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Diagnosing Strep Throat: Are There Reliable Clues?



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Am Fam Physician. 2001 Jul 1;64(1):157-158.

The antibiotic treatment of streptococcal pharyngitis (strep throat) decreases symptom severity and risk of transmission, and reduces the occurrence of suppurative complications and rheumatic fever. Ebell and colleagues conducted a literature review to determine the accuracy of physical examination in diagnosing strep throat.

Strep throat occurs more often in children than in adults or infants. It is more common in fall and winter. Symptoms associated with strep throat typically include severe sore throat (usually of abrupt onset in older children and adults), moderately high fever, chills, malaise, headache, mild neck stiffness and some gastrointestinal symptoms. These latter characteristics may be present in only 35 to 50 percent of patients with strep throat. Examination of the throat may reveal erythema and edema of the pharynx and uvula, and diffuse erythema and hypertrophy of the posterior pharyngeal tissue. A pharyngeal exudate or soft palate petechiae may also be seen, and halitosis is common. The anterior cervical lymph nodes are often tender and enlarged early in the course of strep throat. A fine erythematous papular rash may be seen on the trunk and extremities, and may be especially prominent in the antecubital fossae (Pastia sign). A “strawberry tongue” may occur.

All nine studies included in the review had at least 300 participants, used throat culture as the gold standard for the diagnosis of strep throat and made available information about the history and physical examinations.

The variables that were best able to discriminate between patients with and patients without strep throat were the presence of pharyngeal or tonsillar exudate, fever, enlarged tonsils, lymphadenopathy and absence of cough. The presence of a tonsillar exudate had a likelihood ratio of 3.4; pharyngeal exudate had a likelihood ratio of 2.1. Known strep throat exposure within the past two weeks had a likelihood ratio of 1.9. However, ruling out disease in the absence of physical and historical findings was difficult.

A number of clinical prediction rules have been developed for diagnosing strep throat. The McIsaac Modification of the Centor Strep Score (see accompanying figure) has been validated in a population of both adults and children. The cited article discusses other clinical prediction tools and algorithms.

McIsaac Modification of the Centor Strep Score

FIGURE 1.

Data from a group of 167 children aged 3 years and 453 adults in Ontario, Canada. Baseline risk of strep is 17 percent in this population. (LR = likelihood ratio)

Adapted with permission from McIsaac WJ, Goel V, To T, Low DE. The validity of a sore throat score in family practice. CMAJ 2000;163:811–5.

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McIsaac Modification of the Centor Strep Score


FIGURE 1.

Data from a group of 167 children aged 3 years and 453 adults in Ontario, Canada. Baseline risk of strep is 17 percent in this population. (LR = likelihood ratio)

Adapted with permission from McIsaac WJ, Goel V, To T, Low DE. The validity of a sore throat score in family practice. CMAJ 2000;163:811–5.

McIsaac Modification of the Centor Strep Score


FIGURE 1.

Data from a group of 167 children aged 3 years and 453 adults in Ontario, Canada. Baseline risk of strep is 17 percent in this population. (LR = likelihood ratio)

Adapted with permission from McIsaac WJ, Goel V, To T, Low DE. The validity of a sore throat score in family practice. CMAJ 2000;163:811–5.

The authors conclude that confirmation of the diagnosis of strep throat cannot be confirmed by a single history element or physical finding. Fever, tonsillar exudate, enlarged anterior cervical lymph nodes and absence of cough should be taken into account, along with the patient's age and the pretest probability of strep throat.

Ebell MH, et al. Does this patient have strep throat? JAMA. December 13, 2000;284:2912–8.



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