Research and Reports in Pulmonology

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Editorial - Research and Reports in Pulmonology (2021) Volume 2, Issue 1

Comparisons of Prognosis between Surgically and Clinically Diagnosed Idiopathic Pulmonary Fibrosis Using Gap Model


Although a multidisciplinary approach has become an important
criterion for an idiopathic pulmonary fibrosis (IPF) diagnosis,
lung biopsies remain crucial. However, the prognosis of patients
with surgically diagnosed IPF (sIPF) is uncertain. We aimed to
investigate the prognosis of patients with clinically diagnosed
IPF (cIPF) and sIPF. In this retrospective observational study,
the Korean Interstitial Lung Disease Study Group conducted a
national survey to evaluate the clinical, physiological, radiological,
and survival characteristics of patients with IPF from January
1, 2003 to December 31, 2007. Patients were recruited from 54
universities and teaching hospitals across the Republic of Korea.
IPF diagnoses were established according to the 2002 American
Thoracic Society (ATS)/European Respiratory Society criteria
(ERS) guideline. A total of 1685 patients with IPF (1027 cIPF and
658 sIPF) were enrolled. Patients with sIPF were significantly
younger, predominantly female, and nonsmokers (all P < 0.001).
sIPF group had significantly better initial pulmonary function.
The proportion of computed tomography-based honeycomb
findings of patients with cIPF was higher than in those with sIPF
(P < 0.001). A Kaplan-Meier analysis showed that the sIPF group
had a better prognosis (P = 0.001). A survival analysis showed
that age, pulmonary function parameters, pulmonary oxygen
tension, honeycombing change, and combined lung cancer had
a significant influence on patient prognosis. However, there was
no significant difference in prognosis between the cIPF and sIPF
groups after adjusting for GAP (gender, age, physiology) stage.
The patients with sIPF had better clinical features than those with
cIPF. However, after adjusting for GAP stage, the sIPF group
showed similar prognoses as the cIPF group. This study showed
that after adjusting for GAP stage, the prognosis of patients
with IPF is the same regardless of the diagnostic method used.
Idiopathic pulmonary fibrosis (IPF) is the most common form
of idiopathic interstitial pneumonias. IPF is defined as a specific
form of progressive and chronic fibrosing interstitial pneumonia
without a definite cause. It occurs primarily in older patients,
especially in the sixth and seventh decades, and is limited to the
lungs. It is also associated with increasing respiratory symptoms
and irreversible respiratory failure. Although IPF could be
diagnosed clinically in the absence of a surgical lung biopsy, it
was recognised as a distinct clinical entity that was associated with
the histologic pattern of usual interstitial pneumonia (UIP). In
the last few years, the paradigm of diagnosis of IPF has gradually
changed from a situation in which biopsy was the criterion
standard to a complex situation in which the multidisciplinary
approach was necessary. Such approach encompasses clinical,
radiological, and pathologic data. However, surgical biopsy is
still needed for IPF diagnoses because there are cases that cannot
be diagnosed without the histologic pattern. It is well known
that the median survival of patients with IPF is <3 years. To
provide precise prognostic information and timely treatment to
these patients, many predictive models have been investigated.
Previous studies have shown that older age at diagnosis, male
sex, decreased pulmonary function, and impaired exercise
capacity predict a worse outcome in patients with IPF.
However, the prognosis of patients with IPF with a nontypical
computed tomography pattern, who were eventually diagnosed
by surgical lung biopsy examination, was largely unknown.
In 2012, Ley et al reported a simple-to-use GAP (gender, age,
physiology) model for predicting IPF mortality, which is a
scoring and staging system like the one for lung cancer. This
novel model consists of 4 clinical variables: gender (G), age (A),
and 2 pulmonary physiology parameters (P, FVC, and DLCO).
Each variable was assigned 1 to 3 points and then added for
staging; stage I (0–3 points), stage II (4–5 points), and stage III
(6–8 points). The purpose of this study is to evaluate whether
clinically diagnosed IPF (cIPF) and surgically diagnosed IPF
(sIPF) have different characteristics. Furthermore, we aimed
to evaluate the role and effect of surgical biopsy in predicting
prognosis in conjunction with the GAP staging system. According
to the international consensus classification, a surgical lung
biopsy is required for the definitive diagnosis of IPF. However,
a diagnosis of IPF can be considered in the absence of a surgical
lung biopsy specimen if certain major and minor criteria are
met. In such cases, all 4 major criteria and at least 3 of the 4
minor criteria must be satisfied. When a biopsy specimen was
not available, all the major criteria except the last (transbronchial
lung biopsy specimen or bronchoalveolar [BAL] fluid sample
showing no features to support an alternative diagnosis) applied
optionally, and at least 3 of the 4 minor criteria had to be fulfilled.
For patients with a surgical biopsy specimen showing UIP, only
the major criteria were considered relevant. Although a surgical
lung biopsy is required for accurate diagnosis, a patient who was
too old and had a low lung function was diagnosed clinically
at the physician's discretion without undergoing a biopsy.
Additionally, a patient who refused to undergo the surgical lung
biopsy was diagnosed clinically. The Student t test was used
to compare continuous variables, whereas Pearson χ2 test was
used to compare categorical variables. Patients were censored
if they were still alive when last contacted (censored at the
last status date), or had received a lung transplant (censored
at the time of the transplant). Survival time was calculated as
the time since diagnosis. The survival was estimated using the
Kaplan–Meier method models. The log-rank statistic was used
to compare survival among groups. The effect of each variable
on the risk of death after controlling for age, sex, and pulmonary
function (GAP predictive variables) was modelled using the Cox
proportional hazards regression
Author(s): Dimitar Antonov

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