Use of the intramuscular relative-dose-response test to predict bronchopulmonary dysplasia in premature infants

We tested the hypothesis that an intramuscular relative dose response (IM-RDR) on day 1 of Life would more accurately predict which premature infants would develop bronchopulmonary dysplasia (BPD) than single measurements of retinol, retinyl palmitate (RP), or retinol binding protein (RBP). Seventy-five premature infants less than or equal to 32 wk gestation had the IM-RDR on day 1 of life. An RDR greater than or equal to 25% occurred in 6 of 37 infants who did not develop BPD compared with 15 of 38 infants who developed BPD (P = 0.025). Retinol, RP, and REP on day 1 were not different between the groups. BPD infants who received postnatal dexamethasone during their hospital course had a higher day-28 baseline retinol concentration (1.19 +/- 0.15 mu mol/L) than did the group with no BPD (0.82 +/- 0.06 mu mol/L) (P = 0.03). However, the effect of postnatal dexamethasone on serum retinol was biphasic, rising initially, and then declining after 8-12 d. RP values at time 0 and 5 h on day 28 were higher than day 1 values in both infants without BPD and infants with BPD who did not receive dexamethasone. Retrospective analysis also revealed a significant correlation between a day-1 RDR greater than or equal to 25% and the incidence of intraventricular hemorrhage in these premature infants. Because the IM-RDR is more helpful in predicting the development of BPD than single serum retinol and RP analyses, this test could be useful in determining which premature infants might benefit from supplemental vitamin A for BPD.