Pneumonia accounts for more pre-school-aged deaths worldwide than do tuberculosis, HIV, and malaria combined. Chest radiographs give risks of ionizing radiation and are not always available in resource-limited areas. Seeking an available, accurate, attractive alternative means of diagnosing lung infections, Pereda and colleagues reviewed studies of the diagnostic accuracy of lung ultrasound for pediatric pneumonia.

Eight studies were deemed adequate for inclusion in the meta-analysis. Study sites had been emergency departments (3), hospital wards (2), a pediatric intensive care unit (1), and neonatal intensive care units (2) in China, Egypt, Italy, and the United States. Combined, the eight studies included 765 children with a mean age of 5 years (range 0-17). The degree of ultrasound training varied between the studies.Compared to chest radiography, ultrasound had a sensitivity of 96% and a specificity of 84% in diagnosing pneumonia. Specificity was higher in inpatient settings than in emergency departments, and specificity was higher with more extensively trained physicians performing the ultrasounds.

The authors point out that ultrasound would only detect consolidations reaching the pleura and that atelectasis appears similar to consolidation on ultrasound. They also report that while extensive training improves specificity, there are data showing that a pediatric resident with seven hours of training can reach high sensitivity (98%) and specificity (95%).

COMMENTARY

Worldwide, pneumonia kills nearly one million children each year.1 Only a third of children with pneumonia receive appropriate antibiotic treatment.1 Global efforts have included improved diagnostic education so that affected children are adequately identified as having pneumonia.

In resource-limited areas, at least, “pneumonia” is typically defined as an acute febrile illness with cough and tachypnea (respiratory rate more than 50 breaths per minute between 2 and 12 months of age and more than 40 between 12 and 60 months of age).2 Focusing on tachypnea as a key diagnostic finding has helped prevent overuse of antibiotics in children with viral respiratory infections while increasing the use of antibiotics for children who actually have bacterial pneumonia. This has been especially useful when laboratory and radiologic support for a pneumonia diagnosis is not available.

Using X-ray as a “gold standard” for the diagnosis of pneumonia, however, several studies have found that tachypnea is neither adequately sensitive nor specific enough to be the main criterion to diagnose pneumonia (and, thus, determine that antibiotic treatment is needed).3,4,5 Ultrasound is increasingly available and affordable at points-of-care where lab testing and X-ray imaging take too long and cost too much to be used. The meta-analysis by Pereda and colleagues gives added support to reliance on ultrasound in diagnosing pediatric pneumonia.

Will ultrasound become widely used to diagnose lower respiratory infection in children? In 2013, a European journal included an article suggesting that lung ultrasound might be “internationally officialized in a near future” to diagnose pediatric pneumonia,6 and an American journal carried an article suggesting that it was “prime time for routine use.”7 Now in 2015, ultrasound is still not routinely used. As Pereda and colleagues suggest, training of the people caring for children will be needed if this tool is to become useful in varied clinical settings.

At the same time, studies of pneumonia diagnosis are hampered by the lack of a true “gold standard” that proves the diagnosis.8 Studies of the validity of ultrasound in diagnosing pediatric pneumonia typically use chest radiographs as the “gold standard” by which the sensitivity and specificity of ultrasound are judged. Ultrasound compares more favorably than does the identification of tachypnea. But, is X-ray truly a gold standard for the diagnosis of pneumonia? Nearly two decades ago, good pediatric radiologists at a major children’s hospital independently read and re-read 40 infant chest films without knowledge of clinical information; the kappa statistic of agreement as to whether or not there was “consolidation” was only 0.91 when the same radiologist saw the same X-ray twice, and only 0.79 for agreement between radiologists.9 Interpretation of X-ray findings is not completely reliable.10

What’s a clinician to do? We should still get good history information and pay attention to vital signs as part of our physical exam. We should be concerned that acutely ill, coughing, febrile children with tachypnea might need antibiotic treatment. And, we should consider learning how to use ultrasound at the bedside to help in diagnosing consolidating lung disease in children. 

REFERENCES

  1. World Health Organization. Pneumonia. http://www.who.int/mediacentre/factsheets/fs331/en/, accessed 5-8-2015.
  2. World Health Organization. Pneumonia. In Pocket Book of Hospital Care for Children, World Health Organization, Geneva, 2013: 86-87.
  3. Shah S, Bachur R, Kim D, Neuman MI. Lack of predictive value of tachypnea in the diagnosis of pneumonia in children. Pediatr Infect Dis J 2010;29:406-409.
  4. Neuman MI, Monuteaux MC, Scully KJ, Bachur RG. Prediction of pneumonia in a pediatric emergency department. Pediatrics 2011;128:246-253.
  5. Wingerter SL, Bachur RG, Monuteaux MC, Neuman MI. Application of the World Health Organization criteria to predict radiographic pneumonia in a US-based pediatric emergency department. Pediatric Infect Dis J 2012;31:561-564.
  6. Don M, Barillari A, Cattarossi L, Copetti R, Italian-Slovenian Group on Lung Ultrasound for Pediatric Pneumonia. Lung ultrasound for paediatric pneumonia diagnosis: Internationally officialized in a near future? Acta Paediatr 2013;102:6-7.
  7. Darge K, Chen A. Ultrasonography of the lungs and pleurae for the diagnosis of pneumonia in children. JAMA Pediatr 2013;167:187-188.
  8. Lynch T, Bialy L, Kellner JD, Osmond MH, Klassen TP, Durec T, Leicht R, Johnson DW. A systematic review on the diagnosis of pediatric bacterial pneumonia: When gold is bronze. PLoS One 2010;5:e11989.
  9. Davies HD, Wang EE, Manson D, Babyn P, Shuckett B. Reliability of the chest radiograph in the diagnosis of lower respiratory infections in young children. Pediatr Infect Dis J 1996;15:600-604.
  10. Williams GJ, Macaskill P, Kerr M, Fitzgerald DA, Isaacs D, Codarini M, McCaskill M, Prelog K, Craig JC. Variability and accuracy in interpretation of consolidation on chest radiography for diagnosing pneumonia in children under 5 years of age. Pediatr Pulmonol 2013;48:1195-1200.