Table 3.

Linear regression results: association of diversity with age and antibiotic prophylaxis

Variable	β Coefficient	95% Confidence Interval		P Value
For OP diversity
Prophylactic antibiotics	−0.521	−0.979	−0.064	0.03
Age (months) at bronchoscopy	0.222	0.093	0.352	<0.01
Bacterial load, copies per ml	2.52E−10	1.76E−12	5.02E−10	0.049
For BAL diversity
Prophylactic antibiotics	−0.865	−1.264	−0.466	<0.01
Age at bronchoscopy, mo	0.229	0.114	0.343	<0.01

Beta coefficients from linear regression analysis for association of bacterial diversity in bronchoalveolar lavage (BAL) and oropharyngeal (OP) samples (analyzed separately) with use of prophylactic antibiotics and age (in months) at time of bronchoscopy. Lower diversity was associated with younger age and prophylactic antibiotics use. Bacterial load was associated with diversity in the model in oropharyngeal but not lavage samples. Other variables that were not significantly associated with bacterial diversity (and thus removed from the model by backward stepwise regression) included continent, interleukin-8 concentration, absolute neutrophil count, and volume pelleted (for lavage analysis only).