Affiliations: St. Antonius Hospital
Nieuwegein, The Netherlands,
Prince of Wales Hospital
Hong Kong, China
Correspondence to: F. M. N. H. Schramel, MD, PhD, FCCP, Department of Pulmonary Diseases, St. Antonius Hospital, PO Box 2500, 3430 CM Nieuwegein, The Netherlands; e-mail: firstname.lastname@example.org
To the Editor:
Sihoe et al (August 2000)1 described a study in
which they tested the hypothesis that thoracic CT scanning could help
to predict the probability of the occurrence of primary spontaneous
pneumothorax (SP) by detecting lung bullae. Several studies have been
performed concerning the possible relationship of blebs and/or bullae
to the development of recurrent primary SP that do not confirm the
conclusion of Sihoe et al.
Mitlehner et al2analyzed 35 patients with primary SP who
underwent thoracic CT scans. The presence of blebs and/or bullae had no
predictive value for recurrences during follow-up. Smit et
al3studied 101 patients with first-time and recurrent SPs
who underwent thoracic CT scans. In 12 patients, bilateral
pneumothoraces occurred. The percentages of patients who had bullae
among those with first-time SPs and recurrent SPs were not
significantly different, nor was the percentage of bullae that occurred
on the pneumothorax side significantly different compared to those
occurring on the contralateral side. Janssen et al4 could
not demonstrate differences in the presence of blebs and/or bullae
during video-assisted thoracoscopy in patients with first-time or
In patients with COPD, bullae frequently can be detected. A study by
Videm et al5in 303 patients with primary and secondary
SPs showed no significant relationship between the recurrence rate of
SPs and COPD. Independent risk factors for recurrence in 122 patients
with primary SPs were reported as follows: pulmonary fibrosis detected
on chest radiographs; physical characteristics; smoking behavior; and
From these findings, one can conclude that the presence of blebs and/or
bullae in patients with primary SPs has no predictive value for the
future development of recurrences. Therefore, investigations to
diagnose blebs and/or bullae should not influence the choice of
treatment to prevent future recurrences.7 Obviously, Sihoe
et al1 did not review the literature as stated above and
therefore performed a study with a noninteresting study objective.
Sihoe et al1 showed a significant difference in the
occurrence of contralateral SP between patients with or without
contralateral blebs and/or bullae (p = 0.04). Table 1
shows the data in a 2 × 2 manner. The Pearsonχ
2 test was used. However, this test is only
applicable when cells of the 2 × 2 table contain a minimum
frequency, which was not the case in the study by Sihoe et
al.,1 A zero value in one of the four cells invalidates the
test. The results of the test are therefore questionable and may be
biased. Other approaches to test for significance in a 2 × 2 table
(eg, Fisher’s Exact Test) did not show significance.
The conclusions of Sihoe et al1 are based on an incorrect
statistical analysis. Several other studies from the past have shown
that blebs and/or bullae have no prognostic value in predicting future
recurrences of SP and should not be used for selecting the right
therapy. Therefore, we cannot agree with Sihoe et al1 that
the detection of lung bullae by CT scanning in the contralateral lung
in patients with primary SPs could have predictive value for the
recurrence of SP and can be used to select patients for surgery.
We thank Drs. Schramel and Zanen for their interest in our work.
Many of the points they raised in their letter were almost identical to
those of Dr. Marc Noppen1. For the sake of space, we will
not repeat ourselves and readers are asked to refer to our reply to Dr.
Noppen’s letter, in which several issues were fully addressed.
We are well aware of the studies cited by Drs. Schramel and Zanen in
their letter, but we disagree that they amount to definitive proof that
bullae are of no predictive value for the recurrence of primary
spontaneous pneumothorax (PSP). In the article by Mitlehner and
colleagues,2blebs or bullae could be found in 31 of 35
patients with PSP. On follow-up of 32 of the 35 patients for an average
of 32 months, 8 patients (25%) had recurrences of PSP. Although there
was no control group in this study, the recurrence rate was far higher
than would have been expected from the general population. In an
earlier article by Lesur and associates3 studying CT scan
findings in patients with PSP vs healthy individuals matched for age,
sex, and smoking habits, significantly more “emphysematous lesions”
were found in the PSP group.
In the articles by Smit et al4and Janssen et
al5 (Dr. Schramel was a coauthor of both articles), which
looked at CT scan and video-assisted thoracoscopic findings in patients
with PSP, no differences in the bulla morphology could be found in
patients with first-time vs recurrent PSP. The authors argued,
therefore, that bullae have no bearing on PSP recurrence. However, this
conclusion seemed to be based more on their opinion than on evidence.
There were no control groups or follow-up data in either study. This
would be analogous to a cross-sectional study with a small cohort of
smokers in which smoking habits were analyzed. If no significant
correlation could be found between the amount of smoking and the
presence of lung cancer, it could be concluded that smoking was not a
cause of cancer!
Until more knowledge on the pathogenesis of PSP becomes available, the
exact relationship between bullae and PSP is likely to remain
controversial. Scientific knowledge is built up from small additive
increments, and it is important that we should keep an open mind on
this subject and allow new evidence to speak for itself.
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