Objective To investigate correlations of dynamic changes in serum C-reactive protein (CRP), procalcitonin (PCT), and neutrophil-to-lymphocyte ratio (NLR) before and after symptomatic treatment with prognosis of neonates with neonatal respiratory distress syndrome (NRDS) of different etiologies.

Methods A total of 110 premature infants were selected as study subjects and divided into neonatal infection group (group A) and fetal intrauterine distress group (group B) based on different causes of NRDS. Additionally, 30 neonates with NRDS caused solely by prematurity were selected as control group. Serum CRP and PCT levels and NLR were compared among the three groups before and after treatment.

Results There were statistically significant differences in oxygen therapy duration, ventilation duration, the proportion of infants requiring re-intubation, hospital stay, and the number of apnea episodes among three groups (P < 0.006). Before treatment, there was no statistically significant difference in serum CRP levels between group A and group B (P>0.05). Serum CRP levels in group B were higher than those in the control group. Moreover, serum PCT levels was lower than the group A, and NLR in the group B were higher than those in the group A and the control group. CRP, PCT levels, and NLR in the group A were higher than those in the control group (P < 0.05 or P < 0.006). After treatment, serum CRP levels in all three groups decreased compared to before treatment. Serum PCT levels in the group A decreased compared to before treatment. NLR in both group A and group B decreased compared to before treatment, with statistically significant differences (P < 0.006). There were statistically significant differences in serum CRP and PCT levels between the group A and the control group after treatment (P < 0.006). After treatment, there was a statistically significant difference in serum CRP levels between the group B and the control group (P < 0.006), but no statistically significant differences in PCT levels and NLR (P>0.05). Compared with group A, there was a statistically significant difference in PCT levels in the group B (P < 0.006). Multivariate Logistic regression results showed that CRP, PCT, and NLR were independent influencing factors for the prognosis of infants in the group A. The receiver operating characteristic curve analysis results showed that the areas under the curve (AUC) after treatment for serum CRP, PCT, and NLR alone in predicting prognosis in the group A were 0.789, 0.738, and 0.758, respectively, and the AUC for combined prediction was 0.934. In the group B, the AUC for serum CRP, PCT, and NLR alone in predicting prognosis after treatment were 0.719, 0.772, and 0.768, respectively, and the AUC for combined prediction was 0.886. The sensitivity and specificity of combined prediction in both groups were higher than those of each indicator alone, and the predictive value of their combined detection for the prognosis of premature infants in group A was higher than that in the group B.

Conclusion There are differences in PCT levels and NLR before treatment among neonates with NRDS of different etiologies. After symptomatic treatment, CRP, PCT levels and NLR decrease in all three groups, indicating a good prognosis.