The etiology of interstitial lung disease (ILD) is highly varied. Currently, >150 different causes are known, and it is possible to identify the causal agent only in approximately 35% of the cases. Overall, idiopathic pulmonary fibrosis (IPF) is the most common interstitial pneumonia.1
A definitive and specific diagnosis of ILD might require a histologic analysis of the lung parenchyma. A traditional transbronchial biopsy (TBB) is useful for diseases with lymphatic and centrolobular distribution or for those presenting with characteristic diagnostic features and having a diffuse but low distribution of idiopathic diffuse interstitial lung disease during diagnosis because patient samples are small.
The ATS/ERS/JRS/ALAT 2011 official consensus reports typical findings on a chest high-resolution computed tomography scan (HRCT) for diagnosing usual interstitial pneumonia (UIP). The consensus statement recommends that if an HRCT does not reveal a pattern typical of UIP, a surgical biopsy must be considered. A correct diagnosis is of paramount importance because of the resulting important prognostic and therapeutic consequences of the diagnosis. A multidisciplinary evaluation leads to an increased diagnostic accuracy and is currently considered as the gold standard.2 In other ILDs, if clinical or radiologic data are not conclusive or other conditions, such as medico-legal problems, are present, a histologic diagnosis may also be necessary.
Assessment of the histologic material obtained by cryoprobes in cases of endobronchial lesions in which a larger-sized specimen was verified is the starting point to use a transbronchial lung cryobiopsy (TBLC) as an alternative to the traditional method.3,4 Incorporation of this technique to diagnose ILD appears very promising. However, currently, there are not many studies published on this topic.5–14
Our paper shows the results since TBLC implementation in 2012 in our center obtained prospectively with a TBLC using a flexible cryoprobe for an ILD diagnosis.
PATIENTS AND METHODS
A descriptive prospective study was conducted with all patients with ILD and a nonconclusive diagnosis from January 2012 to January 2015 in which a final indication of using a TBLC had been made in our center.
All cases were evaluated first by a multidisciplinary team composed of pneumologists, thoracic surgeons, and radiologists. After each biopsy, the samples were reevaluated by the same team, but with the added presence of lung pathologists.
Inclusion criteria (final indication of TBLC) were as follows: (a) the presence of ILD and a nonconclusive clinical-radiologic diagnosis; (b) histologic confirmation required (medico-legal requirement or prognostic and treatment decisions); (c) signed informed consent (IRB approved).
Exclusion criteria included (a) age >75 years and (b) the presence of a limiting severe comorbidity.
All patients underwent a routine structured diagnostic algorithm that included the following: (a) detailed history, including drugs and occupational exposure, and full physical examination; (b) spirometry, plethysmographic lung-volume measurement, and tests for the diffusing capacity of the lung for carbon monoxide (DLCO); (c) chest HRCT; (d) laboratory blood testing, which included angiotensin-converting enzyme and autoimmunity markers (ANA, RF, and, in selected cases, AntiScl-70, anti-tRNA syntase antibodies, anti-Ro, anti-RNP, and anti-CCP); (e) coagulation test (International normalized ratio<1.5; platelets level >100.000/mm3).
Tests were performed in the operating room with general anesthesia. A radiologic follow-up was performed 4 to 6 hours after completing the procedure, before hospital discharge (if early complication was suspected, it was performed immediately).
A biopsy site was selected by an endoscopist according to an HRCT. Endotreacheal intubation was performed (nonring tubes with caliber 8 to 8.5 mm) by an anesthetist who also placed a balloon catether into the trachea (Olympus Model No. BF26), which was subsequently located under endoscopic control in the bronchus at the planned location of the samples. A standard bronchoscope (Olympus Model No. BF-160) was used to conduct an airway exam and BAL. After each BAL, an ampule of 1 mg/mL of adrenaline diluted into 9 mL of physiological saline solution was instilled in the selected segment. A large-channel (Olympus XT-160) video bronchoscope was used, and a cryoprobe (Erbokryo CA, ERBE, Germany) with a diameter of 2.4 and 900 mm in length was inserted by means of the working channel of the flexible bronchoscope. Biopsies were performed under fluoroscopic control with the tip guided to a 1.0 to 1.5-cm subpleural position. The cryoprobe was cooled down for 3 to 4 seconds using liquid nitrous oxide. Frozen tissue attached to the probe’s tip was removed by pulling the cryoprobe together with the bronchoscope, followed by immediate inflation of the catheter balloon. Although an assistant personnel collected the sample, another video bronchoscope was used to verify the presence of bleeding after deflating the balloon, and the examination was continued. Besides the onset of complications, we attempted to obtain at least 2 or 3 biopsies in all cases and always from the same lung.
Complications, such as iatrogenic pneumothorax, postinterventional endobronchial bleeding, and 30- and 90-day postinterventional mortality, were reported. Endobronchial bleeding was classified according to British Thoracic Society guidelines.15 Two endoscopists took part in each examination.
All samples were sent to the department of pathologic anatomy and fixed in 0.4% buffered formalin. The area was measured in mm2 before it was embedded in paraffin. A total of 4 serial sections were stained with hematoxylin and eosin. Histochemical techniques with Masson’s trichrome, Alcian blue, PAS, and Pearl’s stains were also used. Samples were assessed by 2 pathologists who were specialized in respiratory pathology. A sample was considered undiagnosed when insufficient histopathologic features were present to identify a disease. A sample was considered invalid when lung parenchyma was absent from the sample. After a consensual multidisciplinary discussion, diagnoses were classified as certain, highly likely, or unclassifiable interstitial pneumonia.
The statistical package G-Stat 2.0 (ISBN: 84-607-5171-6; RL: M-37418-2002) was used for the statistical analysis. The comparative study between the groups was performed using the χ2 test. A P-value of 0.05 was considered as the limit of statistical significance.
During the study period, we studied 83 patients. Twenty-three of them were rejected by a committee decision (8 because of age >75 y, 7 because of chronic respiratory failure, 4 with known severe myocardiopathy, 2 with cognitive deterioration, and 2 with tumors with a bad prognosis). Five other patients did not give their consent. Finally, TBLC was performed on 55 patients with ILD.
The clinical and functional characteristics are shown in Table 1. The biopsy characteristics are outlined in Table 2. All the patients had at least 1 sample with the existence of viable lung parenchyma for the study. The biopsies were performed in right lower lobe in 40 patients (72.7%), left lower lobe in 6 (10.9%), right upper lobe in 5 (9.0%), and left upper lobe in 4 (7.2%) patients. Figure 1 schematically shows the results obtained with the TBLC. Table 3 shows the final diagnoses after the multidisciplinary consensus. Of the patients with a moderate–high clinical-radiologic suspicion of a specific entity, we found a coincident histologic diagnosis in 41.8% of the patients. However, we reached a definitive diagnosis in 87.5% in the patients without it. Of the 7 cases with undiagnosed surgical samples, a lung biopsy was performed in one with a final diagnosis of UIP. One of these patients was diagnosed with chronic eosinophilic pneumonia after the BAL data were obtained. For the other 5 patients, a surgical biopsy was ruled out because of their comorbidities and other conditioning factors. Of the 55 patients, 6 had an inconclusive TBB using standard forceps. For 5 of the patients, the TBLC was conclusive and provided high probability data.
Of the complications, pneumothorax was the most frequent. It occurred in 8 patients (14.5%). A pneumothorax was detected almost immediately after the biopsy in 3 patients (37.5%): 1 because of reported chest pain and 2 because of oxygen desaturation. Seven patients required a drain, which was discontinued in 6 cases in the first 48 hours. The remaining patient required another 4 days of draining. Bleeding was present in 6 cases (10.9%), always after the balloon was deflated. According to the British Thoracic Society classification,15 4 cases were mild, 1 was moderate, and 1 severe. The global mortality was 0% at 30 and 90 days. Two patients required treatment in the ICU: in 1 case because of serious bleeding (in this case, supportive measures were necessary despite the usual endoscopic treatment for hemoptysis) and another because of a bilateral pneumothorax, although the samples had been taken from only 1 lung.
The mean duration of the procedure from the commencement of anesthesia until the patient was transferred to the recovery room was 58.8 minutes (SD±19.5). The mean hospital stay was 1.8 days (range: 1 to 14, median: 1).
Table 4 shows the diagnostic yield, complications, and the validity of the samples according to the lobe in which the TBLC was performed. Table 5 shows its efficacy according to the number of samples. We did not find a significant relation between the number (>2 vs. ≤2) or the sample size (>20 mm2 vs. ≤20 mm2) and complications (χ2=2.04, P>0.05 and χ2=30.0, P>0.05, respectively). We had balloon displacement in 6 cases (10.9%), needing replacement under endoscopic direct control.
ILD includes a number of heterogenous diseases with different prognostic and therapeutic implications. When the clinical and radiologic contexts are not diagnosed clearly, histology is essential. Although previous use had been reported, a protocol was established by Zavala16 for TBB with standard forceps. The main disadvantage of this technique is its limited diagnostic yield. In a prospective study, Curley and colleagues found that only half of the biopsies performed on 170 patients obtained 2 mm2 sample, and 48% had <15 alveolar spaces. Together with the artifacts associated with using forceps (crushing) and features of the studied pathology studied, this meant that the diagnostic yield in this series was only 14.7%.17 Recently, when comparing the results of a study that aimed to assess the diagnostic efficacy of a TBLC in UIP with those obtained previously by a TBB with standard forceps, Casoni et al5 verified a notable increase in biopsies diagnosed when the former was used. To date, the alternative for diagnostic confirmation in many cases of ILD was an open-lung biopsy using a minithoracotomy or videothoracoscopy, which are more expensive and have more side effects.18–22
Our study highlights the considerable size of samples obtained by a TBLC (mean of 20.7 mm2) with a high percentage of samples valid for the study and the rare occurrence of artifacts. Regarding the test yield, Pajares et al12 discovered that the diagnostic yield of a cryoprobe was better than that obtained with traditional forceps (51% vs. 29%). Our diagnostic percentage was similar or better than that published in other works with this technique.5,8,11,14 Using the 2.4-mm probe against a 1.9-mm probe may have had an impact on our results. There are very few references made in published works to the lung lobes where samples are obtained. The optimal number of samples using a cryogenic probe during the diagnosis of ILD has not been established. Our results suggest (although we studied a small number of patients) that 2 samples obtained in the lung areas that were identified by the HRCT as affected might be sufficient. In 16.3% of our cases, the TBLC was performed on the upper lobes, and we did not find statistically significant differences either in its diagnostic efficacy or in its complications compared with the lower lobes.
As mentioned previously, the size of the samples obtained by means of a TBB with standard forceps indicates that a diagnostic yield is low during the diagnosis of IPF, whereby, if an HRCT does not reveal a pattern of typical certainty, the recommendation to date was to perform a surgical lung biopsy. However, our findings are in line with other studies, such as those by Casoni et al.5 In a prospective study performed on 69 patients with fibrosing ILD in which the HRCT findings were not typical of UIP, Casoni and colleagues obtained good results with a TBLC. In our series, after the corresponding multidisciplinary assessment, UIP was the most common diagnosis (32.7%), representing 36.8% of the cases diagnosed with certainty. These findings are similar to that of other studies.11,13
The test’s viability and safety are other important aspects to consider. Regarding the former, because this is a relatively novel technique and no prior experience is available, we decided to carry out our examinations under safer conditions. All of the procedures were performed under a hospital admission regimen in the operating room with the patient subjected to general anesthesia. This certainly contributes to increasing the complexity and costs of the procedure. A specific limitation of our study was the absence of a cost analysis. Regardless, even with the conditioning factors mentioned, it appears reasonable to think that the cost would be less than for a surgical lung biopsy. As revealed in another study, the cost-effectiveness of the test could be correct.23 Some authors opine that with sufficient experience, the procedure could be performed in a suitably equipped traditional bronchoscopy room without requiring hospital admission, which would certainly contribute to reducing the cost of the procedure.14 In any case, a postbronchoscopy room should always be available with a nursing staff to control and monitor the patient. In this case, the subsequent bronchoscopy observation period before discharge should be no <2 to 3 hours. In our study, 87.2% of the patients remained in the hospital for the day. The average hospitalization was slightly <2 days. Performing the technique is not difficult for pneumologists experienced with bronchoscopy. However, the methodology we used adds complexity and increases the time required to obtain a sample with the TBLC compared with a TBB with standard forceps.
Regarding the complications, a pneumothorax was the most common (14.5%), followed by bleeding (10.9%). Preventive use of the balloon catheter minimized the number of cases of bleeding. Our percentage of cases with a pneumothorax was half that found in previous studies, which varied from 0% to 5% (including a study that performed a TBLC on lung-transplanted patients) up to 28%. This percentage is justified by performing a TBLC only in patients with suspected UIP.3,5–7,10,11,13,14 For all these reasons, we believe that a TBLC is mostly a well-tolerated technique, but it is not free of risks. One case of death has been published.5 Despite this, it is worth recalling that the 90-day mortality after a lung biopsy using surgery is 2% to 10%,18,20 although our cohort may be not representative of other surgical series.
Our results are in line with previous publications and suggest that a correct diagnostic yield can be obtained with a TBLC. This could be a test to consider for ILD diagnostic algorithms. Further studies specifically comparing a TBLC with a surgical lung biopsy should be performed to definitively confirm the findings to date and reveal a better cost-effectiveness relationship with regard to lung biopsies obtained by surgery.23 Some medical societies are working on new IPF algorithms. One point they make in their proposals is that a TBLC could play a role even before an SLB when a histologic diagnosis is needed.
The authors thank Dr Carmen Puzo for her altruistic assistance to implement this technique in our center and the nursing team (RN María Jesús Sola, NA María Armendáriz) and the CHN Departments of Radiology and Anesthesia for their essential collaboration.
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