UTILITY OF RAPID ANTIGEN DETECTION TEST FOR GROUP A STREPTOCOCCI IN A FAMILY PAEDIATRICIAN OFFICE SETTING

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1 Acta Medica Mediterranea, 2010, 26: 101 UTILITY OF RAPID ANTIGEN DETECTION TEST FOR GROUP A STREPTOCOCCI IN A FAMILY PAEDIATRICIAN OFFICE SETTING ALESSANDRA MESSINA, *GAETANO BOTTARO, **IGNAZIO MORSELLI Medical Doctor - *Family Paediatrician, Gravina di Catania - Professor of Community and Family Medicine, Catania University - **Medico-Chirurgo [Utilità del test rapido per lo streptococco β-emolitico di gruppo A nell ambulatorio del pediatra di famiglia] SUMMARY Objectives. Acute pharyngotonsillitis (APT) is the most common child disease, that Family Paediatricians (FP) have to deal with. The aim of this study is to analyze validity of Rapid Antigen Detection Test (RADT), versus clinical scores to diagnose Group A Streptococci ST. Casistic. A three-years epidemiological investigation was performed on a group of children observed in a FP office. Children was divided into two groups on the basis of the RADT (RADT+ and RADT-) and for each group statistical and epidemiological analysis was performed. Results. A total of 1445 children was gathered, 1128 of them (78%) had RADT- and 317 (22%) RADT+. Data analysis shows significant statistical differences between data of children with RADT+, comparing to those of RADT-, regarding Milano Score and other clinical criteria, with the only exception of Mc Isaac Score. Conclusions. ST remains the most important children disease in an FP office. The use of RADT allows a rapids and correct etiological diagnosis and to contain to less than 50% antibiotic prescription. RADT is the diagnostic test to use in the FP practice, being easy and quick to perform, compared with clinical criteria and scores. Key words: Acute pharyngotonsillitis (APT), group A streptococci, rapid antigen detection test RIASSUNTO Obiettivi. La faringotonsillite (FT) rappresenta uno dei più frequenti problemi clinici del bambino ed è la patologia che più impegna il pediatra di famiglia (PdF). Scopo di questo studio è analizzare, dal punto di vista del PdF, la validità diagnostica del Test Rapido (TR) in confronto ai criteri clinici. Casistica. E stata effettuata un indagine epidemiologica su un largo campione di bambini visitati presso l ambulatorio di un PdF nel corso di un triennio. I bambini sono stati suddivisi in due gruppi, sulla base del risultato del TR (TR+ e TR-) e su ciascuno dei due gruppi sono state fatte le analisi epidemiologiche e statistiche. Risultati. Sono stati raccolti i dati clinici di 1445 bambini di cui 1128 a TR- (78%) e 317 a TR- (22%). L analisi dei dati ha dimostrato che esistono delle significative differenze tra i bambini a TR+ e quelli a TR-. Lo score Milano ha mostrato avere una attendibilità superiore rispetto al Mc Isaac nel distinguere le FT SBEGA dalle altre forme, anche se non si può affidare al dato clinico la diagnosi differenziale. Conclusioni. La FT rimane la patologia più importante per un PdF, l uso del TR ha consentito una discreta affidabilità diagnostica, consentendo di contenere a meno del 50% la prescrizione antibiotica ed in considerazione della facilità e rapidità di impiego, il TR è il test diagnostico, per le FT da utilizzare in ambulatorio, al contrario degli score e dei criteri clinici. Parole chiave: Faringotonsillite, streptococco di gruppo A, test rapido per la rivelazione dell antigene Introduction Acute pharyngotonsillitis (APT) represents one of the more frequent clinical complaint of the children that causes a lot of paediatric visits every year (1). Besides, as demonstrated by a report from family paediatrician (FP) activity, APT is the illness for which family paediatrician is frequently consulted in his daily work (2). Viruses are the most common cause of APT responsible over than 70%; Group A β-hemolityc Streptococcus (GAS) or Streptococcus pyogenes is the most important bacterium accounts for about 15 to 30% of all APT (3). It determines a strong infection that had a great important role in the paediatric pathology for the relevant complications such as rheumatic fever and acute glomerulonephritis. APT diagnosis is essential clinic, easy to do when a child, aged from 3 to 12, presents abrupt onset of fever, red throat with exudative tonsillitis, throat pain. More difficult is the etiological diagnosis. The rationale for accurate diagnosis and the main challenge is to distinguish between viral and GAS infection for the treatment strategy.

2 102 A. Messina, G. Bottaro et Al During the years, various clinical criteria are proposed in order to distinguish GAS APT (4-5). These clinical criteria are proposed alone or associated between them to compose an evaluation system (score). Two are the most used clinical scores Breese and McIsaac and among them Breese score has been widely used in Italy. However they demonstrated low sensitivity and specificity and Breese himself report a global predictivity of 77,8% (6). Diagnostic gold standard is throat culture with a sensibility of a 90-95% and specificity of 100% (7-8). There are many conditions, time firstly, that they can invalidate throat culture: above all the necessary time to having the outcome. Before hours it is impossible to obtain a result, therefore It is difficult for physicians to convince the parents of a cranky and febrile child of the wisdom of with holding antibiotics (9). Rapid antigen detection testing (RADT) has many benefits and is now widely available, but it is critical to whether a RADT is cost effective in the APT diagnosis if used as a stand-alone test without a selection patients (10-11). This selection can be performed using clinical scores or single clinical symptoms. FP is usually the first care provider that sick children meet within the Italian National Health Service. Aim of this study has been to evaluate the usefullness of RADT in the FP daily activity. Casistic We take into consideration in this series all the children admitted to the FP s office during the years who presented with complaint of acute pharyngotonsillitis. Moreover to all these children have been carried out a RADT for the determination of the antigen GAS and the eventual positive result has been considered synonymous of GAS presence. RADT used during the study period have been as follows: QuickVue + Strep A and Dipstick Strep A test, Quidel; lcon -Fx Strep A, Beckmam Coulter; Test Pack + Plus Abbott For every child we registered the followed data: diagnosis age, onset month, presence of fever (>38 C), sore throat, cough, tender and/or enlarged lymph nodes, headache, tonsillar exudates, palatine petechiae, recent history of APT (last six months). Clinical evaluation has been completed by calculating two clinical scores: Milano score (Breese s score without leukocytosis) (14) and Mc Isaac s score (15). For each data has been calculated: frequency, mean, standard deviation and statistical analysis using Student t test, analysis of variance and χ2. Results During the three years period a total of 1445 children with APT was gathered. 759 were female (53%) and 686 male (47%), mean age was 4.84±3.21 years, range 1 month 15 years and 8 months. 541 (38%) children were seen during 2007, 495 (34%) in 2008 and 408 (28%) in While 1128 (78%) children had negative RADT (RATD-), 317 (22%) were positive (RATD+). All these results are resumed in Table 1. Parameters Results % Total cases 1445 Mean age Range 4.84±3.21 years 1 month 15 years 8 months F/M ratio RADT RADT Table 1: General data of the study Group children RATD+ showed a mean age of 6.62±2,86 years, significantly higher (p<0,001) then those with RADT- 4.33±3.12 years, with a higher distribution in the 0-6 years age range for RADT-. On the contrary children with RADT+ showed an higher distribution in the 3-10 age range (Figure 1). High statistical significance (p<0.001) showed the average difference referred to the Milano Score between the two groups: children with RADT ±2,32, children with RADT ±2.10. On the contrary no statistical significance showed the average difference referred to the McIsaac s Score: children with RADT- 3.43±0.68, children with RADT+ 3.51±0.62. Milano Score data analysis showed that while 53% of the children with RADThad a score lower then 22, 67% of the children with RADT+ had score between 23 to 26; about all children of the two groups (96% of RADT- and 87% of

3 Utility of rapid antigen detection test for group A streptococci in a family paediatrician office setting 103 RADT+), had a score lower then 26 with a total overlapping area (Figure 1). Monthly distribution showed a similar trend for both groups with high incidence during spring and autumn and low frequency during summer and winter. Regarding the use of the antibiotic: 571 children (51% of the children) RADT- have not received some antibiotic, while 557 (49%) have received it and of these 45 (8%) have received penicillin, 502 (90%) a cephalosporin and 10 (2%) a macrolide. In the group of the children with RADT+ all 317 children (100%) have received an antibiotic and of these 31 (10%) have received penicillin, 285 (90%) a cephalosporin and only 1 child macrolide (Table 2). Discussion Fig 1: Distribution of Milano Score Frequency analysis of the onset symptoms showed that 58% of the children with RADT- and 53% of the children with RADT+ had fever >38 C; 13% of RADT- children and 38% of RADT+ children had sore throat (χ2 p<0,001); 15% of RADTchildren and 8% of RADT+ children had cough (χ2 p<0,001); 2% of RADT- children and 6% of RADT+ children had tender lymph nodes (χ2 p<0,001); 1% of RADT- children and 3% of RADT+ children had headache; 16% of RADTchildren and 54% of RADT+ children had tonsillar exudate (χ2 p<0,001); l 1% of RADT- children and 4% of RADT+ children had palatine petechiae (χ2 p<0,001); 33% of RADT- children and 14% of RADT+ children suffered from one or more APT episode, in the former months (χ2 p<0,001). APT RADT - APT RADT + n. % n. % No antibiotic Antibiotic Penicillin Cephalosporin Macrolide Table 2: Antibiotic Use Fig 2: Age distribution of the cases This clinical report confirms many typical APT characteristics. Firstly APT is one of the most important diseases for FP occurring for the 20% of the total daily visits, about 500 cases per year (12). In our series 22% of the APT total is RADT+ and then closely related to GAS (13) (Table 1). Data analysis of clinical symptoms (Table 3) showed some differences between the two series. About mean age, while children with RADT+ are concentrated over 15 months of life and in the 3-10 years age range (85%), children with RADT- presented high frequency within 6 years of age particularly under 3 years old (Figure 2). As regard clinical score and analysis of symptoms, they need a careful consideration. Data analysis showed that, McIsaac s Score do not have any difference between two groups, on the contrary Milano Score had a important and statistical significance difference. In fact statistical analysis between the two average using Student t test and χ2 used to compare score frequencies showed in both cases high statistical significance. It is possible to note that while most children with RADT- had score <22, most children with RADT+ had score between

4 104 A. Messina, G. Bottaro et Al 23 and 26. However, in both groups, almost every children had a score lower than 26 and plotting a graphic with overlapped areas it is clearly evident the perfect correspondence and the overlap of the two curves (Figure 2). This behavior demonstrates that on a single case it is difficult to discriminate. Then we conclude that: McIsaac s score is not useful in childhood APT; children lower than 18 months of age had the certainty of GAS absence; children with Milano Score lower than 22 are quite sure do not have GAS APT and on the contrary children with Milano Score upper than 27 are quite sure to have GAS APT. Parameters RADT - RADT + n. % n. % Total cases Mean age 4.33±3.12 years 6.62±2.86 years* Range 1 month 15 years 8 months 15 months 14 years 9 months Milano Score 22.38± ±2.10* < In this series of cases we prefer to use for APT an etiological diagnostic approach, using RADT, based on polysaccharide membrane GAS antigen extraction. It is now accepted that a RADT positivity demonstrate GAS presence, on the contrary RADT negativity need, as reported by AAP, culture confirmation to demonstrate GAS presence (13). Throat culture, in current practices involves the problem of the time occurring to have a result Within hours it is impossible to have a result and it is difficult for physicians to convince the parents of a cranky and febrile child of the wisdom of withholding antibiotics (9). This behaviour explains because a lot of visits for APT are concluded with an antibiotic prescription (1-16). In this study the use of the RADT has not only allowed to less contain of 50% the antibiotic prescription in negativity case, but also it has allowed to identify the patients correctly with suspects GAS presence and to begin with timeliness the therapy. Today for its characteristics, easiness and quickness RADT use as diagnostic test for APT is mandatory in pediatric daily current practice > McIsaac s Score 3.43± ±0.62** Fever >38 C Sore throat Cough Tender lymph nodes Headache Tonsillar exudate Palatine petechiae History of APT * Student t test p<0.001 ** no significant Student t test χ2 p<0.001 no significant χ2 Table 3: Analysis of the clinical data in the two groups References 1) Schwartz B, Fries S, Fitzgibbon AM, Lpman H: Pediatricians diagnostic approach to pharyngitis and impact of CLIA 1988 on office diagnostic tests. Jama 1994; 271: ) Bottaro G, Bucchieri R, De Luca P, Ficarra G, Gulino A, Miano G, Patanè G, Raciti-Longo A, Rotolo N: Indagine sull attività ambulatoriale dei pediatri di base della provincia di Catania. Il Medico Pediatra ) Bisno AL: Acute pharyngitis. N Engl J Med 2001; 18: ) Breese BB, Disney FW: The accuracy of diagnosis of beta streptococcal infections on clinica grounds. J Pediatr 1954; 44: ) McIsaac WJ, Goel V, Tot, Low De: The validity of a sore throat score in family practice. CMAJ 2000; 163: ) Breese BB A simple scorecard for the tentative diagnosis of streptococcal pharyngitis. Am J Dis Child 1977; 131: ) Bisno AL: Acute pharyngitis: etiology and diagnosis. Pediatrics 1996;97(suppl): ) Bisno AL, Gerber MA, Gwaltney JM, Kaplan EL, Schwartz RH: Diagnosis and management of group A streptococcal pharyngitis: a practice guideline. Clin Infect Dis 1997; 25:

5 Utility of rapid antigen detection test for group A streptococci in a family paediatrician office setting 105 9) Roddey OF Jr, Clegg HW, Martin ES, Swetenburg RL, Koonce EW: Comparison of throat culture methods for the recovery of group A streptococci in a pediatric office setting. Jama 1995; 274: ) Gieseker KE, Mackenzie T, RoeE MH, Todd JK: Comparison of two rapid Streptococcus pyogenes diagnostic tests with a rigorous culture standard. Pediatr Infect Dis J. 2002; 21: ) Gieseker KE, Roe MH, Mackenzie T, Todd JK: Evaluating the American Academy of Pediatrics diagnostic standard for streptococcus pyogenes pharyngitis: backup culture versus repeat rapid antigen testing. Pediatrics 2003; 111: e666 -e ) Morselli I, Bottaro G: Report sull'attività ambulatoriale di un pediatra di famiglia: analisi del triennio Riv Ped Sicil in corso di stampa 13) American academy of pediatrics. Group A streptococcal infections. In: Pickering LK, ed. Red Book: 2003 Report of the Committee on Infectious Diseases. 26th ed.. Elk Groove Village, IL: American Academy of Pediatrics; 2003: ) Boccazzi A, Tonelli P, Ceruti R: What s new in streptococcal pharyngitis. Int J Antimicrob Agents 2000; 16: ) McIsaac WJ, White D, Tannenbaum D, Low DE: A clinical score to reduce unnecessary antibiotic use in patient with sore throat. CMAJ 1998; 158: Cucinotta G, Mazzaglia G, Toscano MA, Arcoraci V, Tempera G, Salmeri M, Rosignoli M, Bottaro G, Boccazzi A, Nicoletti G, Caputi AP: Exploring the variability in antibiotic prescribing profiles among paediatricians from two different areas of Italy. Pharmacol Res. 2002; 45: Request reprints from: Dott.ssa ALESSANDRA MESSINA Via Filippo Juvara, Siracusa (Italy)