Original Article
Validation and Modification of Streptococcal Pharyngitis Clinical Prediction Rules

https://doi.org/10.4065/78.3.289Get rights and content

Objective

To validate a simplified version of the Walsh clinical prediction rules (CPRs) for the presence of streptococcal pharyngitis in an inner-city, ethnically diverse population.

Patients and Methods

This prospective study conducted in New York City, NY, from January 1, 1997, to May 31, 1997, consisted of 171 consecutive adult walk-in patients who presented with symptoms of upper respiratory tract infection and/or sore throat. The patients were assessed by using 5 clinical factors: cough, exposure to known streptococcal contact, temperature, tonsillar-pharyngeal exudates, and cervical lymphadenopathy. Throat cultures for group A β-hemolytic streptococcus were obtained from all patients. Clinicians assessing the patients were unaware of throat culture results, and those processing the throat cultures were blinded to the clinical predictors.

Results

The prevalence of streptococcal pharyngitis was 24% (95% confidence interval, 18%-30%). The simplified version of the Walsh CPR for streptococcal pharyngitis predicted accurately the probability of a positive culture in our diverse population (area under the receiver operating characteristic curve, 0.71). The simplified CPR also showed clinically useful likelihood ratios and posterior probabilities.

Conclusion

A simplified version of the Walsh CPR is accurate for diagnosing streptococcal pharyngitis in an inner-city population. This finding should provide clinicians more confidence in applying the CPR in similar clinical settings.

Section snippets

PATIENTS AND METHODS

The study was conducted prospectively from January 1, 1997, to May 31, 1997, at the primary care clinic of an inner-city hospital in New York City, NY. We enrolled 171 consecutive unscheduled adult walk-in patients who presented with symptoms of upper respiratory tract infection and/or sore throat. Patients were first triaged by staff nurses and then seen by residents or attending physicians. All patients were assessed with use of the 5 predictors in the CPRs (Table 1, Table 2). The predictors

RESULTS

Of the 171 enrolled patients, 5 were excluded because the results of throat cultures were not available. The preva lence of streptococcal pharyngitis in our population was 24% (95% confidence interval [CI], 18%-30%). The mean age was 35 years (range, 18-74 years), and 23% of the patients were men (Table 3).

Both the original Walsh CPR and the simplified version predicted accurately the probability of a positive culture for GABHS. The ROC curves (Figure 1) and areas under the ROC curves of the

DISCUSSION

Because of the large number of published CPRs, it appears that physicians have become aware of and have incorporated the important clinical predictors for streptococcal pharyngitis into their day-to-day management of patients. However, physicians have simplified the process, assessing probability of GABHS infection by counting the number of variables present in a patient. If no clinical predictors are present (score, -1), no treatment is offered; if several predictors are present (score, ≥2),

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Cited by (0)

This study was funded and supported in part by the Department of Internal Medicine, Albert Einstein College of Medicine, Montefiore Medical Center, New York, NY.

Presented in part at the Society of General Internal Medicine National Convention, Chicago, Ill, April 30, 1998.

Individual reprints of this article are not available.

1

Dr Ahlawat is now with Georgetown University Hospital, Washington, DC

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