Eliminating chest x-rays

An interesting study was published in the Journal of Maternal-Fetal & Neonatal Medicine entitled, Lung ultrasound completely replaced chest x-ray for diagnosing neonatal lung diseases: a 3-year clinical practice report from a neonatal intensive care unit in China.

Over the course of a 3-year period, clinicians at Beijing Chaoyang District Maternal and Child Healthcare Hospital studied 1,381 newborns admitted to the NICU and compared the diagnosis of respiratory disease using chest x-ray and lung ultrasound.

All kids admitted to the NICU had a lung ultrasound performed on admission to the ICU, if there was a clinical change (improvement or deterioration), as well as repeat lung ultrasound at discharge.

They then compared their ultrasound findings in 269 of the children who had received a chest x-ray at other hospital or as outpatient, before admission to the hospital.

They found that:

1. The chest x-ray was concordant with the lung ultrasound in 176 infants, with an overall agreement rate of 65%
   

2. The chest x-ray misdiagnosed 72 patients, and missed the diagnosis in 21 patients (error rate of 34%)
   

Among these misses were:

1. Transient tahypnea of the newborn (TTN) misdiagnosed as respiratory distress syndrome (RDS), and all of these patients were cured after treatment for TTN
   

2. 19 patients with TTN were misdiagnosed with pneumonia
   

3. 11 cases of pneumonia were missed on chest x-ray but seen on lung ultrasound and cured with appropriate treatment
   

4. Six cases of pneumothorax not seen on chest x-ray but visualized with lung US and confirmed with thoracentesis
   

5. Four cases of pleural effusion missed by x-ray but seen on lung ultrasound and confirmed with thoracentesis
   

6. Enlarged thymus in 12 patients misdiagnosed as atelectasis in 12 patients

They highlighted some interesting cases:

Misdiagnosing enlarged thymus as atelectasis

An otherwise healthy baby admitted to the NICU after birth because of right upper lung atelectasis seen on chest x-ray:

It does appear similar to atelectasis but lung US clearly shows that there is no atelectasis, some B-lines consistent with edema. Anterior chest wall ultrasound clearly shows enlarged thymus.

Chest x-ray missed diagnosis of pneumothorax

Female baby with gestational age of 38 weeks admitted to NICU 2 hours after birth because of distress. Respiratory rate increased at 88, chest x-ray showed signs of respiratory distress syndrome:

Lung ultrasound of the same patient revealed barcode/stratosphere sign on M-mode consistent with pneumothorax, in addition to respiratory distress syndrome. Dyspnea significantly reduced after removal of 30cc of air during thoracentesis:

Pneumonia missed on chest x-ray

Patient admitted to NICU 12 days after birth because of fever and cough. Chest x-ray read as normal:

Lung ultrasound revealed bilateral shred sign consistent with pneumonia:

They conclude that lung ultrasound opens up a "new era of green diagnosis" in which newborns are not exposed to the average of 3-31 chest x-rays during a NICU hospitalization period.

This study makes an extremely strong argument for the exclusive use of lung ultrasound in the NICU. The missed diagnoses and incorrect diagnoses the chest x-rays provided are very concerning, especially given the radiation exposure.

The sensitivity and specificity for neonatal lung ultrasound for pneumonia are over 97%. For pneumothorax it is as high as 100% sensitive and specific, both of which are better than chest x-ray.

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