Concordance of Clinical Findings and Clinical Judgment in the Diagnosis of Streptococcal Pharyngitis

Authors

  • Haq Nawaz MD, MPH,

    Corresponding author
    1. Department of Preventive Medicine, Griffin Hospital, Derby, CT (HN, RM, DLK)
    2. Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT (HN, DLK).
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  • David S. Smith MD,

    1. Yale University Health Services, New Haven, CT (DSS)
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  • Ramesh Mazhari MD,

    1. Department of Preventive Medicine, Griffin Hospital, Derby, CT (HN, RM, DLK)
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  • David L. Katz MD, MPH

    1. Department of Preventive Medicine, Griffin Hospital, Derby, CT (HN, RM, DLK)
    2. Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT (HN, DLK).
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Yale—Griffin Prevention Research Center, Griffin Hospital, 130 Division Street, Derby, CT 06418. Fax: 203-732-1264; e-mail: haqnawaz@pol.net

Abstract

Abstract. Objective: It is uncertain how reliably clinicians apply clinical predictors of group A beta hemolytic streptococcal pharyngitis (GABHSP) to form a clinical impression, and how reliably this impression predicts culture results. The objective was to study clinician accuracy in diagnosing GABHSP. Methods: This was a prospective cohort study, conducted at an urgent care center of a major university. A convenience sample of 218 patients, aged 9-83 years, presenting with sore throat, was enrolled. Symptoms and signs of pharyngitis were documented on a standardized form; the likelihood of GABHSP was plotted on a visual analog scale; and throat culture was obtained. A comparison was then made between the clinical impression on presentation and the throat culture result. Results: Throat cultures were positive for GABHSP in 41 patients (19%). The probability of GABHSP was related to node size and tenderness, tonsillar exudate and hypertrophy, and pharyngeal erythema (p < 0.05); but not throat soreness, degree of fever, or cough. A strong clinical impression of GABHSP (>50% on the visual analog scale) was associated with tonsillar exudate and hypertrophy, tender nodes, and pharyngeal erythema. Together, these four predictors had a sensitivity of 71%, a specificity of 77%, and a positive predictive value of 46%. Conclusions: Clinicians in this study based their impression of GABHSP on the most reliable symptoms and signs. While a strong clinical suspicion of GABHSP predicted a greater probability of positive culture, the clinicians consistently overestimated the probability of GABHSP. Symptoms and signs predict GABHSP unreliably when used alone; they are helpful in modifying estimates of disease probability to facilitate optimal use of laboratory tests and antibiotics.

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