Does this coughing adolescent or adult patient have pertussis?

CONTEXT Pertussis is often overlooked as a cause of chronic cough, especially in adolescents and adults. Several symptoms are classically thought to be suggestive of pertussis, but the diagnostic value of each of them is uncertain. OBJECTIVE To systematically review the evidence regarding the diagnostic value of 3 classically described symptoms of pertussis: paroxysmal cough, posttussive emesis, and inspiratory whoop. DATA SOURCES, STUDY SELECTION, AND DATA EXTRACTION We searched MEDLINE (January 1966-April 2010), EMBASE (January 1969 to April 2010), and the bibliographies of pertinent articles to identify relevant English-language studies. Articles were selected that included children older than 5 years, adolescents, or adults and confirmed the diagnosis of pertussis among patients with cough illness (of any duration) with an a priori-defined accepted reference standard. Two authors independently extracted data from articles that met selection criteria and resolved any discrepancies by consensus. DATA SYNTHESIS Five prospective studies met inclusion criteria; 3 were used in the analysis. Presence of posttussive emesis (summary likelihood ratio [LR], 1.8; 95% confidence interval [CI], 1.4-2.2) or inspiratory whoop (summary LR, 1.9; 95% CI, 1.4-2.6) increases the likelihood of pertussis. Absence of paroxysmal cough (summary LR, 0.52; 95% CI, 0.27-1.0) or posttussive emesis (summary LR, 0.58; 95% CI, 0.44-0.77) reduced the likelihood. Absence of inspiratory whoop was less useful (summary LR, 0.78; 95% CI, 0.66-0.93). No studies evaluated combinations of findings. CONCLUSIONS In a nonoutbreak setting, data to determine the diagnostic usefulness of symptoms classically associated with pertussis are limited and of relatively weak quality. The presence or absence of posttussive emesis or inspiratory whoop modestly change the likelihood of pertussis; therefore, clinicians must use their overall clinical impression to decide about additional testing or empirical treatment.