. Author manuscript; available in PMC: 2021 Feb 18.

Published in final edited form as: J Perinatol. 2020 Aug 13;41(2):255–262. doi: 10.1038/s41372-020-00784-y

Table 3.

Estimate of percent change in antibiotic initiation by interrupted time series analysis

Parameter	Estimate	CI upper limit	CI lower limit	p-value

Low-risk VLBW infants^a
Time (every quarter)	−2.3%	−3.0%	−1.5%	<0.001
Level change with guideline	1.5%	−14.6%	17.6%	0.86
Trend change with guideline	0.7%	−1.7%	3.1%	0.59
Combined change in trend before and after guideline adoption	−1.6%	−3.7%	0.5%	0.13

Low-risk ELBW infants^b
Time (every 6 months)	−1.7%	−2.7%	−0.7%	0.003
Level change with guideline	−39.5%	−72.7%	−6.4%	0.03
Trend change with guideline	−0.26%	−9.1%	8.6%	0.95
Combined change in trend before and after guideline adoption	−1.95%	−10.9%	7.0%	0.67

Time expressed in quarter year with guideline adoption in second quarter of 2017.

Time expressed bi-annually with guideline adoption in first half of 2017. CI, 95% confidence interval; ELBW, extremely low birth weight (birth weight <1,000 grams); VLBW, very low birth weight (birth weight <1,500 grams).