To the Editor: We thank the authors for reading our article [1] in great detail and bringing to our notice some important questions [2].

Even though SNAP-II was developed as a severity score at admission to NICU, previous studies have validated this score in other disease settings (sepsis, pulmonary hypertension) [3]. Such studies can be considered as validation studies testing the severity score in different settings and indications [4].

Death after enrolment was not an exclusion criterion. The serial scores at 24, 48 and 72 h had lesser number of neonates at each subsequent time point, due to deaths occurring before each of these time points.

The mixed model analysis studied the fixed effect of time and mortality by day 14 on serial SNAP II scores (how the scores have changed) and random effects of study subjects (how the change in SNAP scores varied between study subjects). Hence, mortality by 14 d (outcome of the study) was modelled as a predictor variable (otherwise called an independent variable).

The correspondence authors are right that we should have added mean (SD) next to the gestation and birth weight rows in Table 1 and median (IQR) next to those appropriate rows in Table 2. The p-value for categorical variables was calculated using the Chi-squared test with Yates correction.

The survivors had a greater and more consistent fall in the SNAP-II scores than non-survivors. However, this change was not statistically significantly different. Possible reasons could be a lesser sample size contributing to the model at each subsequent point of SNAP-II measurement. Moreover, unknown features/variables, which were not modelled, could also have modified the change in SNAP-II (treatment options, underlying immune regulation state, etc). Hence, we have stated that a more detailed exploration is required in a larger sample size to better understand the role of change in SNAP-II.