Can a chest x-ray predict the future?
If you work in Neonatology then chances are you have ordered or assisted with obtaining many chest x-rays in your time. If you look at home many chest x-rays some of our patients get, especially the ones who are with us the longest it can be in the hundreds. I am happy to say the tide though is changing as we move more and more to using other imaging modalities such as ultrasound to replace some instances in which we would have ordered a chest x-ray. This has been covered before on this site a few times; see Point of Care Ultrasound in the NICU, Reducing Radiation Exposure in Neonates: Replacing Radiographs With Bedside Ultrasound. and Point of Care Ultrasound: Changing Practice For The Better in NICU.This post though is about something altogether different.
If you do a test then know what you will do with the result before you order it.
If there is one thing I tend to harp on with students it is to think about every test you do before you order it. If the result is positive how will this help you and if negative what does it tell you as well. In essence the question is how will this change your current management. If you really can’t think of a good answer to that question then perhaps you should spare the infant the poke or radiation exposure depending on what is being investigated. When it comes to the baby born before 30 weeks these infants are the ones with the highest risk of developing chronic lung disease. So many x-rays are done through their course in hospital but usually in response to an event such as an increase in oxygen requirements or a new tube with a position that needs to be identified. This is all reactionary but what if you could do one x-ray and take action based on the result in a prospective fashion?
What an x-ray at 7 days may tell you
How many times have you caught yourself looking at an x-ray and saying out loud “looks like evolving chronic lung disease”. It turns out that Kim et al in their publication Interstitial pneumonia pattern on day 7 chest radiograph predicts bronchopulmonary dysplasia in preterm infants.believe that we can maybe do something proactively with such information.
In this study they looked retrospectively at 336 preterm infants weighing less than 1500g and less than 32 weeks at birth. Armed with the knowledge that many infants who have an early abnormal x-ray early in life who go on to develop BPD, this group decided to test the hypothesis that an x-ray demonstrating a pneumonia like pattern at day 7 of life predicts development of BPD. 
The patterns they were looking at are demonstrated in this figure from the paper. Essentially what the authors noted was that having the worst pattern of the lot predicted the development of later BPD. The odds ratio was 4.0 with a confidence interval of 1.1 – 14.4 for this marker of BPD. Moreover, birthweight below 1000g, gestational age < 28 weeks and need for invasive ventilation at 7 days were also linked to the development of the interstitial pneumonia pattern.
What do we do with such information?
I suppose the paper tells us something that we have really already known for awhile. Bad lungs early on predict bad lungs at a later date and in particular at 36 weeks giving a diagnosis of BPD. What this study adds if anything is that one can tell quite early whether they are destined to develop this condition or not. The issue then is what to do with such information. The authors suggest that by knowing the x-ray findings this early we can do something about it to perhaps modify the course. What exactly is that though? I guess it is possible that we can use steroids postnatally in this cohort and target such infants as this. I am not sure how far ahead this would get us though as if I had to guess I would say that these are the same infants that more often than not are current recipients of dexamethasone.
Would another dose of surfactant help? The evidence for late surfactant isn’t so hot itself so that isn’t likely to offer much in the way of benefit either.
In the end the truth is I am not sure if knowing concretely that a patient will develop BPD really offers much in the way of options to modify the outcome at this point. Having said that the future may well bring the use of stem cells for the treatment of BPD and that is where I think such information might truly be helpful. Perhaps a screening x-ray at 7 days might help us choose in the future which babies should receive stem cell therapy (should it be proven to work) and which should not. I am proud to say I had a chance to work with a pioneer in this field of research who may one day cure BPD. Dr. Thebaud has written many papers of the subject and if you are looking for recent review here is one Stem cell biology and regenerative medicine for neonatal lung diseases.Do I think that this one paper is going to help us eradicate BPD? I do not but one day this strategy in combination with work such as Dr. Thebaud is doing may lead us to talk about BPD at some point using phrases like “remember when we used to see bad BPD”. One can only hope.