Patients that present with a spontaneous pneumothorax (SP) without a known medical history of lung disease are usually diagnosed as primary spontaneous pneumothorax – a pneumothorax that occurs without underlying diseases. However, underlying diffuse cystic lung diseases such as Birt-Hogg-Dube syndrome (BHD), lymphangioleiomyomatosis (LAM) and pulmonary Langerhans cell histiocytosis (PLCH) may have a spontaneous pneumothorax as their first symptom. In their new study, Gupta et al. (2016) evaluate the cost-effectiveness of high resolution computed tomographic (HRCT) chest imaging for early diagnosis of LAM, BHD, and PLCH in patients presenting with an apparent primary SP. In their analysis the authors show that HRCT image screening for BHD, LAM and PLCH in patients with apparent primary SP is cost-effective and suggest that clinicians should consider performing a screening HRCT in these patients.
Even though an expert radiologist can very accurately diagnose PLCH, LAM, and BHD based on HRCT analysis alone (Gupta et al., 2015), routine CT chest imaging is not currently recommended in patients presenting with a spontaneous pneumothorax (Baumann et al., 2001). The authors compared using HRCT screening followed by pleurodesis in patients with LAM, BHD, or PLCH versus conventional management of SP with no HRCT screening. The authors used a Markov state-transition model to analyse decision trees and concluded that a strategy using HRCT screening for BHD, LAM and PLCH was cost-effective with a marginal cost-effectiveness ratio of $1,427 per quality adjusted life year (QALY) gained. In their base case analysis, authors attributed a diffuse cystic lung diseases prevalence of 8% among patients presenting with apparent primary SP (5% attributed to BHD, 2.5% to LAM, and 0.5% to PLCH based on literature). As expected, the strategy of HRCT screening became more cost-effective as the prevalence of LAM, BHD, or PLCH among patients presenting with an apparent primary SP increased. HRCT screening remained cost-effective for diffuse cystic lung diseases prevalence as low as 0.01% and below this value the strategy remained more effective but associated with increased cost. Again, as expected, as the ability to diagnose diffuse cystic lung diseases based on HRCT features increased, screening with HRCT became increasingly cost-effective. Primary spontaneous pneumothorax is mostly seen in young patients and secondary spontaneous pneumothorax is seen mainly in elderly patients (Gupta et al., 2000). The median age for development of pneumothorax is 38, 35, and 29 years for BHD, LAM, and PLCH, respectively, yet it is important to note that pneumothoraces also occur in older patients with diffuse cystic lung diseases (Mendez et al., 2004; Toro et al., 2007; Almoosa et al., 2006). Although it is common in elderly patients presenting with a SP to consider an underlying lung disease and perform CT imaging, in younger patients the diagnosis of primary spontaneous pneumothorax is often made without considering an underlying disease or performing CT imaging even though the age range of first pneumothorax in patients with a diffuse cystic lung disease overlaps with that of primary spontaneous pneumothorax. Authors did not perform analysis based on age distribution, however their results indicate that the strategy of HRCT screening remains cost-effective at any disease prevalence above 0.01%, which would very likely be the case for diffuse cystic lung diseases in any age group. Therefore, authors suggest that patients of all ages with an apparent primary SP should undergo a screening HRCT exam to check for the presence of underlying diffuse cystic lung diseases.
In addition to the benefit of early diagnosis of diffuse cystic lung diseases derived from early pleurodesis and prevention of recurrent pneumothoraces, the early diagnosis of LAM, BHD, and PLCH provides other potential benefits. For instance, early detection of BHD would allow patients to be regularly surveilled, allowing for early detection of renal cancer. In addition, identifying the index case of BHD in a family can also allow for screening of asymptomatic family members for the disease. Similarly, early detection of LAM or PLCH can facilitate disease management.
The study has a few limitations acknowledged by the authors such as the assumption in their model that all patients with LAM, BHD, and PLCH will agree to undergo pleurodesis and that all patients with an uncertain diagnosis will agree to have confirmatory testing for diffuse cystic lung diseases. Also, authors used Medicare data as a proxy for costs, so their conclusions may not be valid internationally.
In summary authors showed that HRCT screening for BHD, LAM and PLCH in patients with apparent primary spontaneous pneumothorax is cost-effective and suggest that clinicians should consider applying this strategy so that early diagnosis of diffuse cystic lung diseases can lead to appropriate management approaches.
- Gupta N, Langenderfer D, McCormack FX, Schauer DP, & Eckman MH (2016). Chest Computed Tomographic Image Screening for Cystic Lung Diseases in Patients with Spontaneous Pneumothorax is Cost-effective. Annals of the American Thoracic Society PMID: 27737563