# Using Late C-reactive Protein Measurement in Transient Tachypnea of the Newborn to Predict Bacteremia and Reduce Blood Sampling Frequency

## TL;DR

The study shows that measuring C-reactive protein later in newborns with breathing issues can predict infections better than early testing, reducing the need for frequent blood draws.

## Contribution

The novel approach of delaying the first blood test and using a single late C-reactive protein measurement to predict neonatal bacteremia is proposed.

## Key findings

- Late CRP measurement (12-24 hours post-admission) is the strongest predictor of neonatal bacteremia.
- Delaying blood tests reduces unnecessary phlebotomy without compromising safety.
- Late CRP outperforms early CRP and other clinical variables in predicting infection.

## Abstract

Background

Frequent blood draws in neonates pose significant challenges, including procedural pain, risk of anemia, and increased healthcare burden. Hospitalized neonates with respiratory distress often undergo multiple blood tests to rule out bacterial infections, despite the low incidence of neonatal bacteremia. C-reactive protein (CRP) levels rise 10-12 hours post-infection, suggesting that early testing may not be optimal for predicting bacteremia. This study evaluates whether delaying the initial blood test and relying on a single blood draw can effectively predict neonatal bacteremia, aiming to reduce unnecessary phlebotomy and improve clinical efficiency.

Methods

This retrospective study included neonates diagnosed with transient tachypnea of the newborn (TTN) at E-Da Hospital from January 2021 to June 2022. Cases with congenital anomalies, unstable vital signs, or maternal infections were excluded. Data on neonatal and maternal characteristics, laboratory findings, and blood culture results were analyzed. Logistic regression, random forest analysis, and penalized regression were used to determine predictors of neonatal bacteremia, with a focus on the timing of CRP measurements.

Results

A total of 406 neonates were included, with 10 cases (2.46%) of positive blood cultures. The mean gestational age was 37.8±2.38 weeks, and the average birth weight was 2935.88±600.08 g. The first CRP (measured at admission) was 0.41±2.67 mg/L, while the second CRP (measured 12-24 hours later) was 4.9±8.13 mg/L. Logistic regression identified the second CRP as the only independent predictor of bacteremia (adjusted odds ratio 1.09; 95% CI 1.03-1.15; p<0.05). In the two-variable random forest model, the second CRP had the highest importance score (0.7524) compared to the first CRP (0.2476). In the penalized regression model, the second CRP exhibited a higher standardized coefficient (+1.48) compared to the first CRP (+0.74), suggesting greater predictive importance after penalization. In the multivariable model incorporating gestational age, birth weight, white blood cell (WBC) count, and premature rupture of membranes (PROM), the late CRP remained the most important predictor (importance score 0.2702), followed by WBC count and birth weight. Mode of delivery and PROM had minimal predictive value.

Conclusion

Delaying the initial blood test and relying on a single blood draw post-birth can effectively predict bacteremia in neonates with TTN, reducing unnecessary phlebotomy and associated risks. This strategy minimizes neonatal pain, prevents iatrogenic anemia, and improves healthcare efficiency without compromising patient safety.