1) 2009 virus. Large studies evaluating these tests in consecutive patients with a broad clinical spectrum of influenza-like illnesses are needed. We assessed the ClearView® Exact Influenza A & B test (Inverness Medical, Cologne, Germany) in comparison with real-time (r)RT-PCR for detection of the novel influenza A (H1N1) in a population-based prospective study of 1016 adults and children with suspected influenza in Spain. Three hundred and one (29.6%) patients had a positive sample with the rRT-PCR assay for influenza A and B viruses, with 297 (29.2%) confirmed cases of the novel influenza A pandemic (H1N1) 2009 virus. Fifty (16.8%) patients with confirmed A (H1N1) 2009 virus were admitted to hospital, with six of them to the intensive care unit. In comparison with rRT-PCR, the ClearView® Exact Influenza A & B test had a sensitivity of 19% (95% CI 14–23), a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 75% (95% CI 72–78). The sensitivity of the test remained low across all demographic and clinical strata. Although a positive RIDT performed well in predicting PCR-confirmed infection with pandemic H1N1 virus, the sensitivity was very low and a negative test result was a poor predictor of the absence of infection.

Performance of a Rapid Influenza Test in Children During the H1N1 2009 Influenza A Outbreak

To evaluate the performance of a rapid influenza diagnostic test (RIDT) in detecting H1N1 2009 influenza A virus in respiratory samples from pediatric patients in comparison to that of real-time reverse-transcriptase polymerase chain reaction (rRT-PCR) and viral culture. Methodology. This was a cross-sectional diagnostic-accuracy study conducted at a tertiary care children's hospital. Patients for whom the RIDT (BinaxNOW [Binax, Inc, Portland, ME]), viral culture, and rRT-PCR results were known were included. Sensitivity, specificity, and likelihood ratios (LRs) were calculated. A total of 3030 specimens had RIDT results paired with both rRT-PCR and viral culture results. With rRT-PCR as the reference, overall test sensitivity was 45% (95% confidence interval [CI]: 43.3%-46.3%) and specificity was 98.6% (95% CI: 98.1%-99%). Positive and negative LRs were 32.9 (95% CI: 22.9-45.4) and 0.56 (95% CI: 0.54-0.58), respectively. RIDT sensitivity was significantly higher in young infants and children younger than 2 years than in older children. Using viral culture as the reference standard, RIDT sensitivity was 55.5% (95% CI: 51.9%-95.6%) and specificity was 95.6% (95% CI: 95%-96.1%). The positive and negative LRs were 12.6 and 0.47, respectively. The RIDT had relatively poor sensitivity but excellent specificity in this consecutive series of respiratory specimens obtained from pediatric patients. Although a positive RIDT result was highly accurate in predicting infection with influenza type A H1N1 2009 in children, a negative RIDT result did not preclude a child having H1N1. Therefore, for children at high risk with influenza-like illnesses during high-prevalence periods of influenza, empiric initiation of antiviral therapy should be considered for patients with a negative RIDT result.

Clinical evaluation of rapid point-of-care testing for detection of novel influenza A (H1N1) virus in a population-based study in Spain

Limited information exists on the performance of antigen-based rapid influenza diagnostic tests (RIDT) in diagnosing the novel influenza A pandemic (H1N1) 2009 virus. Large studies evaluating these tests in consecutive patients with a broad clinical spectrum of influenza-like illnesses are needed. We assessed the ClearView® Exact Influenza A & B test (Inverness Medical, Cologne, Germany) in comparison with real-time (r)RT-PCR for detection of the novel influenza A (H1N1) in a population-based prospective study of 1016 adults and children with suspected influenza in Spain. Three hundred and one (29.6%) patients had a positive sample with the rRT-PCR assay for influenza A and B viruses, with 297 (29.2%) confirmed cases of the novel influenza A pandemic (H1N1) 2009 virus. Fifty (16.8%) patients with confirmed A (H1N1) 2009 virus were admitted to hospital, with six of them to the intensive care unit. In comparison with rRT-PCR, the ClearView® Exact Influenza A & B test had a sensitivity of 19% (95% CI 14–23), a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 75% (95% CI 72–78). The sensitivity of the test remained low across all demographic and clinical strata. Although a positive RIDT performed well in predicting PCR-confirmed infection with pandemic H1N1 virus, the sensitivity was very low and a negative test result was a poor predictor of the absence of infection.