UREAPLASMA-UREALYTICUM AND CHRONIC LUNG-DISEASE OF PREMATURITY - CRITICAL-APPRAISAL OF THE LITERATURE ON CAUSATION

A critical appraisal of four cohort studies examining the relationship between Ureaplasma urealyticum and chronic lung disease (CLD) of prem aturity is presented. Three studies were concurrently conducted, but t he fourth was conducted 4 years later when surfactant replacement was a widespread practice. Although infants were enrolled in all studies s oon after birth before. they had developed CLD, there were differences in patient population, the definition of colonization with U. urealyt icum, neonatal management, and the definition of CLD of prematurity. D espite the differences, all four studies found an association between colonization and development of CLD of prematurity. A combined estimat e of relative risk for the four studies was 1.91 (95% confidence inter val, 1.54-2.37). When infants were categorized into groups by birth we ight, the association was not observed in infants who weighed >1,250 g . The association was also not observed in infants who weighed <750 g, but the risk of CLD of prematurity in the uncolonized control group w as already 82%. Because the cohort study design allows for the possibi lity that one or more additional factors associated with U. urealyticu m may be the true cause(s) of CLD of prematurity, there is strong but not definitive evidence that U. urealyticum causes CLD of prematurity.