Diagnostic accuracy of oropharyngeal cultures in infants and young children with cystic fibrosis

The objective of this study was to assess the diagnostic accuracy of oropha ryngeal (OP) cultures relative to simultaneous bronchoalveolar lavage (BAL) cultures in very young children with CF, and to examine the effects of bac terial density, age, and study cohort on diagnostic accuracy. Respiratory c ulture data were analyzed from three independent, prospective studies invol ving simultaneous collection of 286 OP and BAL cultures from 141 children w ith CF <5 years of age. For predicting any growth of Pseudomonas aeruginosa (Pa) from the lower air way in subjects less than or equal to 18 months of age (mean age, 8 +/- 5 m onths), OP cultures had a sensitivity of 44% (95% CI 14%, 79%), specificity of 95% (90%, 99%), positive predictive value of 44% (14%, 79%), and negati ve predictive value of 95% (90%, 99%). Diagnostic accuracy was similar for Haemophilus influenzae (Hi). Specificity was significantly lower for Staphy lococcus aureus (Sa). Sensitivity for all organisms improved if a positive lower airway culture was defined as greater than or equal to 10(3) or great er than or equal to 10(5) cfu/mL. Specificity for Pa declined significantly with increasing age. In children with CF <5 years of age, the specificity and negative predictiv e value of OP cultures for Pa are high, while the sensitivity and positive predictive value are poor. Thus, in this age range, a negative throat cultu re is helpful in "ruling out" lower airway infection with Pa. However, a po sitive culture does not reliably "rule in" the presence of Pa in the lower respiratory tract. These findings may have implications for study design an d interpretation as well as clinical management of young children with CF. Pediatr Pulmonol, 1999;28:321-328, (C) 1999 Wiley-Liss, Inc.