Neuraminidase Inhibitor Therapy Research Articles

Effects of Antiviral Therapy and Glucocorticoid Therapy on Fever Duration in Pediatric Patients with Influenza.

Background and Objectives: Considering developing resistance against neuraminidase inhibitors (NAIs) and their adverse reactions, restricted use of NAIs and use of alternative drugs should be considered for treating influenza. Although glucocorticoids (GCs) have been used for severe influenza, their effects on non-severe influenza have rarely been evaluated. This study aimed to evaluate the clinical responses to NAI therapy and GC therapy in pediatric patients with non-severe influenza. Materials and Methods: A total of 601 pediatric patients (<19 years of age) diagnosed with non-severe influenza were retrospectively recruited to evaluate the effects of NAI therapy and GC therapy. Post-admission fever duration and hospitalization duration were compared among four patient groups divided by the administered treatment: No therapy (n = 52), NAI therapy (n = 154), GC therapy (n = 123), and Both therapies (n = 272). Results: In a multivariate analysis with adjustment for confounding variables, the post-admission fever duration was not significantly different among the four patient groups. The post-admission fever duration tended to shorten with increasing age, longer pre-admission fever duration, and incidence of influenza A virus infection and lower respiratory tract infection. The type of administered treatment showed no significant effects on the post-admission fever duration in any subgroups according to patient age, pre-admission fever duration, influenza virus subtype, and clinical diagnosis. Conclusions: Symptomatic treatment rather than antiviral or GC therapy seems to be sufficient for patients with non-severe influenza, although the effects of NAI therapy and GC therapy according to their administered time and dose should be further evaluated.

The severity and risk factors for mortality in immunocompromised adult patients hospitalized with influenza-related pneumonia

ObjectiveTo explore disease severity and risk factors for 30-day mortality of adult immunocompromised (IC) patients hospitalized with influenza-related pneumonia (Flu-p).MethodA total of 122 IC and 1191 immunocompetent patients hospitalized with Flu-p from January 2012 to December 2018 were recruited retrospectively from five teaching hospitals in China.ResultsAfter controlling for confounders, multivariate logistic regression analysis showed that immunosuppression was associated with increased risks for invasive ventilation [odds ratio: (OR) 2.475, 95% confidence interval (CI): 1.511–4.053, p < 0.001], admittance to the intensive care unit (OR: 3.247, 95% CI 2.064–5.106, p < 0.001), and 30-day mortality (OR: 3.206, 95% CI 1.926–5.335, p < 0.001) in patients with Flu-p. Another multivariate logistic regression model revealed that baseline lymphocyte counts (OR: 0.993, 95% CI 0.990–0.996, p < 0.001), coinfection (OR: 5.450, 95% CI 1.638–18.167, p = 0.006), early neuraminidase inhibitor therapy (OR 0.401, 95% CI 0.127–0.878, p = 0.001), and systemic corticosteroid use at admission (OR: 6.414, 95% CI 1.348–30.512, p = 0.020) were independently related to 30-day mortality in IC patients with Flu-p. Based on analysis of the receiver operating characteristic curve (ROC), the optimal cutoff for lymphocyte counts was 0.6 × 109/L [area under the ROC (AUROC) = 0.824, 95% CI 0.744—0.887], sensitivity: 97.8%, specificity: 73.7%].ConclusionsIC conditions are associated with more severe outcomes in patients with Flu-p. The predictors for mortality that we identified may be valuable for the management of Flu-p among IC patients.

Neuraminidase inhibitors are effective and safe in reducing influenza complications: meta-analysis of randomized controlled trials.

BackgroundThere is scarce evidence verifying the impact of neuraminidase inhibitors (NAIs) in reducing influenza complications. The aim was to evaluate the available evidence from randomized-controlled trials (RCT) regarding the efficacy and safety of NAIs in reducing influenza complications. MethodsA systematic search of the literature was performed in the Cochrane Library, PubMed and Web of Science databases (2006–2019). Eligibility criteria were RCT that enrolled patients of any age or clinical severity with seasonal influenza (H1N1, H3N2, or B) or influenza-like syndrome and receiving NAIs comparing to placebo therapy. ResultsEighteen RCTs (9004 patients) were included: nine focused on oral oseltamivir, six on inhaled zanamivir, and three on intravenous peramivir. Administration of NAIs therapy significantly decreased the time to clinical resolution (median difference: -17.7 hours; and total influenza-related complications (OR: 0.64, 95%CI: 0.51–0.82). In addition, NAIs significantly decreased acute otitis media complication (OR: 0.50, 95%CI: 0.31–0.82) and need for antibiotic treatment (OR: 0.64, 95%CI: 0.46–0.90); and showed a trend towards a reduced occurrence of pneumonia (OR: 0.44, 95%CI: 0.10–2.00), bronchitis (OR: 0.80, 95%CI: 0.43–1.48), sinusitis (OR: 0.73, 95%CI: 0.40–1.32), asthma exacerbations (OR: 0.57, 95%CI: 0.28–1.16), and hospitalizations (OR: 0.57, 95%CI: 0.24–1.38). The overall proportion of AEs tend to increase with NAIs treatment (OR: 1.16, 95%CI: 0.92–1.47). Use of NAIs was associated with a significant increase of nausea and vomiting (OR: 1.61, 95%CI: 1.04–2.50) and a decrease on diarrhea (OR: 0.81, 95%CI: 0.65–1.00). ConclusionsNAIs are effective in reducing time to clinical resolution, total influenza-related complications, otitis media, and need of antibiotic administration. Reductions on mortality, pneumonia, asthma exacerbations or hospitalization rates only did demonstrate a trend benefit in favor of NAIs. The only significant AE is the increased occurrence of nausea and vomiting.

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.

Early Oseltamivir After Hospital Admission Is Associated With Shortened Hospitalization: A 5-Year Analysis of Oseltamivir Timing and Clinical Outcomes.

Neuraminidase inhibitors (NAIs) are the only effective therapy for influenza, but few studies have assessed the impact of early NAI therapy on clinical outcomes or the patient-level factors that determine early NAI delivery in hospitalized patients. We conducted a retrospective cohort study of all adults hospitalized in a metropolitan tertiary care hospital with confirmed influenza from April 2009 to March 2014. We performed logistic regression to determine patient-level factors that were associated with early NAI therapy. We analyzed the association of early NAI therapy with hospital lengths of stay (LOS) and in-hospital mortality rates using linear and logistic regression, respectively. In total, 699 patients were admitted with influenza during the 5 influenza seasons. Of those, 582 (83.4%) received NAI therapy; however, only 26.0% received the first dose within 6 hours of hospitalization (early NAI). Patients with diabetes mellitus or pregnancy were more likely to receive early NAI (P = .01, vs. P < .001 in those without these conditions), as were those reporting fever or myalgias at presentation (P = .002, vs. P = .005 without). Immunosuppressed patients were less likely to receive early NAI (P = .04). Early NAI was associated with shorter hospital LOS (P < .001). No patients died in the early NAI group, compared to 18 deaths in the 399 patients receiving NAI after 6 hours (4.5%) and 4 deaths in the 116 patients not receiving NAI (3.4%). Over multiple influenza seasons, early NAI therapy was associated with shorter LOS in patients admitted with influenza. This suggests that efforts should focus on facilitating earlier therapy in patients with suspected influenza.

Late diagnosis of influenza in adult patients during a seasonal outbreak.

Background/AimsDue to advances in diagnostic techniques, clinicians are more frequently performing influenza diagnostic tests and referring to their test results ahead of the administration of neuraminidase inhibitors (NAIs). To investigate the clinical significance of the time from symptom onset to laboratory diagnosis, we reviewed the clinical characteristics of adult patients with influenza who had an early laboratory diagnosis (ED) or a late laboratory diagnosis (LD) at one of four tertiary care centers during a seasonal outbreak of influenza.MethodsClinical data were collected from 1,405 adults during the 2013 to 2014 influenza season. A patient was regarded as receiving an ED or LD if he/she received an influenza diagnostic test at 0 to 1 or 4 to 7 days after symptom onset, respectively. Early NAI therapy and late NAI therapy were defined as the administration of NAI ≤ 2 or > 2 days after symptom onset, respectively.ResultsNearly half of the patients (47.0%) received an ED (n = 661), whereas 13.5% (n = 190) received a LD. Patients with a LD had initial symptoms of cough, sputum production, and dyspnea and experienced pneumonia, antibiotic therapy, hospitalization, and admission to the intensive care unit more often than those with an ED. NAI therapy and early NAI therapy were less frequent in patients with a LD than those with an ED. Of the analyzed baseline characteristics, age ≥ 50 years, influenza B infection, and diagnosis using a polymerase chain reaction test were significantly associated with a LD.ConclusionsLD was associated with inappropriate antiviral therapy and complicated presenting features in adult patients with seasonal influenza. ED of influenza should be emphasized, especially for older adults.

Benefit of Early Initiation of Neuraminidase Inhibitor Treatment to Hospitalized Patients With Avian Influenza A(H7N9) Virus.

The significance of early neuraminidase inhibitor (NAI) therapy for treating influenza A(H7N9) is currently unknown. The duration of viral shedding was monitored by reverse-transcription polymerase chain reaction after patients with confirmed H7N9 infection were admitted to the First Affiliated Hospital, Zhejiang University, during April 2013-April 2017. Indices such as the length of hospitalization and mortality were collected, and the correlation between the time of administration of NAI and the severity of disease was systematically analyzed. One hundred sixty patients with confirmed H7N9 infection were divided into 3 groups according to NAI starting time. Three of 20 (15%) patients for whom NAI was administered within 2 days died compared with 12 of 52 (23.1%) patients who received treatment within 2-5 days and 33 of 88 (37.5%) patients who were treated after 5 days (P < .05). The median durations of viral shedding from NAI therapy initiation was 4.5 days (interquartile range [IQR], 3-9 days) for patients who took antiviral medication within 2 days, which was significantly different from that for patients who took medication within 2-5 days (7.5 days [IQR, 4.25-12.75 days]) or after 5 days (7 days [IQR, 5-10 days]) (P < .05). We found that the duration of viral shedding from NAI therapy was the shortest in spring 2013 (5.5 days) and the longest in winter-spring 2016-2017 (8.5 days) (P < .05), showing a prolonged trend. Early NAI therapy within 2 days of illness shortened the duration of viral shedding and improved survival in patients with H7N9 viral infection.

Assessing the oseltamivir-induced resistance risk and implications for influenza infection control strategies.

BackgroundOseltamivir-resistant mutants with higher drug resistance rates and low trans-mission fitness costs have not accounted for influenza (sub)type viruses. Predicting the impacts of neuraminidase inhibitor therapy on infection rates and transmission of drug-resistant viral strains requires further investigation.ObjectivesThe purpose of this study was to assess the potential risk of oseltamivir-induced resistance for influenza A (H1N1) and A (H3N2) viruses.Materials and methodsAn immune-response-based virus dynamic model was used to best fit the oseltamivir-resistant A (H1N1) and A (H3N2) infection data. A probabilistic risk assessment model was developed by incorporating branching process-derived probability distribution of resistance to estimate oseltamivir-induced resistance risk.ResultsMutation rate and sensitive strain number were key determinants in assessing resistance risk. By increasing immune response, antiviral efficacy, and fitness cost, the spread of resistant strains for A (H1N1) and A (H3N2) were greatly decreased. Probability of resistance depends most strongly on the sensitive strain number described by a Poisson model. Risk of oseltamivir-induced resistance increased with increasing the mutation rate for A (H1N1) only. The ≥50% of resistance risk induced by A (H1N1) and A (H3N2) sensitive infected cells were 0.4 (95% CI: 0.28–0.43) and 0.95 (95% CI 0.93–0.99) at a mutation rate of 10−6, respectively. Antiviral drugs must be administrated within 1–1.5 days for A (H1N1) and 2–2.5 days for A (H3N2) virus infections to limit viral production.ConclusionProbabilistic risk assessment of antiviral drug-induced resistance is crucial in the decision-making process for preventing influenza virus infections.

Early administration of neuraminidase inhibitors in adult patients hospitalized for influenza does not benefit survival: a retrospective cohort study

The administration of neuraminidase inhibitors (NAIs) within 2days after the onset of symptoms (early NAI therapy) has been shown to reduce mortality in adult patients with severe influenza. However, there is no sufficiently solid evidence supporting the effectiveness of early NAI therapy on mortality. We reviewed the clinical data from 506 adult patients who were hospitalized for influenza between March 2010 and March 2014, to investigate the impact of early NAI therapy on mortality. Nearly one-third of the study patients were infected with influenza B (influenza A, influenza B, and co-infection of both in 68.8%, 28.1%, and 3.2%, respectively), and were diagnosed using the polymerase chain reaction (PCR) method (33.6%). Less than half (233, 46.0%) had received early NAI therapy. Patients with early NAI therapy were admitted to the hospital earlier, more frequently infected with influenza A, and more frequently diagnosed using rapid influenza detection tests compared to those without early NAI therapy. Although patients without early NAI therapy presented with more serious clinical manifestations, such as an initial symptom of dyspnea, pneumonia, and intensive care unit admission, than those with early NAI therapy, the in-hospital mortality of the former (2.9%, 8/273) did not differ from that of the latter (3.4%, 8/233) (p=0.75). We did not find a reduction in mortality associated with early NAI therapy in adult patients hospitalized for influenza. Further clinical studies including a large number of influenza B-infected patients with virus identification using PCR methodology rather than viral culture may be required to confirm the beneficial impact of early NAI therapy on mortality.

Effects of corticosteroid and neuraminidase inhibitors on survival in patients with respiratory distress induced by influenza virus.

Neuraminidase inhibitors (NAIs) including oseltamivir and peramivir are used for influenza treatment. A systemic corticosteroid is usually administrated for acute respiratory distress syndrome. The aim of this study was to investigate the effect of a systemic corticosteroid and its interaction with NAIs in patients with influenza infection and respiratory distress. A retrospective survey of hospitalized patients infected with influenza from January 2012 to May 2014 was conducted in a medical center in Taiwan. Eighty-six patients were hospitalized during the study period. Forty-eight patients had respiratory distress and 39 of them (81.3%, 39/48) were supported by a mechanical ventilator. All patients with respiratory distress received oseltamivir; 60.4% (29/48) and 31.3% (15/48) of them received a corticosteroid and salvage intravenous peramivir, respectively. All-cause mortality was 29.1% (14/48), 20% (3/15), and 31% (9/29) in patients with respiratory distress, patients who received salvage peramivir, and patients who received a systemic corticosteroid, respectively. Salvage peramivir seemed to improve prognosis in patients with H1pdm09 or type B virus infection and respiratory distress (p=0.05). Early initiating corticosteroid had a worse prognosis than initiation after 72 hours of NAI treatment (p=0.024). In particular, a systemic corticosteroid seemed to lead to a shorter survival time in patients with chronic lung disease (p=0.05). Salvage peramivir provided a better prognosis than monotherapy with oseltamivir in patients who were infected with H1pdm09 or type B virus and who developed respiratory distress. A systemic corticosteroid should be administered after initiating NAI therapy, especially in patients with chronic lung disease.

Neuraminidase inhibitor therapy in a military population

BackgroundAlthough neuraminidase inhibitors (NI) are the mainstay of treatment for influenza infection, prescribing practice for these agents is not well described. Additionally, benefit is contested. ObjectivesWe examined provider prescriptions of NI during the 2009 pandemic and post-pandemic periods. We also evaluated the effectiveness of NI in reducing severity of influenza infection. Study designData on NI prescription and severity of influenza infection were compiled in healthy pediatric and adult beneficiaries enrolled in a prospective study of influenza like illness conducted at five military medical centers over five years. Subjects underwent nasal swabs to determine viral etiology of their infection. Demographic, medication and severity data were collected. Subjects with positive influenza were included. ResultsTwo hundred sixty three subjects were influenza positive [38% [H1N1] pdm09, 38.4% H3N2, and 20.5% B); 23.9% were treated with NI. NI were initiated within 48h in 63% of treated subjects. Although NI use increased over the five years of the study, early use declined. Most measures for severity of illness were not significantly reduced with NI; adults treated within 48h had only a modest reduction in duration and severity of some of their symptoms. ConclusionsNI use in our population is increasing, but early use is not. NI use resulted in no reduction in complications of illness. Resolution of symptoms and reduction in severity of some symptoms were slightly better in adults who were treated early. These modest benefits do not support routine treatment with NI in otherwise healthy individuals with influenza.

Prospective Cohort Study Comparing Seasonal and H1N1(2009) Pandemic Influenza Virus Illnesses in HIV-infected Children During 2009

A cohort of 410 young HIV-infected children was prospectively investigated for seasonal and A(H1N1p)2009 influenza virus illness during 2009. The incidence of confirmed illness due to seasonal influenza was 3-fold greater than A(H1N1p)2009 (0.7 vs. 0.2 per 100 child-weeks, respectively; P = 0.0001), and the clinical presentations were similar. Illnesses due to seasonal and A(H1N1p)2009 influenza were self-limiting without neuraminidase inhibitor therapy.

Serum immunoglobulin G subclass levels and estimated clinical severity caused by possible influenza A (H1N1) pdm 2009 infection

The clinical severity of the 2009 pandemic H1N1 influenza (H1N1 pdm09) was thought to be related to the difference between the amount of viral load and condition of the host immune response. We investigated the role of serum levels of IgG and its subclasses in clinical severity using the data from 45 child inpatients suffering from bronchitis or mild pneumonia caused by possible H1N1 pdm09 (pH1N1 pdm09) infection. After selecting parameters for serum IgG subclasses and logarithmically transformed urinary beta-2 microglobulin/creatinine (b2MG/Cr) values and admission duration, we performed path analysis using a mean covariance structure equation analysis to investigate the relationship between the clinical severity and the foregoing selected parameters. Total path analyses using a Bayesian method revealed that the estimated clinical severity caused by pH1N1 pdm09 was positively associated with maximal respiration rates, admission duration, and log urinary b2MG/Cr levels, whereas negatively associated with serum IgG, IgG1, IgG2, and IgG3 levels, duration of neuraminidase inhibitor therapy in outpatient clinics, and age. Serum IgG and its subclasses (IgG1-IgG3) reduced estimated clinical severity in children with pH1N1 pdm09 infection.

The Emergency Use Authorization of Peramivir IV: A View from the Manufacturer

The 2009 H1N1 influenza pandemic prompted the US Food and Drug Administration (FDA) to issue an emergency use authorization (EUA) for the intravenous antiviral peramivir, an unapproved neuraminidase inhibitor (NAI) currently under development. Peramivir use was limited to patients for whom other NAI therapy had failed or in whom oral or inhalational drug absorption was believed to be unreliable. This introduced a patient selection bias that precluded safety and efficacy assessment. Despite the challenges and risks, there was a compelling public health need for an intravenous agent during the 2009 H1N1 pandemic.

Influence of age on symptoms and laboratory findings at presentation in patients with influenza-associated pneumonia

Influenza virus infection is a major respiratory infectious disease that generally induces pneumonia. The clinical manifestations of influenza virus infection and community-acquired pneumonia (CAP) differ between elderly persons and younger adults. To determine the clinical features of influenza-associated pneumonia, we studied 21 adult patients with influenza-associated pneumonia, as indicated by positive test results for influenza virus antigen. At presentation, the higher-age patients (≥75 years; n=12) with influenza-associated pneumonia had lower body temperature than did the lower-age (<75 years) patients (n=9). Conversely, the laboratory data indicated significantly higher C-reactive protein (CRP) concentration in higher-age patients than that in lower-age patients. None of the 18 patients undergoing neuraminidase inhibitor therapy died, but two of three patients who did not receive this therapy died from complications of advanced pneumonia. In this study, vaccination did not appear to be an important factor for prevention of pneumonia. High-age patients with CAP have lower body temperature, raising the possibility that diagnosis and treatment may be delayed in these patients. Increased CRP levels in these patients at presentation, however, could contribute to early detection of this serious pulmonary complication.

Neuraminidase Inhibitors Improve Outcome of Patients with Leukemia and Influenza: An Observational Study

We reviewed the records of 33 patients with leukemia who experienced influenza during the period from October 2000 to March 2004. Three (38%) of the 8 patients who did not receive neuraminidase inhibitor therapy and none of the 25 patients who received it died of influenza pneumonia (P=.001). The use of neuraminidase inhibitor therapy seems to improve the outcome of influenza in patients with leukemia.

COST-EFFECTIVENESS OF NEWER TREATMENT STRATEGIES FOR INFLUENZA

Smith KJ, Roberts MS. Am J Med. 2002;113:300–307 Recent advances in the diagnosis and treatment of influenza, such as rapid testing and neuraminidase inhibitor therapy, are available, but their place in clinical practice and their cost-effectiveness have not been determined. To estimate the cost-effectiveness of these newer interventions, we used a decision model that compared several influenza management strategies: no testing or treatment, amantadine or rimantadine treatment without testing, testing then amantadine or rimantadine treatment, neuraminidase inhibitor treatment without testing, or testing then neuraminidase inhibitor treatment. Antiviral therapy began within …

A population-dynamic model for evaluating the potential spread of drug-resistant influenza virus infections during community-based use of antivirals

A mathematical model of influenza transmission dynamics is used to simulate the impact of neuraminidase inhibitor therapy on infection rates and transmission of drug-resistant viral strains. The model incorporates population age structure, seasonal transmission, immunity and inclusion of elderly nursing home residents or non-residents. Key parameter values are estimated from epidemiological, clinical and experimental data. The analysis examines the factors determining the population spread of antiviral resistance, and predicts no significant transmission of neuraminidase inhibitor resistant virus. This conclusion is robust even at high therapy levels and under conservative assumptions regarding the likely frequency of transmission of resistant virus. The predicted incidence of resistance following protracted usage reflects primary drug resistance, currently estimated as approximately 2% for neuraminidase inhibitor therapy. It is also shown that until high levels of therapy are attained, early treatment of symptomatic cases is more efficient (per unit of drug) at preventing infections than prophylactic therapy.

Cost-effectiveness of newer treatment strategies for influenza

PurposeRecent advances in the diagnosis and treatment of influenza, such as rapid testing and neuraminidase inhibitor therapy, are available, but their place in clinical practice and their cost-effectiveness have not been determined. Materials and methodsTo estimate the cost-effectiveness of these newer interventions, we used a decision model that compared several influenza management strategies: no testing or treatment, amantadine or rimantadine treatment without testing, testing then amantadine or rimantadine treatment, neuraminidase inhibitor treatment without testing, or testing then neuraminidase inhibitor treatment. Antiviral therapy began within 48 hours in febrile patients with characteristic symptoms of influenza. We assumed that antiviral treatment did not change rates of influenza complication or mortality, and chose parameter values in the baseline analysis to bias slightly against antiviral treatment and toward testing strategies. ResultsIn the baseline analysis, testing strategies are more expensive and less effective than treatment strategies. Amantadine costs $9.06 per illness day avoided or $11.60 per quality-adjusted day gained. Compared with amantadine, zanamivir costs $198 per illness day avoided or $185 per quality-adjusted day gained, whereas oseltamivir costs $252 per illness day avoided or $235 per quality-adjusted day gained. In elderly patients who require reduced dosage, rimantadine costs $128 per quality-adjusted day gained compared with amantadine. In younger patients, amantadine is favored if the likelihood of influenza A is >67%; otherwise, neuraminidase inhibitors are favored. Testing strategies are more costly and less effective when the influenza probability is >30%. No testing or treatment is favored if the influenza probability is <32% and the influenza utility is >0.77. In elderly patients, amantadine is favored over rimantadine if the utility of medication side effects is >0.94. ConclusionAntiviral treatment of influenza without rapid testing is reasonable economically in febrile patients with typical symptoms during influenza season. The choice of antiviral agent depends on age, the likelihood of influenza A, and the willingness to pay per quality-adjusted day gained.

Clinical evaluation of an immunochromatography test for rapid diagnosis of influenza

We evaluated a rapid diagnostic kit that detects influenza type A and B viral antigens by immunochromatography, Quick Vue Influenza Test (Quidel Corp., San Diego, CA, USA), with 425 specimens collected from patients with influenza-like symptoms at three hospitals between January and March 2001. The specimens included 184 nasal aspirates, 140 nasal swabs, and 101 throat swabs. The test correctly identified 179 of the 204 culture positive specimens and 203 of the 221 culture negative specimens; the sensitivity and specificity compared with the culture were 87.7% and 91.9%, respectively. The sensitivity of the test was 92.6% (112/121) for nasal aspirates, 83.7% (41/49) for nasal swabs, and 76.5% (26/34) for throat swabs, which is similar to the results for conventional rapid enzyme immunoassay kits for influenza virus infection. The sensitivity and specificity of the QuickVue Influenza Test were equivalent to those of Flu OIA (BioStar, Inc., Boulder, CO, USA), with the agreement of 84.2%. Although the QuickVue Influenza Test does not differentiate between influenza A and B viruses, the easy-to-use kit detects both types in the physician's office, allowing physicians to make a decision on prescription of neuraminidase inhibitor therapy during the initial visit.