Utilidad del test de Utilidad del test de diagnóstico rápido en diagnóstico rápido en faringoamigdalitis en faringoamigdalitis en

las consultas de las consultas de atencion primariaatencion primaria

Marta Ocampo FontangordoMarta Ocampo FontangordoR IV MFyC - CS MonteporreiroR IV MFyC - CS Monteporreiro

06 Junio 2008 06 Junio 2008

FaringoamigdalitisFaringoamigdalitis Uno de los procesos más frecuentes en APUno de los procesos más frecuentes en AP Variable según edad, etiología y tipo clínico.Variable según edad, etiología y tipo clínico. Origen víricoOrigen vírico: 70% de las ocasiones: 70% de las ocasiones Streptococo del grupo AStreptococo del grupo A se aísla en 10-20% de se aísla en 10-20% de

casoscasos En la práctica médica preocupa especialmente la En la práctica médica preocupa especialmente la

etiología por etiología por S. pyogenesS. pyogenes, por lo que el , por lo que el diagnóstico de rutina se encamina a confirmar o diagnóstico de rutina se encamina a confirmar o descartar el citado microorganismo.descartar el citado microorganismo.

El tratamiento antimicrobiano debe hacerse solo El tratamiento antimicrobiano debe hacerse solo bajo sospechas fundadas de etiología bacteriana.bajo sospechas fundadas de etiología bacteriana.

El tratamiento con penicilina sigue siendo el de El tratamiento con penicilina sigue siendo el de elección en los procesos por elección en los procesos por S. pyogenes.S. pyogenes.

EpidemiologíaEpidemiología España:España:

4 millones consultas/años (20% de las consultas pediátricas)4 millones consultas/años (20% de las consultas pediátricas) Calculan 16 millones de casos anualesCalculan 16 millones de casos anuales De ellos 50 mil por De ellos 50 mil por Streptococcus pyogenes (0.31%/anual)Streptococcus pyogenes (0.31%/anual)

3º cuadro respiratorio (resfriado 3º cuadro respiratorio (resfriado común>traqueobronquitis aguda)común>traqueobronquitis aguda)

15- 20% de todos los casos Infecciones respiratorias 15- 20% de todos los casos Infecciones respiratorias 36-55%% de todas las prescripciones de antibióticos 36-55%% de todas las prescripciones de antibióticos

MF sospechan una etiología bacteriana en el 60% de los casosMF sospechan una etiología bacteriana en el 60% de los casos Administran antibióticos en el 85% de los enfermos (98% en pultácea)Administran antibióticos en el 85% de los enfermos (98% en pultácea)

Edad mayor incidencia: 3 y 15 años (sin predilección Edad mayor incidencia: 3 y 15 años (sin predilección sexos)sexos)

Adulto causa frecuente de consulta absentismo laboral Adulto causa frecuente de consulta absentismo laboral (hasta 6,5 días IT) (hasta 6,5 días IT)

Meses fríos del añoMeses fríos del año Rhinovirus y otros virus respiratorios: finalde la primaveraRhinovirus y otros virus respiratorios: finalde la primavera Adenovirus: Principio del veranoAdenovirus: Principio del verano Streptocócicas: invierno y principiosde primaveraStreptocócicas: invierno y principiosde primavera

FaringoamigdalitisFaringoamigdalitis Faringitis agudas inespecíficasFaringitis agudas inespecíficas

Catarrales ,muy eritematosas, "rojas “Catarrales ,muy eritematosas, "rojas “ Eritemato-supurativas o " blancas “Eritemato-supurativas o " blancas “

Faringitis agudas específicas (manifestaciones Faringitis agudas específicas (manifestaciones faríngeas de infecciones Sistémicas)faríngeas de infecciones Sistémicas) Diftérica por Corynebacterium diphteriaeDiftérica por Corynebacterium diphteriae Fuso-espirilar de Plaut-Vincent por Fuso-espirilar de Plaut-Vincent por Fusobacterium Fusobacterium

necrophorumnecrophorum Neisseria gonorrhoeaeNeisseria gonorrhoeae Tularemia por Tularemia por Fran cisella tularensisFran cisella tularensis Herpangina por los virus Herpangina por los virus Cosxackie Cosxackie A y V. EchoA y V. Echo Herpética: Herpética: virus del Herpes simple o V-Zvirus del Herpes simple o V-Z Mononucleosis infecciosa por EBVMononucleosis infecciosa por EBV Candidiasis faríngeaCandidiasis faríngea

Faringitis crónica (no infecciosas)Faringitis crónica (no infecciosas)

Faringoamigdalitis. Faringoamigdalitis. EtiologíaEtiología

EtiologíaEtiología ObservacionesObservacionesVírica (60-80%) Rhinovirus (20%)

Coronavirus (5%)Adenovirus (5%)Herpes simplex 1 y 2 (2-4%)Virus parainfluenza. Virus Influenza A y B (2%)Virus Cosackie A (< 1%)Virus Epstein-Barr, Citomegalovirus (< 1%)VIH

Streptococcus grupoC y G

Algunos casos de adultos

Streptococcus Beta-hemolítico del grupo A ó pyogenes (5.10%)

< 3 años: raro3-5 años: poco frecuente 5-15: alta incidencia (30-55%) 20% de niños de 5-10 años son portadores sanosAdultos: 5-23% de aislamientos

Mycoplasma pneumoniae

adolescentes y adultos jóvenes

Anaerobios < 1%Chlamidia pneumoniae C. trachomatis

No recurrencias

ClínicaClínica

Invierno-primaveraVariableESTACIONAL

BruscoGradualINICIO

Fiebre elevadaOdinofagia importante

Fiebre leveOdinofagia leve

SÍNTOMAS

DURACIÓN: Curso breve entre 3-5 días. Amígdalas y ganglios linfáticos pueden tardar semanas en recuperarse.

Dolorosas. Aumento de tamaño

Múltiples y pequeñas o

ausentes

ADENOPATÍAS

Inflamación importante Exudado (70%)

Eritematosa Exudado (65%)

FARINGE

Cefalea, dolor abdominal, naúseas, vómitos,

exantema

Conjuntivitis, rinitis, tos,

mialgias, diarrea

OTROS SÍNTOMAS

5-15 años< 2 añosEDAD

BACTERIANAVÍRICA

Diagnóstico etiológico Diagnóstico etiológico clínicoclínico

Hasta un 30% de las faringitis de causa Hasta un 30% de las faringitis de causa bacteriana cursa sin exudado bacteriana cursa sin exudado amigdalar,amigdalar,

Un 65% de los casos de origen viral Un 65% de los casos de origen viral está presente el exudadoestá presente el exudado

Criterios de CENTOR-Criterios de CENTOR-McISAACMcISAAC

Cultivo y Test antigénico Cultivo y Test antigénico rápidorápido

Faringoamigdalitis. Criterios CentorFaringoamigdalitis. Criterios Centor (Grado recomendación B)(Grado recomendación B)

Criterios CentorCriterios Centor PuntosPuntosTemperatura > 38ºTemperatura > 38º 11

Exudado amigdalarExudado amigdalar 11

Adenopatías anteriores dolorosas e Adenopatías anteriores dolorosas e inflamadosinflamados

11

Ausencia de tosAusencia de tos 11

Edad (McISAAC)Edad (McISAAC) 3-14 años3-14 años 15-44 años15-44 años 45 años o más45 años o más

1100-1-1

Validado (McIsaac) para su utilización en niños y adultos

Faringoamigdalitis.Faringoamigdalitis.Recomendación de las guíasRecomendación de las guías

Puntuación total

Riesgo de infección estreptocócica

Estrategia sugerida

01

1 – 2,5%5 – 10%

No test adicional ni ATB

23

11 – 17%28 – 35%

Cultivo o test antigénico y ATB si positividad

≥4 51 – 53% Tratamiento ATB empírico

McIsaac WJ. CMAJ. 2000;163:811-5.

Cultivo faríngeoCultivo faríngeo Patrón oro para el diagnóstico. Correctamente Patrón oro para el diagnóstico. Correctamente

realizado (frotando la superficie de ambas realizado (frotando la superficie de ambas amigdalas o las fosas amigdalares y la faringe amigdalas o las fosas amigdalares y la faringe posterior)posterior)

Tiene una sensibilidad superior al 90% para Tiene una sensibilidad superior al 90% para detectar S. pyogenes y un resultado negativo detectar S. pyogenes y un resultado negativo prácticamente descarta la implicación de esta prácticamente descarta la implicación de esta bacteria.bacteria.

Inconveniente:Inconveniente: La información se demora 48 horasLa información se demora 48 horas Prevalencia de portadores asintomáticos alto en Prevalencia de portadores asintomáticos alto en

niños. no permite distinguir entre infección aguda niños. no permite distinguir entre infección aguda y estado de portadory estado de portador

Test antigénico rápidoTest antigénico rápido

Se completa en 5 minutosSe completa en 5 minutos Especificidad ≥ 95%Especificidad ≥ 95% sensibilidad 80-96%sensibilidad 80-96% Adultos, un test rápido negativo se Adultos, un test rápido negativo se

considera evidencia suficiente contra la considera evidencia suficiente contra la implicación de implicación de S. pyogenesS. pyogenes (baja (baja prevalencia de este agente)prevalencia de este agente)

Inconveniente:Inconveniente: No distingue entre infección aguda y estado No distingue entre infección aguda y estado

de portador, por eso en niños < 15 años de portador, por eso en niños < 15 años algunos autores recomiendan ante la algunos autores recomiendan ante la negatividad practicar cultivonegatividad practicar cultivo

Test antigénico rápido

Validez de la evaluación clínica y la Validez de la evaluación clínica y la prueba StrepA en pacientes con prueba StrepA en pacientes con

amigdalitisamigdalitis Evaluación clínica:Evaluación clínica:

Sensibilidad 49%Sensibilidad 49% Especificidad 81%Especificidad 81% Riesgo de un resultado Riesgo de un resultado

falso: falso: - Falso negativo: 51%.- Falso negativo: 51%.

- Falso positivo: 19%.- Falso positivo: 19%.

Exact StrepA DipstickExact StrepA Dipstick Sensibilidad 80-90%.Sensibilidad 80-90%. Especificidad 98%.Especificidad 98%. Riesgo de un resultado Riesgo de un resultado

falso: falso: - Falso negativo: 5%.- Falso negativo: 5%.

- Falso positivo: 2%.- Falso positivo: 2%.

Andersen et al. Potential of antigen detection tests. BMJ 1995

IDSA, ACP: no iniciar antibioterapia hasta confirmación microbiológica (cultivo o test de detección antigénica)

¿¿Necesidad de pruebas de diagnóstico Necesidad de pruebas de diagnóstico rápido?rápido?

Situaciones clínico-diagnósticoSituaciones clínico-diagnóstico Uso innecesario de Uso innecesario de tratamiento antibióticotratamiento antibiótico

Tratamiento empírico con con Tratamiento empírico con con puntuación ≥ 3 (sin pruebas)puntuación ≥ 3 (sin pruebas)

44-60 %44-60 %

Criterios de Centor ≥ 2Criterios de Centor ≥ 2++

Test Antigénico rápido/CultivoTest Antigénico rápido/Cultivo

3%3%

Faringoamidalitis. Faringoamidalitis. Estrategia diagnóstica-Estrategia diagnóstica-

terapéuticaterapéutica Los pocos pacientes con complicaciones pueden Los pocos pacientes con complicaciones pueden

ser ser tratadostratados cuando esto ocurra cuando esto ocurra Un retraso del tratamiento con ATB hasta 9 días Un retraso del tratamiento con ATB hasta 9 días

sigue siendo eficaz en la prevención de la fiebre sigue siendo eficaz en la prevención de la fiebre reumáticareumática

La efectividad del tratamiento ATB puede La efectividad del tratamiento ATB puede mejorar si lo utilizamos en pacientes con mayor mejorar si lo utilizamos en pacientes con mayor riesgo de infección por S. pyógenesriesgo de infección por S. pyógenes Predicción clínica (Criterios Centor)Predicción clínica (Criterios Centor) Test antigénico rápidoTest antigénico rápido Cultivo de frotis faríngeo Cultivo de frotis faríngeo

¿Son los Streptotest útiles para ¿Son los Streptotest útiles para confirmar el diagnóstico de faringitis confirmar el diagnóstico de faringitis por Streptococo beta-hemolitico tipo por Streptococo beta-hemolitico tipo A en la consulta de Atención A en la consulta de Atención Primaria?Primaria?

¿Permiten la toma efectiva de ¿Permiten la toma efectiva de decisiones clínicas sin esperar al decisiones clínicas sin esperar al cultivo faringeo?cultivo faringeo?

Recursos de ayuda para la toma de decisiones en el punto de atención Guías de Práctica Clínica (GPC) Informes de Agencia de Evaluación Revisiones Sistemáticas (RS) Revistas secundarías o de resúmenes Temas valorados críticamente-CAT Metabuscadores Otros documentos: Consensos, libros electrónicos, etc.

Fuentes consultadasFuentes consultadas CKS-Clinical Knowledge del NHS BritanicoCKS-Clinical Knowledge del NHS Britanicohttp://www.cks.library.nhs.uk/clinical_topicshttp://www.cks.library.nhs.uk/clinical_topics National Guideline ClearinghouseNational Guideline Clearinghouse

http://http://www.guideline.govwww.guideline.gov// Guidelines Finder de la  National electronic Guidelines Finder de la  National electronic

Library for Health del NHS británicoLibrary for Health del NHS británicohttp://www.library.nhs.uk/guidelinesfinder/http://www.library.nhs.uk/guidelinesfinder/

CMA Infobase CMA Infobase http://mdm.ca/cpgsnew/cpgs/index.asp http://mdm.ca/cpgsnew/cpgs/index.asp

OtrosOtros

Sore throat - acute - Making a diagnosis. Streptococcal infection (last revised in April 2008) Rapid antigen tests: Rapid antigen tests detect the presence of group A streptococcal antigen on a throat swab and produce results within a few minutes. However, they have poor sensitivity and make little impact on prescribing decisions [SIGN, 1999; Cooper et al, 2001].

Throat swabs: Throat swabs cannot differentiate between infection and carriage, they have poor sensitivity, results take up to 48 hours to be reported, and the analysis is relatively expensive [Little and Williamson, 1996; MeReC, 1999; SIGN, 1999]. The results of throat swabs vary according to technique, culture site, and culture conditions [Cooper et al, 2001]. Group A beta-haemolytic streptococcus (GABHS) can be isolated from up to 30% of people presenting with sore throat [Bisno, 2005]. However, figures for asymptomatic carriage range from 6% to 40% [Little and Williamson, 1996]. Carriers have low infectivity and are not at risk of developing complications. Swabs may be useful in high-risk groups, to guide the choice of treatment if treatment failure occurs (see the section on Choice of antibiotic).

Infectious disease. Laboratory medicine practice guidelines: evidence-based practice

for point-of-care testing. Guideline 114Guideline 114. . Rapid tests for diagnosis of GAS Rapid tests for diagnosis of GAS pharyngitis in general provide clinically pharyngitis in general provide clinically useful, financially justified results; these useful, financially justified results; these tests also have utility for testing tests also have utility for testing nonpharyngeal specimens. The nonpharyngeal specimens. The recommendation of the American Academy recommendation of the American Academy of Pediatrics to confirm negative rapid of Pediatrics to confirm negative rapid GAS antigen detection results of GAS antigen detection results of pharyngeal specimens from children pharyngeal specimens from children should be followed; the Infectious Diseases should be followed; the Infectious Diseases Society of America recommendation to Society of America recommendation to perform laboratory tests (either throat perform laboratory tests (either throat culture or rapid antigen detection) on culture or rapid antigen detection) on specimens from adults with clinical specimens from adults with clinical evidence of pharyngitis should be followed. evidence of pharyngitis should be followed.

Strength/consensus of Strength/consensus of recommendation: Arecommendation: A Level of evidence: IIILevel of evidence: III

BIBLIOGRAPHIC SOURCE(S) Campbell S, Campos J, Hall GS, LeBar WD, Greene W, Roush D, Rudrik JT, Russell B, Sautter R. Infectious disease. In: Laboratory medicine practice guidelines: evidence-based practice for point-of-care testing. Washington (DC): National Academy of Clinical Biochemistry (NACB); 2006. p. 76-94. [195 references]

Sore throat and Sore throat and tonsillitistonsillitis

Streptococcal culture or rapid test is the most important investigation. Clinical assessment is not accurate in determining the microbial aetiology.

Culture of a throat swab is the most accurate and least expensive method, provided that notification of the result to the patient and delivery of the prescription to the pharmacy are organized effectively.

Streptococcal culture also reveals non-A streptococci (no inhibition of haemolysis around a bacitracin disk).

If a rapid test is used, a negative result should be confirmed by culture (confirmation of a negative test is not necessary in children under the age of 3 years, as streptococcal disease is uncommon in this age group).

Finnish Medical Society Finnish Medical Society Duodecim (FMSD)Duodecim (FMSD). Sore . Sore throat and tonsillitis. In: EBM throat and tonsillitis. In: EBM Guidelines. Evidence-Based Guidelines. Evidence-Based Medicine [Internet]. Helsinki, Medicine [Internet]. Helsinki, Finland: Duodecim Medical Finland: Duodecim Medical Publications Ltd.; 2007 Feb 2. Publications Ltd.; 2007 Feb 2. [Various].[Various].

Diagnosis and treatment of respiratory illness in children

and adults. An appropriately performed

throat swab touches both tonsillar pillars and the posterior pharyngeal wall. The tongue should not be included (although its avoidance is sometimes technically impossible). Backup strep culture is needed if rapid strep test is negative. The best yield is obtained by using separate swabs for rapid strep test and strep culture. Backup systems such as polymerase chain reaction (PCR) may also be used.

Institute for Clinical Systems Improvement (ICSI). Diagnosis and treatment of respiratory illness in children and adults. Bloomington (MN): Institute for Clinical Systems Improvement (ICSI); 2008 Jan. 71 p. [175 references]

Rapid strep test has the following Rapid strep test has the following advantages:advantages: • • It has nearly 100% specificity.It has nearly 100% specificity. • • Rapid turnaround time reduces unnecessary Rapid turnaround time reduces unnecessary

short-term treatment while awaiting test results short-term treatment while awaiting test results and the associated complexity of interim treatment and the associated complexity of interim treatment strategies.strategies.

• • It potentially reduces need for callbacks.It potentially reduces need for callbacks. • • It allows the initiation of antibiotic in the timeliest It allows the initiation of antibiotic in the timeliest

fashion, reducing acute morbidity and contagion.fashion, reducing acute morbidity and contagion. • • Overall, rapid strep test may be more cost Overall, rapid strep test may be more cost

effective through reduced rework and reduced effective through reduced rework and reduced cycle time (Lieu, 1990 [M]).cycle time (Lieu, 1990 [M]).

• • Rapid strep test has high patient satisfaction, Rapid strep test has high patient satisfaction, even with associated wait time for results.even with associated wait time for results.

Rapid strep test has the following Rapid strep test has the following disadvantages or limitationsdisadvantages or limitations:: • • Lab costs are increased.Lab costs are increased. • • Current technology requires that negative rapid strep tests be Current technology requires that negative rapid strep tests be

backed up with strep culture because of relatively low sensitivities. backed up with strep culture because of relatively low sensitivities. Recent reports of new technology for optical immunoassay (OIA) are Recent reports of new technology for optical immunoassay (OIA) are encouraging for ultimately being able to use rapid strep test without encouraging for ultimately being able to use rapid strep test without culture backup. However, to date, results of studies on optical culture backup. However, to date, results of studies on optical immunoassay are limited and conflicting. Until more data is available, immunoassay are limited and conflicting. Until more data is available, it is recommended that all negative rapid strep tests be backed up it is recommended that all negative rapid strep tests be backed up with strep culture (Gerber, 1997 [C]; Schlager, 1996 [C]).with strep culture (Gerber, 1997 [C]; Schlager, 1996 [C]).

• • Recent study indicates the utility of a real-time polymerase chain Recent study indicates the utility of a real-time polymerase chain reaction assay as a replacement for both rapid antigen testing and reaction assay as a replacement for both rapid antigen testing and culture (Uhl, 2003 [C]). The polymerase chain reaction method culture (Uhl, 2003 [C]). The polymerase chain reaction method requires a minimum of 30 to 60 minutes to perform the test, and in requires a minimum of 30 to 60 minutes to perform the test, and in order to be used efficiently, it would require batch testing. It is order to be used efficiently, it would require batch testing. It is unlikely that this polymerase chain reaction method would be used as unlikely that this polymerase chain reaction method would be used as a waiting/rapid test.a waiting/rapid test.

• • Clinics may need to arrange new patient flow in the office and need Clinics may need to arrange new patient flow in the office and need to determine who will perform rapid strep test.to determine who will perform rapid strep test.

• • False positives may occur with retesting for up to 14 days following False positives may occur with retesting for up to 14 days following antibiotic course completion (presumably due to incomplete clearing antibiotic course completion (presumably due to incomplete clearing of strep antigen fragments that are still detected after clinical of strep antigen fragments that are still detected after clinical recovery).recovery).

• • It does not differentiate between illness and carrier states.It does not differentiate between illness and carrier states.

PharyngitisPharyngitis Laboratory confirmation: Test when

diagnosis is not ruled out by viral symptoms (see table below).

For adults: confirmation is most useful when GABHS is suspected; however, only test those with at least 2 or more signs/ symptoms mentioned above. [C].

For patients between 3 to 15 years of age: confirmation is most useful when GABHS cannot be excluded. Nevertheless, only test those with at least 1 or more signs/symptoms mentioned above [C]. The threshold for testing is lower for children because their risk of developing acute rheumatic fever is higher.

University of Michigan Health System. Pharyngitis. Ann Arbor (MI): University of Michigan Health System; 2006 Oct. 10 p. [9 references]

Throat culture is the presumed "gold standard" for diagnosis [C]. Rapid streptococcal antigen tests identify GABHS more rapidly, but have variable sensitivity [C].

Reserve rapid strep tests for patients with a reasonable probability of having GABHS. In patients screened with a rapid strep test, a negative result should be confirmed by culture in patients <16 years old (and considered in parents or siblings of school age children) due to their higher incidence of developing acute rheumatic fever [C].

If screening for GABHS in very low risk patients is desired, culture alone is cost effective.

University of Michigan Health System. Pharyngitis. Ann Arbor (MI): University of Michigan Health System; 2006 Oct. 10 p. [9 references]

PharyngitisPharyngitis

SIGNSIGN

DIAGNOSIS OF SORE THROAT

(B) Clinical examination should not be relied upon to differentiate between viral and bacterial sore throat.

(B )Throat swabs should not be carried out routinely in sore throat.

(B) Rapid antigen testing should not be carried out routinely in sore throat.Published January 1999.  Due for review 2007/8, Published January 1999.  Due for review 2007/8,

but publisher has confirmed the guideline's but publisher has confirmed the guideline's continued validity (November 2007).continued validity (November 2007).

Recommendation 1: Throat swab for culture: when and how

A throat swab should be taken when a diagnosis of strep throat is suspected from the clinical and epidemiological findings and the patient is not already taking antibiotics.

Technique: Using a sterile throat swab, contact the posterior pharyngeal wall and the surface of both tonsils, then place in an appropriate transport medium for prompt delivery to the laboratory.

A culture is usually the only test required. However, antibiotic sensitivity should also be requested in penicillin allergic patients due to the emergence of erythromycin resistant strains of streptococcus.

A culture is not indicated following a course of antibiotics for strep throat unless symptoms persist. Asymptomatic contacts of a patient with strep throat do not require cultures or empiric antibiotics

Revised Date: April 1, 2007

Rapid strep (antigen detection) tests lack sensitivity, lack evidence of improved clinical outcome and are NOT recommended.

DARE, DARE, NHS Economic Evaluations NHS Economic Evaluations DatabaseDatabase y HTA y HTA

Cost-effectiveness of treatment options for prevention of rheumatic heart disease from group A streptococcal pharyngitis in a pediatric populationEhrlich J E, Preventive Medicine 2002

Economic evaluation

The authors concluded "the most cost effective method of reducing the incidence of RHD (rheumatic heart disease) in a paediatric population presenting with pharyngitis potentially caused by a GAS (group A streptococcal) infection is the rapid antigen test with concomitant antibiotic treatment without the use of any confirmatory culture".

Are follow-up throat cultures necessary when rapid antigen detection tests are negative for Group A streptococci?Mayes T, Clinical Pediatrics 2001

Economic evaluation

Culture confirmation of rapid antigen detection (RAD) test-negative results may be unnecessary in children with pharyngitis, due to the low rate of false-negative results when all patients are tested. The economic analysis showed that substantial cost-savings may be realised from eliminating follow-up throat cultures, as a confirmation of negative RAD test results, from the point of view of the private practice and the patient. The cost of complications for undetected infections was fairly low.

Management of acute pharyngitis in adults: reliability of streptococcal test and clinical findingsHumair J P, Annals of Internal Medicine 2003

Economic evaluation

Authors' conclusions: Selective use of a rapid streptococcal antigen test (RSAT) in patients with at least 2 clinical findings suggestive of Group A streptococcal pharyngitis (GASP) is a cost-effective strategy to reduce the overuse of antibiotics and to appropriately treat acute pharyngitis in adults in a primary care setting.

Diagnosis and management of pharyngitis in a pediatric population based on cost-effectiveness and projected health outcomesVan Howe R S, Pediatrics 2006

Economic evaluation

From a health care payer perspective, the "no testing and no treatment" strategy resulted in the lowest morbidity and lower costs. The rapid antigen testing approach had the best cost-utility ratio. From a societal perspective, observing patients with pharyngitis resulted in the lowest morbidity rate while the approach of testing all patients using throat culture demonstrated a better cost-utility ratio.

Diagnosis and management of adults with pharyngitis: a cost effectiveness analysisNeuner J M, Annals of Internal Medicine 2003

Economic evaluation

Observation, culture, and two rapid antigen test strategies for the diagnostic testing and treatment of suspected beta-haemolytic streptococcus (GAS) pharyngitis in adults had very similar effectiveness and costs, although culture was the least expensive and most effective strategy when the GAS pharyngitis prevalence was 10%.

Otras fuentes…Otras fuentes…

Throat swabs have a limited place in routine use because they cannot distinguish between GABHS infection and carriage, and the delay in obtaining results limits clinical utility. In the UK, rapid antigen tests are also not currently recommended for routine use because of their limited specificity and sensitivity (their ability to rule in people with GABHS and to rule out people without the infection, respectively).

Dec 2006Dec 2006

Practice GuidelinesPractice GuidelinesDiagnosis and Management of Group A Diagnosis and Management of Group A Streptococcal Pharyngitis Streptococcal Pharyngitis Barrett M. SchroederBarrett M. Schroeder

The Infectious Diseases Society of America (IDSA) recently updated a 1997 The Infectious Diseases Society of America (IDSA) recently updated a 1997 guideline for the diagnosis and management of group A streptococcal pharyngitis. guideline for the diagnosis and management of group A streptococcal pharyngitis. The revised guideline was published in the July 15, 2002 issue of Clinical InfectiousThe revised guideline was published in the July 15, 2002 issue of Clinical Infectious

The IDSA recommends that, if acute group A The IDSA recommends that, if acute group A streptococcal pharyngitis is suspected, laboratory testing streptococcal pharyngitis is suspected, laboratory testing should be performed to support the diagnosis. Throat should be performed to support the diagnosis. Throat culture or a rapid antigen detection test (RADT) may be culture or a rapid antigen detection test (RADT) may be used. used. Culture of a throat swab specimen remains the standard Culture of a throat swab specimen remains the standard for identifying group A beta-hemolytic streptococci for identifying group A beta-hemolytic streptococci (sensitivity: 90 to 95 percent) and confirming the clinical (sensitivity: 90 to 95 percent) and confirming the clinical diagnosis. However, culture results are not available for a diagnosis. However, culture results are not available for a day or longer. RADTs identify group A streptococcal day or longer. RADTs identify group A streptococcal carbohydrate on a throat swab. Compared with blood agar carbohydrate on a throat swab. Compared with blood agar plate culture, most currently available RADTs have plate culture, most currently available RADTs have excellent specificity (greater than 90 percent) but lower excellent specificity (greater than 90 percent) but lower sensitivity (80 to 90 percent or less). For some RADTs, the sensitivity (80 to 90 percent or less). For some RADTs, the Clinical Laboratory Improvement Act has not waived the Clinical Laboratory Improvement Act has not waived the need for laboratory certification. need for laboratory certification.

Practice GuidelinesPractice GuidelinesDiagnosis and Management of Group A Diagnosis and Management of Group A Streptococcal Pharyngitis Streptococcal Pharyngitis Barrett M. SchroederBarrett M. Schroeder The IDSA notes that a positive result on a throat culture The IDSA notes that a positive result on a throat culture

or RADT adequately confirms the diagnosis. Unless the or RADT adequately confirms the diagnosis. Unless the physician has determined that the RADT used is physician has determined that the RADT used is comparable to throat culture, negative RADT results in comparable to throat culture, negative RADT results in children and adolescents should be confirmed with a children and adolescents should be confirmed with a throat culture. In adults, RADTs are an acceptable throat culture. In adults, RADTs are an acceptable alternative to throat culture for the diagnosis of group A alternative to throat culture for the diagnosis of group A streptococcal pharyngitis. Because of the low incidence streptococcal pharyngitis. Because of the low incidence of streptococcal infection in adults and the extremely of streptococcal infection in adults and the extremely low risk of rheumatic fever, negative RADT results do low risk of rheumatic fever, negative RADT results do not have to be confirmed by culture in adult patients. not have to be confirmed by culture in adult patients.

Except in patients with a history of rheumatic fever, Except in patients with a history of rheumatic fever, follow-up culture is not routinely indicated if a course of follow-up culture is not routinely indicated if a course of appropriate antibiotic therapy has been completed and appropriate antibiotic therapy has been completed and symptoms are absent. Follow-up culture should be symptoms are absent. Follow-up culture should be considered during outbreaks of acute rheumatic fever considered during outbreaks of acute rheumatic fever or poststreptococcal acute glomerulonephritis, during or poststreptococcal acute glomerulonephritis, during outbreaks of group A streptococcal pharyngitis in closed outbreaks of group A streptococcal pharyngitis in closed or partially closed communities, or when "ping-pong" or partially closed communities, or when "ping-pong" spread has been occurring within a family.spread has been occurring within a family.

P – nuestro paciente con P – nuestro paciente con faringoamigdalitisfaringoamigdalitis

I – uso del streptotestI – uso del streptotest C – frente al cultivo faringeo / clinicaC – frente al cultivo faringeo / clinica O – ayuda a tomar decisiones clinicas?O – ayuda a tomar decisiones clinicas?

90 pacientes cultivo pos (sensibilidad)90 pacientes cultivo pos (sensibilidad)

280 pacientes cultivo neg (especificidad)280 pacientes cultivo neg (especificidad)

Gracias !!!Gracias !!!