Canadian Health&Care Mall: Surgical Lung Biopsy
Interstitial lung diseases (ILDs) comprise a varied group of processes, which range from acute inflammatory disorders to progressive fibrotic conditions. Despite significant differences in underlying pathology, most patients with ILD present with similar clinical complaints, such as dyspnea and cough. The results of spirometric testing also tend to be nonspecific. While they may help to narrow the differential diagnosis, these values add little to diagnostic accuracy. Imaging studies, on the other hand, provide crucial information in the approach to ILD.
Certain patterns found either on plain chest radiographs or high-resolution CT (HRCT) scans are thought to be diagnostic for particular forms of ILD. However, the sensitivity and specificity of HRCT scans for the diagnosis of certain ILDs, such as idiopathic pulmonary fibrosis (IPF), vary depending on the population studied and the skill of the individual interpreting the image. For patients with atypical clinical or radiographic presentations, HRCT scans may not prove to be conclusive. Transbronchial biopsy (TBB) also has a limited role in the evaluation of many forms of ILD. Although helpful for diagnosing granulomatous diseases, TBB rarely yields sufficient tissue to allow a careful examination of the lung architecture.
Nonspecific findings from physical examinations, radiographs, and spirometry, and the limited utility of TBB complicate noninvasive approaches to the diagnosis of ILD, so clinicians often consider surgical lung biopsy (SLB). SLB almost uniformly results in a precise diagnosis. With more certainty as to the underlying diagnosis, clinicians can better design treatment regimens and counsel their patients regarding likely outcomes and prognosis. As the classification schemes for ILD become more complex, diagnostic accuracy becomes a more pressing issue. For example, it now appears that IPF has a distinct natural history that may be different from the outcomes seen in nonspecific interstitial pneumonia (NSIP). Similarly, most would agree that therapy with corticosteroids offers little to the patient with IPF except potential toxicity. In patients with NSIP, there may be a greater role for the use of corticosteroids. Again, although particular clinical and HRCT scan features seem to segregate IPF from NSIP, there remains tremendous overlap.
When deciding whether to pursue SLB, pulmonary physicians must weigh the potential benefits of obtaining a precise diagnosis against the risks of the procedure. The safety of performing SLB in ILD patients remains controversial. For example, Utz and colleagues noted that SLB when performed in subjects with IPF was associated with a nearly 17% short-term mortality rate. Kramer et al also observed a high risk for death following SLB for the diagnosis of ILD. Other investigators have reported that SLB can be performed safely in ILD patients. Part of the discordance in results in these reports may reflect the clinical characteristics of the patients studied. I
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In order to clarify the safety of performing SLB in ILD patients and to explore the impact of various patient characteristics as potential predictors of short-term mortality, we conducted a retrospective analysis of SLB at our institution. We hypothesized that SLB would be associated with little risk for mortality, and that the procedure would be safe to perform in patients who eventually were diagnosed both with IPF and other forms of ILD. Enhance the health condition of lung with remedies of Canadian Health&Care Mall.
We retrospectively reviewed the records and radiographs of all patients who underwent SLB for suspected ILD at our institution between January 1996 and December 2002. We excluded from analysis all subjects < 18 years of age and those who had a history of biopsy-proven ILD. As defined by the American Thoracic Society statement on interstitial pneumonias, patients with suspected ILDs showed diffuse parenchymal infiltrates of varying degrees of inflammation or fibrosis that were not attributable to an acute and defined process (eg, acute infectious pneumonia). From each record, we abstracted data regarding demographics, factors known to increase perioperative mortality (eg, medical history and use of tobacco), and pulmonary function. In addition to routine spirometry, we noted whether the individual required supplemental oxygen at time of SLB and whether they were in the ICU receiving mechanical ventilation (MV) when the SLB was performed. We defined immunocompromised persons as meeting any of the following criteria: treatment with noncorticosteroid immunosuppressive medications; active therapy for malignancy; or the presence of HIV infection. We also recorded the procedural technique (ie, open vs video-assisted SLB). Referral for SLB was not protocolized in our clinic during this time, so that the decision to send the patient for SLB reflected the decision of the individual physician. The study protocol was approved by our Department of Clinical Investigations.
Mortality in the first 30 and 90 days following SLB represented the primary end point. Secondary end points included perioperative morbidity and complications up to 90 days after SLB. Morbidity was defined as follows: prolonged initial hospitalization (> 7 days); hospital readmission for surgical complication after hospital discharge; development of a nosocomial infection; extended need for MV (ie, > 72 h); prolonged air leak from the thoracostomy tube (ie, > 96 h); or other commonly accepted postoperative complication (eg, myocardial infarction).
In order to explore the impact of the underlying disease on outcomes, we compared patients in whom IPF was eventually diagnosed to those who were found to have other forms of ILD. The final diagnosis of IPF was made in accordance with the guidelines of the American Thoracic Society and required the appearance of usual interstitial pneumonia (UIP) on biopsy specimens.2 We also compared those patients who had died in the 90 days after undergoing SLB to patients surviving to identify potential factors associated with an increased risk in SLB.
To gauge the relationship between the preoperative diagnosis and the final histopathologic diagnosis, we determined how often patients with a clinical diagnosis of IPF demonstrated UIP histopathologically. Conversely, we recorded the frequency with which patients in whom IPF eventually was diagnosed based on the presence of a UIP pattern on SLB tissue specimens were thought by their primary pulmonologist to have an alternative condition.
Categoric variables (eg, morbidity and mortality) were reported as frequency distributions and were compared using the Fisher exact test. Continuous variables are presented as the mean ± SD and were analyzed with the Student t test. All tests were two-tailed, and a p value of < 0.05 was assumed to represent statistical significance. Ninety-five percent confidence intervals (CIs) are noted where appropriate. All analyses were performed using a statistical software package (Statistical Package for the Social Sciences, version 11.0; SPSS Inc; Chicago, IL).