Influenza Signs and Symptoms and the Role of Laboratory Diagnostics
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- Signos y síntomas
- Procedimientos de diagnóstico por laboratorio
- Cultivo viral
- RIDTS
- Pruebas serológicas
Signos y síntomas
Influenza illness can include any or all of these signs and symptoms: fever, muscle aches, headache, lack of energy, dry cough, sore throat, nasal congestion, and possibly runny nose. La fiebre y los dolores corporales pueden durar hasta 3-5 días y la tos y la falta de energía podría durar por 2 semanas o más. Influenza can be difficult to diagnose based on clinical signs and symptoms alone because influenza illness can be similar to illness caused by other infectious agents including, but not limited to,Mycoplasma pneumoniae, adenovirus, respiratory syncytial virus, rhinovirus, parainfluenza viruses, andLegionella spp.
El tratamiento adecuado de pacientes con enfermedades respiratorias depende del diagnóstico preciso y oportuno. El diagnóstico temprano de influenza puede reducir el uso inapropiado de antibióticos y brindar la opción de usar la terapia antiviral. However, because certain bacterial infections can produce signs and symptoms similar to influenza, bacterial infections should be considered and appropriately treated, if suspected. Además, las infecciones bacterianas pueden manifestarse como una complicación de la influenza.
La información de vigilancia de la influenza y las pruebas de diagnóstico pueden ayudar a los criterios clínicos y a orientar las decisiones de tratamiento. The accuracy of clinical diagnosis of influenza on the basis of signs and symptoms alone is limited because symptoms from illness caused by other pathogens can overlap considerably with influenza. Influenza surveillance by state and local health departments and CDC can provide information regarding the prevalence of influenza A and B viruses in the community. Surveillance can also identify the predominant circulating types, influenza A virus subtypes, and strains of influenza viruses.
ArribaProcedimientos de diagnóstico por laboratorio
Una serie de pruebas pueden ayudar al diagnóstico de la influenza (ver tabla). Pero no es necesario realizar las pruebas en todos los pacientes. For individual patients, tests are most useful when they are likely to yield clinically useful results that will help with diagnosis and treatment decisions. During a respiratory illness outbreak in a closed setting (e.g., hospitals, nursing home, cruise ship, boarding school, summer camp) however, testing for influenza can be very helpful in determining if influenza is the cause of the outbreak.
Las muestras respiratorias preferenciales para la prueba de la influenza incluyen el hisopado nasofaríngeo o nasal y el lavado nasal o aspirado, dependiendo del tipo de prueba que se utilice. (ver tabla). Las muestras deben tomarse dentro de los primeros 4 días de la enfermedad. Las pruebas de diagnóstico rápido de la influenza arrojan resultados dentro de los 20 minutos o menos; el cultivo viral proporciona resultados en 3 a 10 días. La mayoría de las pruebas de diagnóstico rápido de la influenza que se pueden realizar en el consultorio del médico tienen una sensibilidad de alrededor del 50 a 70% para detectar la influenza y aproximadamente más del 90% para casos específicos. Por lo tanto, los resultados negativos falsos son más comunes que los resultados positivos falsos, especialmente durante el pico máximo de la actividad.
Diagnostic tests available for influenza include viral culture, serology, rapid antigen testing, reverse transcription polymerase chain reaction (RT-PCR), immunofluorescence assays, and rapid molecular assays. Sensitivity and specificity of any test for influenza might vary by the laboratory that performs the test, the type of test used, the time from illness onset to specimen collection, and the type of specimen tested. Among respiratory specimens for viral isolation or rapid detection of human influenza viruses, nasopharyngeal specimens typically have higher yield than nasal or throat swab specimens. Como con cualquier prueba de diagnóstico, los resultados deben evaluarse en el contexto de otra información clínica y epidemiológica disponible para los proveedores de servicios de salud.
ArribaCultivo viral
A pesar de la disponibilidad de las pruebas de diagnóstico rápidas, la recolección de muestras clínicas para el cultivo viral es fundamental, debido a que solo el aislamiento del cultivo puede proporcionar información específica con respecto a las cepas que están en circulación y a los subtipos de virus de influenza. This information is needed to compare current circulating influenza virus strains with vaccine strains, to guide decisions regarding influenza antiviral treatment and chemoprophylaxis, and to formulate vaccine for the coming year. Virus isolates also are needed to monitor the emergence of antiviral resistance and the emergence of novel influenza A viruses that might pose a pandemic threat.
Cuando se sospecha de casos de influenza durante los brotes de la enfermedad respiratoria, deben evaluarse algunas muestras respiratorias mediante pruebas de diagnóstico rápido de la influenza y de cultivo viral. The collection of some respiratory samples for viral culture is essential for determining the influenza A subtypes and influenza A and B virus strains causing illness, and for surveillance of new strains that may need to be included in the next year's influenza vaccine. Durante los brotes de enfermedades similares a la influenza, el cultivo viral también puede ayudar a identificar otras causas de enfermedades.
ArribaRIDTS
Las pruebas de diagnóstico rápido de la influenza comercialmente disponibles pueden detectar los virus de influenza en 20 minutos. Some tests are CLIA-waived and approved for use in any outpatient setting, whereas others must be used in a moderately complex clinical laboratory. Estas pruebas de diagnóstico rápido de la influenza difieren en los tipos de virus de la influenza que pueden detectar y en el hecho de que si pueden o no distinguir entre un tipo de influenza y otro. Las diferentes pruebas pueden detectar: 1) los virus de la influenza A únicamente; 2) tanto los virus de la influenza A como la B, pero sin diferenciar los dos tipos; o 3) tanto la influenza A como la B y diferenciar las dos.
None of the rapid influenza diagnostic tests provide any information about influenza A virus subtypes. Los tipos de muestras aceptables para el uso (por ej., de garganta, nasofaríngeas o aspirado, hisopados o lavados) también varían según la prueba. The specificity and, in particular, the sensitivity of rapid influenza diagnostic tests are lower than for viral culture and RT-PCR and vary by test. Because of the lower sensitivity of the rapid influenza diagnostic tests, physicians should consider confirming negative tests with RT-PCR, viral culture or other means, especially in hospitalized patients or during suspected institutional influenza outbreaks because of the possibility of false-negative rapid test results, especially during periods of peak community influenza activity. Por el contrario, los resultados falsos-positivos de las pruebas rápidas son menos probables, pero pueden surgir durante períodos de baja actividad de la influenza. Por lo tanto, cuando se interpreten los resultados de una prueba de diagnóstico rápido de influenza, los médicos deben considerar los valores de predicción positivos y negativos de la prueba en el contexto del nivel de actividad de la influenza en la comunidad. Se deben consultar las instrucciones de empleo y el laboratorio que realiza la prueba para obtener más detalles con respecto al uso de las pruebas de diagnóstico rápido de la influenza.
ArribaPruebas serológicas
La prueba serológica rutinaria para la influenza que requiere muestras pareadas de suero agudo y convaleciente, no arroja resultados que ayudan en la toma de decisiones, está sólo disponible en un número limitado de laboratorios de salud pública o de investigación y generalmente no se recomienda, excepto para investigaciones de estudio y salud pública. Serological testing results for antibodies to human influenza viruses on a single serum specimen is not interpretable and is not recommended.
Tabla de diagnóstico de influenza
ArribaDescargo de responsabilidad: Es posible que en este sitio encuentre algunos enlaces que le lleven a contenido disponible sólo en inglés. Además, el contenido que se ha traducido del inglés se actualiza a menudo, lo cual puede causar la aparición temporal de algunas partes en ese idioma hasta que se termine de traducir (generalmente en 24 horas). Llame al 1-800-CDC-INFO si tiene preguntas sobre la influenza estacional, cuyas respuestas no ha encontrado en este sitio. Agradecemos su paciencia
Influenza Signs and Symptoms and the Role of Laboratory Diagnostics | Health Professionals | Seasonal Influenza (Flu)
Influenza Signs and Symptoms and the Role of Laboratory Diagnostics
On this Page
Signs and Symptoms
Influenza illness can include any or all of these signs and symptoms: fever, muscle aches, headache, lack of energy, dry cough, sore throat, nasal congestion, and possibly runny nose. The fever and body aches can last 3-5 days and the cough and lack of energy may last for 2 or more weeks. Influenza can be difficult to diagnose based on clinical signs and symptoms alone because influenza illness can be similar to illness caused by other infectious agents including, but not limited to, Mycoplasma pneumoniae, adenovirus, respiratory syncytial virus, rhinovirus, parainfluenza viruses, and Legionella spp.
Appropriate treatment of patients with respiratory illness depends on accurate and timely diagnosis. Early diagnosis of influenza can reduce the inappropriate use of antibiotics and provide the option of using antiviral therapy. However, because certain bacterial infections can produce signs and symptoms similar to influenza, bacterial infections should be considered and appropriately treated, if suspected. In addition, bacterial infections can occur as a complication of influenza.
Influenza surveillance information and diagnostic testing can aid clinical judgment and help guide treatment decisions. The accuracy of clinical diagnosis of influenza on the basis of signs and symptoms alone is limited because symptoms from illness caused by other pathogens can overlap considerably with influenza. Influenza surveillance by state and local health departments and CDC can provide information regarding the prevalence of influenza A and B viruses in the community. Surveillance can also identify the predominant circulating types, influenza A virus subtypes, and strains of influenza viruses.
Top of PageLaboratory Diagnostic Procedures
A number of tests can help in the diagnosis of influenza (see table). But, tests do not need to be done on all patients. For individual patients, tests are most useful when they are likely to yield clinically useful results that will help with diagnosis and treatment decisions. During a respiratory illness outbreak in a closed setting (e.g., hospitals, nursing home, cruise ship, boarding school, summer camp) however, testing for influenza can be very helpful in determining if influenza is the cause of the outbreak.
Preferred respiratory samples for influenza testing include nasopharyngeal or nasal swab, and nasal wash or aspirate, depending on which type of test is used (see table). Samples should be collected within the first 4 days of illness. Rapid influenza diagnostic tests provide results within 20 minutes or less; viral culture provides results in 3-10 days. Most of the rapid influenza diagnostic tests that can be done in a physician’s office are approximately 50-70% sensitive for detecting influenza and approximately greater than 90% specific. Therefore, false negative results are more common than false positive results, especially during peak influenza activity.
Diagnostic tests available for influenza include viral culture, serology, rapid antigen testing, reverse transcription polymerase chain reaction (RT-PCR), immunofluorescence assays, and rapid molecular assays. Sensitivity and specificity of any test for influenza might vary by the laboratory that performs the test, the type of test used, the time from illness onset to specimen collection, and the type of specimen tested. Among respiratory specimens for viral isolation or rapid detection of human influenza viruses, nasopharyngeal specimens typically have higher yield than nasal or throat swab specimens. As with any diagnostic test, results should be evaluated in the context of other clinical and epidemiologic information available to health-care providers.
Top of PageViral Culture
Despite the availability of rapid influenza diagnostic tests, collecting clinical specimens for viral culture is critical, because only culture isolates can provide specific information regarding circulating strains and subtypes of influenza viruses. This information is needed to compare current circulating influenza virus strains with vaccine strains, to guide decisions regarding influenza antiviral treatment and chemoprophylaxis, and to formulate vaccine for the coming year. Virus isolates also are needed to monitor the emergence of antiviral resistance and the emergence of novel influenza A viruses that might pose a pandemic threat.
During outbreaks of respiratory illness when influenza is suspected, some respiratory samples should be tested by both rapid influenza diagnostic tests and by viral culture. The collection of some respiratory samples for viral culture is essential for determining the influenza A subtypes and influenza A and B virus strains causing illness, and for surveillance of new strains that may need to be included in the next year’s influenza vaccine. During outbreaks of influenza-like illness, viral culture also can help identify other causes of illness.
Top of PageRIDTS
Commercial rapid influenza diagnostic tests are available that can detect influenza viruses within 20 minutes. Some tests are CLIA-waived and approved for use in any outpatient setting, whereas others must be used in a moderately complex clinical laboratory. These rapid influenza diagnostic tests differ in the types of influenza viruses they can detect and whether they can distinguish between influenza types. Different tests can detect 1) only influenza A viruses; 2) both influenza A and B viruses, but not distinguish between the two types; or 3) both influenza A and B and distinguish between the two.
None of the rapid influenza diagnostic tests provide any information about influenza A virus subtypes. The types of specimens acceptable for use (i.e., throat, nasopharyngeal, or nasal aspirates, swabs, or washes) also vary by test. The specificity and, in particular, the sensitivity of rapid influenza diagnostic tests are lower than for viral culture and RT-PCR and vary by test. Because of the lower sensitivity of the rapid influenza diagnostic tests, physicians should consider confirming negative tests with RT-PCR, viral culture or other means, especially in hospitalized patients or during suspected institutional influenza outbreaks because of the possibility of false-negative rapid test results, especially during periods of peak community influenza activity. In contrast, false-positive rapid test results are less likely, but can occur during periods of low influenza activity. Therefore, when interpreting results of a rapid influenza diagnostic test, physicians should consider the positive and negative predictive values of the test in the context of the level of influenza activity in their community. Package inserts and the laboratory performing the test should be consulted for more details regarding use of rapid influenza diagnostic tests.
Top of PageSerologic Testing
Routine serological testing for influenza requires paired acute and convalescent sera, does not provide results to help with clinical decision-making, is only available at a limited number of public health or research laboratories and is not generally recommended, except for research and public health investigations. Serological testing results for antibodies to human influenza viruses on a single serum specimen is not interpretable and is not recommended.
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