Diagnosing Strep Throat in the Adult Patient: Do Clinical Criteria Really Suffice?

Editorials15 July 2003Diagnosing Strep Throat in the Adult Patient: Do Clinical Criteria Really Suffice?FREEAlan L. Bisno, MDAlan L. Bisno, MDFrom University of Miami School of Medicine; Miami Veterans Affairs Medical Center; Miami, FL 33125.Author, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-139-2-200307150-00015 SectionsAboutVisual AbstractPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail Although pharyngitis caused by the group A -hemolytic streptococcus (GAS) is one of the most common human infections and has been studied intensively for decades, considerable debate remains about the most appropriate method of diagnosis and treatment. Most cases of acute pharyngitis seen in primary care practice are viral in cause; GAS is the only commonly occurring cause of sore throat for which antimicrobial therapy is indicated. Moreover, the signs and symptoms of GAS pharyngitis and viral pharyngitis overlap so broadly that precise diagnosis on clinical grounds is difficult. For this reason, practice guidelines issued by the American Heart Association (1), American Academy of Pediatrics (2), and Infectious Diseases Society of America (3) advocate microbiological confirmation of the diagnosis by throat culture or a rapid antigen diagnostic test. Because the latter is generally less sensitive than throat culture, these guidelines suggest that a negative result be backed up by throat culture. The necessity for this has been questioned, however (4), especially because supposedly more sensitive rapid tests, such as optical immunoassay (OIA), have appeared on the market (5).Several clinical algorithms help clinicians assess the probability that a given adult patient with acute pharyngitis has GAS infection (6, 7). Recently, a practice guideline of the American College of Physicians (ACP) recommended that one such algorithm may be used to diagnose GAS pharyngitis in adults on clinical grounds alone, eschewing microbiological testing. The Centers for Disease Control and Prevention and the American Academy of Family Physicians have also approved this recommendation.This algorithm, developed by Centor and associates (8), relates the probability of GAS pharyngitis to four clinical findings: tonsillar exudates, tender anterior cervical adenopathy, absence of cough, and history of fever. The ACP guideline was published in two papers (9, 10) that have slightly differing recommendations. The ACP guidelines allow for using a rapid antigen diagnostic test or, alternatively, empirically treating patients who meet three or four Centor criteria and nontreatment of all others. I think it is unlikely that clinicians will perform cultures or rapid tests when a practice guideline endorsed by so many prestigious organizations states that clinical criteria suffice.According to the National Ambulatory Care Survey, between 1989 and 1999 adults made an estimated 6.7 million visits to primary care office-based physicians with the chief symptom of sore throat (11). Thus, issues of appropriate diagnosis and treatment have major public health import. Minimizing unnecessary antimicrobial therapy in adults is highly desirable because the prevalence of GAS pharyngitis in this group is low (estimated to be in the 10% range) and the risk for the most feared sequela of this condition, acute rheumatic fever, is remote.In this issue, Neuner and colleagues (12) report a detailed cost-effectiveness analysis of the diagnosis and management of U.S. adults with pharyngitis. The authors extensively reviewed the pertinent literature and constructed a careful analysis using the best available evidence on the magnitude of the relevant variables. They compared five management strategies: no testing or treatment, empirical treatment with penicillin, throat culture using a two-plate selective technique, OIA backed up by culture if OIA results are negative, or OIA alone. They further examined the effect of the Centor clinical prediction rule on these strategies. Assuming a GAS prevalence of 10% in adults with pharyngitis, they found empirical treatment to be the least effective in terms of quality-adjusted life-days. Although all other strategies were similarly effective, culture was the most cost-effective. When these findings were subjected to sensitivity analysis, empirical treatment based on the Centor criteria was neither most effective nor least expensive at any GAS pharyngitis prevalence likely to be found in U.S. adult populations.The stated goal of the ACP guideline is dramatically decreasing excess antibiotic use (10). As a result, examining in further detail the consequences of the empirical therapy recommendation would be helpful. In Centor and colleagues' study, only 10% of adult patients (>15 years of age) presenting to an urban emergency department met all four criteria, and throat culture was positive in 56% of these patients. In the 20% of patients meeting three criteria, the probability of a positive culture was only 30% to 34%. Therefore, the combined positive predictive value associated with meeting three or four of the clinical criteria would be approximately 40%. This means that 60% of the patients treated empirically would have had a negative result on GAS culture or a rapid antigen diagnostic test (13, 14). Use of the Centor algorithm does indeed identify patients whose risk for GAS infection is so low that microbiological testing or antibiotic treatment is unnecessary.As pointed out by Neuner and colleagues (12), the risk for preventable severe suppurative or nonsuppurative infections in adults with GAS pharyngitis is small. Antimicrobial therapy may truncate the illness, but only if started early in the illness and only by a day or two. Such treatment may decrease spread of the infection to close contacts. Given this limited benefit, the main purpose of any diagnostic strategy for adults should be to minimize unnecessary antimicrobial therapy. This latter point is of particular importance in view of national data indicating that antibioticsfrequently the more expensive, broader-spectrum onesare prescribed for approximately three quarters of adults who consult community primary care physicians because of a sore throat (11). After considering these facts, the Infectious Diseases Society of America, in a revised practice guideline (3) not cited by Neuner and colleagues, now advocates use of the rapid antigen diagnostic test alone to confirm the diagnosis of GAS pharyngitis in adults. This strategy is simpler than throat culture and yields results that allow rapid treatment decisions. The generally high specificity of a rapid test should minimize overprescription of antibiotics for adults with acute pharyngitis. It is comforting to see that in Neuner and associates' analysis, the performance of a rapid diagnostic test without culture backup was similar to that of a strategy requiring culture confirmation of negative rapid test results.There are several caveats. First, a positive result on throat culture or rapid test only confirms GAS presence in the pharynx and does not in itself differentiate acute infection from chronic carriage. In everyday primary care practice, however, this should have a negligible effect because carriage rates in adults are low. Second, the prevalence of positive throat cultures may be higher than the usually quoted 5% to 10% in adults who have intensive exposure to children (such as mothers of school-aged children and schoolteachers); as a result, a higher index of suspicion, and perhaps backup of rapid antigen diagnostic testing with throat culture, might be warranted in such persons.Once a test result is positive, the American Heart Association, American Academy of Pediatrics, and Infectious Diseases Society of America recommend penicillin as the drug of choice for nonallergic patients. Particularly undesirable is the practice of prescribing the newer macrolide agents as first-line empirical therapy for febrile patients with upper respiratory tract infections (15). While penicillin-resistant group A -hemolytic streptococci have never been recovered from any clinical source (16), macrolide resistance develops rapidly in communities that use these drugs extensively (17). Fortunately, such resistance has to date been reported from only a few places in the United States (18, 19), but constant surveillance is necessary.The ultimate test of the most cost-effective and beneficial strategy for managing acute GAS pharyngitis would of course be a controlled clinical trial. Indeed, the authors of the ACP guidelines suggest that prospective studies should be conducted to determine relevant patient outcomes and costs (9). Unless and until such studies are performed, and for the reasons outlined above, I do not believe it is prudent to rely exclusively on clinical criteria for diagnosis and management of GAS pharyngitis.References1. Dajani A, Taubert K, Ferrieri P, Peter G, Shulman S. Treatment of acute streptococcal pharyngitis and prevention of rheumatic fever: a statement for health professionals. Committee on Rheumatic Fever, Endocarditis, and Kawasaki Disease of the Council on Cardiovascular Disease in the Young, the American Heart Association. Pediatrics. 1995;96:758-64. [PMID: 7567345] MedlineGoogle Scholar2. Committee on Infectious Diseases. Pickering LK, eds. Group A streptococcal infection.. In: Pickering LK, eds. 2000 Red Book. 25th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2001:526-36. Google Scholar3. Bisno AL, Gerber MA, Gwaltney JM, Kaplan EL, Schwartz RH. Practice guidelines for the diagnosis and management of group A streptococcal pharyngitis. Infectious Diseases Society of America. Clin Infect Dis. 2002;35:113-25. [PMID: 12087516] CrossrefMedlineGoogle Scholar4. Webb KH. Does culture confirmation of high-sensitivity rapid streptococcal tests make sense? A medical decision analysis. Pediatrics. 1998;101:E2. [PMID: 9445512] CrossrefMedlineGoogle Scholar5. Gerber MA, Tanz RR, Kabat W, Dennis E, Bell GL, Kaplan EL, . Optical immunoassay test for group A -hemolytic streptococcal pharyngitis. An office-based, multicenter investigation. JAMA. 1997;277:899-903. [PMID: 9062328] CrossrefMedlineGoogle Scholar6. Walsh BT, Bookheim WW, Johnson RC, Tompkins RK. Recognition of streptococcal pharyngitis in adults. Arch Intern Med. 1975;135:1493-7. [PMID: 1103766] CrossrefMedlineGoogle Scholar7. Komaroff AL, Pass TM, Aronson MD, Ervin CT, Cretin S, Winickoff RN, . The prediction of streptococcal pharyngitis in adults. J Gen Intern Med. 1986;1:1-7. [PMID: 3534166] CrossrefMedlineGoogle Scholar8. Centor RM, Witherspoon JM, Dalton HP, Brody CE, Link K. The diagnosis of strep throat in adults in the emergency room. Med Decis Making. 1981;1:239-46. [PMID: 6763125] CrossrefMedlineGoogle Scholar9. Cooper RJ, Hoffman JR, Bartlett JG, Besser RE, Gonzales R, Hickner JM, . Principles of appropriate antibiotic use for acute pharyngitis in adults: background. Ann Intern Med. 2001;134:509-17. [PMID: 11255530] LinkGoogle Scholar10. Snow V, Mottur-Pilson C, Cooper RJ, Hoffman JR. Principles of appropriate antibiotic use for acute pharyngitis in adults. Ann Intern Med. 2001;134:506-8. [PMID: 11255529] LinkGoogle Scholar11. Linder JA, Stafford RS. Antibiotic treatment of adults with sore throat by community primary care physicians: a national survey, 1989-1999. JAMA. 2001;286:1181-6. [PMID: 11559262] CrossrefMedlineGoogle Scholar12. Neuner JM, Hamel MB, Phillips RS, Bona K, Aronson MD. Diagnosis and management of adults with pharyngitis. A cost-effectiveness analysis. Ann Intern Med. 2003;139:113-22. LinkGoogle Scholar13. Bisno AL, Peter GS, Kaplan EL. Diagnosis of strep throat in adults: are clinical criteria really good enough? Clin Infect Dis. 2002;35:126-9. [PMID: 12087517] CrossrefMedlineGoogle Scholar14. Peter GS, Bisno AL. Group A streptococcal pharyngitis in adults: diagnosis and management. In: Pechere JC, Kaplan EL, eds. Streptococcal Pharyngitis. Basel, Switzerland: Karger; 2003 [In press]. Google Scholar15. Steinman MA, Landefeld CS, Gonzales R. Predictors of broad-spectrum antibiotic prescribing for acute respiratory tract infections in adult primary care. JAMA. 2003;289:719-25. [PMID: 12585950] CrossrefMedlineGoogle Scholar16. Horn DL, Zabriskie JB, Austrian R, Cleary PP, Ferretti JJ, Fischetti VA, . Why have group A streptococci remained susceptible to penicillin? Report on a symposium. Clin Infect Dis. 1998;26:1341-5. [PMID: 9636860] CrossrefMedlineGoogle Scholar17. Seppala H, Klaukka T, Vuopio-Varkila J, Muotiala A, Helenius H, Lager K, . The effect of changes in the consumption of macrolide antibiotics on erythromycin resistance in group A streptococci in Finland. Finnish Study Group for Antimicrobial Resistance. N Engl J Med. 1997;337:441-6. [PMID: 9250845] CrossrefMedlineGoogle Scholar18. Freeman AF, Shulman ST. Macrolide resistance in group A Streptococcus . Pediatr Infect Dis J. 2002;21:1158-60. [PMID: 12488669] CrossrefMedlineGoogle Scholar19. Martin JM, Green M, Barbadora KA, Wald ER. Erythromycin-resistant group A streptococci in schoolchildren in Pittsburgh. N Engl J Med. 2002;346:1200-6. [PMID: 11961148] CrossrefMedlineGoogle Scholar Comments0 CommentsSign In to Submit A Comment Author, Article, and Disclosure InformationAffiliations: From University of Miami School of Medicine; Miami Veterans Affairs Medical Center; Miami, FL 33125.Disclosures: Dr. Bisno was chair of the Infectious Diseases Society of America's committee on guidelines for GAS pharyngitis.Corresponding Author: Alan L. Bisno, MD, 1201 NW 16th Street, Miami, FL 33125. PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetailsSee AlsoDiagnosis and Management of Adults with Pharyngitis: A Cost-Effectiveness Analysis Joan M. Neuner , Mary Beth Hamel , Russell S. Phillips , Kira Bona , and Mark D. 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