Pertussis predictors in hospitalized infants with acute lower respiratory tract infection

Background: Pertussis, or whooping cough, caused by Bordetella pertussis (BP) is a re-emerging problem in our environment. Although generally considered that the disease is relatively easy to identify infections respiratory syncytial virus (RSV) can present with similar symptoms in infants remains difficult discrimination.

Objective: Compare clinical symptoms at admission and complementary studies in infants hospitalized with acute respiratory infection (ARI) and RSV by BP to establish markers that enable their early clinical prediction.

Methods: Observational, analytical, case-crossover cross comparing younger than 6 months hospitalized with suspected IRA and pertussis (2007-2012) in which BP identified (PCR and culture) and / or VRS (immunofluorescence in nasal secretions). Coinfections were excluded. Bivariate analysis was performed by calculating OR with 95% CI. Were considered significant at p <0.05. The variables studied were age, sex, hits cough, cyanosis, vomiting, apnea, wheezing and CBC with differential

Results: We included 174 infants, 72 (41%) BP and 102 (59%) VRS. Age 2 ± 1 months (range :1-6). In both groups was documented cough and wheeze (OR: 1.2 (0.9 to 1.5) p: 0.1 and OR = 0.9 (0.8 to 1.06) p: 0.2, respectively ). Cyanosis (87% vs. 6%, OR: 14.8 p <0.01), apnea (38% vs. 3%, OR: 13.4 p <0.01) and vomiting (26% vs. 5% , OR: 3.4 p <0.01) were more frequent in infants with BP. The absolute lymphocyte count was significantly higher in children with BP (9387 ± 6317 vs. 5127 ± 2766, p <0.01). By ROC curve was identified at 9000 cells / ml as the best point to differentiate VSR BP (AUC = 0.73, 95% CI :0,64-0, 81).

Conclusions: In infants under 6 months with IRA income presence of apnea, cyanosis and lymphocytosis allowing predict significantly differentiate between pertussis those with RSV infections.