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Centre of Cardiothoracic Surgery, University Hospital, Coimbra, Portugal
Received 11 September 2007; received in revised form 24 January 2008; accepted 1 February 2008.
* Corresponding author. Address: Centro de Cirurgia Cardiotorácica, Hospitais da Universidade, 3000-075 Coimbra, Portugal. Tel.: +351 239400418; fax: +351 239829674. (Email: antunes.cct.huc{at}sapo.pt).
| Abstract |
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Key Words: Lung biopsy Clinical diagnosis Diffuse parenchymal lung disease Solitary nodules
| 1. Introduction |
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However, the development and refinement of more sophisticated and accurate imaging and diagnostic methods, such as positron emission tomography (PET), high resolution computer tomography (HRCT) and bronchoscopic techniques [1], complemented by minimally invasive diagnostic procedures (image-directed biopsy or fine-needle aspiration), may challenge the usefulness of SLB. Consequently, the value of the biopsy on the diagnosis, treatment and outcome of these patients has become even more controversial [2–5].
The purpose of the present study was: (1) to determine the overall and disease-related accuracy of clinical and imagiological diagnosis; (2) to compare the presumptive clinical/imagiological diagnosis with the histological result of SLB for indeterminate pulmonary lesions/infiltrates; and (3) to evaluate the need and value of the SLB in this setting.
| 2. Material and methods |
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Data were retrospectively retrieved from the patients records and included: demographic material (age, sex, smoking status); clinical assessment (detailed medical, family, occupational, immunological status and drug use history); physiologic results (pulmonary function tests, including spirometry, lung volumes and diffusing capacity of carbon monoxide); imagiological data (standard chest X-ray and CT and HRCT scans); bronchoscopic examination and related procedures (bronchial lavage or transbronchial biopsy); and microbiology culture results.
The ages of the patients ranged from 5 to 84 (mean, 54) years and there was a slight male predominance. Other clinical data are shown in Table 1 .
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Surgical biopsy was performed under general anaesthesia, by video-assisted thoracoscopic surgery (VATS) or a limited open thoracotomy. The site and number of lung biopsy specimens were determined by the findings on the chest X-rays or the CT scans. If there was suspicion of diffuse parenchymal lung disease (DPLD), specimens were obtained in a triangular fashion, 2–3 cm in each margin, whenever possible from two different lobes, including the transition zone between macroscopically normal-appearing parenchyma and macroscopic diseased lung. Areas of obvious severe fibrotic reaction (honeycomb pattern on HRCT scan) were avoided.
For VATS biopsy, 1 or 2 EndoGIA staples (Auto Suture Company Division, U.S. Surgical, Norwalk, Conn) were used to secure the pulmonary margins. For mini-thoracotomy, the lung specimen was excised after clamping proximally, and tissue was secured by a double running suture of 3-0 vicryl. Conversion to lobectomy and local lymphadenectomy was performed in 13 patients after obtaining extemporaneous histopathological results.
Operative morbidity and mortality were recorded.
2.2 Analysis
The presumed diagnosis based on clinical and imagiological findings, made preoperatively, was compared to the histological diagnosis obtained by lung biopsy and categorized as: correct diagnosis (CD), new (incorrect) diagnosis (ND), and inconclusive (INC).
For the final analysis, five major pathological groups were considered: DPLD (occupational, granulomatous disorders, idiopathic interstitial pneumonias and others); primitive neoplasm; metastases; infectious disease; and other lesions.
The validity and accuracy of the clinical diagnosis were investigated. Sensitivity (proportion of individuals with the disease who have a positive test) and specificity (proportion of individuals without the disease who have a negative test) were determined as measures of validity. The predictive value (positive and negative) was also determined to ascertain whether or not an individual has the disease, based on a positive test [8]. The pre-test probability was defined as the probability of the target disease (pathological groups designated) known before the result of the lung biopsy. It was calculated as the proportion of patients with the target disease out of all the patients with that specific presumptive diagnosis (clinical/imagiological), both those with and without the disease [9]. The probability of the target disorder was calculated by the formula: P(D+) = D+/(D+ + D–), where D+ indicates the number of patients with the target disorder and D– indicates the number of patients without the target disorder.
| 3. Results |
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For the analysis specific to this work, we considered six patterns of imagiological presentation (based on chest X-ray/CT/HRCT) and related them to the histological diagnosis (Table 2 ). The DPLD group had a more heterogeneous imagiological pattern and the honeycombing and ground glass were almost specific features of this disease. In the malignancy groups (metastases and primitive neoplasms), the nodular pattern was overwhelming, but in 8 patients with primitive neoplasms the radiological features were mainly reticular/micronodular and associated to undifferentiated or bronchioloalveolar carcinomas. The classical pleural indentation associated with nodular lesions was also almost exclusively present in the malignancy group, especially in primary lung cancer, but was present in only one third of these patients (n = 16).
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SLB was able to define and characterise the most prevalent diseases, such as pulmonary malignancies and DPLD; it reached a definitive diagnosis in 94.8% of patients; 42.6% of the pathological findings were different from the initially proposed diagnosis; 52.6% of the primary lung cancers were detected unexpectedly; in 40.3% of patients with an initial diagnosis of lung metastases, this was excluded; and in 37% of patients with suspicion of DPLD a specific diagnosis could only be made after SLB.
| 4. Discussion |
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In the daily practice, there are two different scenarios presented to the thoracic surgeon. First, there are the patients with diffuse pulmonary infiltrates. Usually referred by chest physicians with a presumed diagnosis of interstitial lung disorder, but where the clinical/radiological evaluation cannot precise the diagnosis, without which the physician is usually reluctant to initiate medical treatment (corticoids or immunosuppressive medication) or alter the treatment instituted. In this case, SLB is merely a diagnostic procedure. Second, are those patients with a SPN or other focal pulmonary lesions and the possibility of malignancy is the main concern. Observation for growth, biopsy and resection are the available options, simultaneously aiming at avoiding delay in the diagnosis and treatment of lung cancer, false negative results, and unnecessary resection of benign lesions. In this situation, SLB is simultaneously a diagnostic and therapeutic procedure.
On the other hand, despite the recent advances in imaging techniques (contrast-enhanced CT, PET, CT + PET) and in the refinement of minimally invasive diagnostic procedures (TTB, TBB), these techniques still have limitations. Although CT scanning is a sensitive imaging technique, it cannot prove malignancy. In multiple series, 25–40% of malignant nodules (SPN) were misclassified as benign [13]. In our study, a correct diagnosis was achieved in only 59% of the SPN. Even in fine-needle aspiration cytology, the sensitivity varies from 71% to 97% and the specificity from 97% to 100% and inadequate samples are obtained in 4–18% of the cases [14]. Despite the already proven applicability of PET (sensitivity and specificity for malignancy were 89–100% and 79–100%, respectively, and diagnostic accuracy ranging from 89% to 100%), false-negatives can occur, most notably in association with bronchioloalveolar carcinoma, carcinoids and in tumours less than 10 mm in diameter. Furthermore, false positives have been reported in active lung diseases such as granulomas, aspergillomas, active tuberculosis and abscesses [15].
Despite the high specificity of the clinical diagnosis, the sensitivity was quite low in our study (except for the metastases group), as was the positive predictive value, meaning that there were a significant number of patients in whom a correct diagnosis would be missed if a lung biopsy was not performed. The high sensitivity for the lung metastases is misleading, because it was a diagnostic hypothesis usually considered in patients with a known history of malignant tumours, hence the probability to miss the diagnosis was minimal. But when we evaluated the probability that a patient had the disease based on a positive test (PPV), the clinical diagnosis was not satisfactory (low PPV), reflecting an important number of false-positives in this group. Conversely, the negative predictive value was very high (99%), reflecting a very small number of false-negatives and resulting in that almost all metastases (except one from a tumour of unknown origin) confirmed by pathological examination were previously presumed by the clinical/radiological evaluation.
Regarding the DPLD group, the result of the positive predictive value (76%) can be deceiving, because this is a heterogeneous group with more than 100 entities and several diagnostic hypotheses were present under the cover of this broad term. In a considerable number of patients (n = 57) with suspicion of having DPLD, a specific diagnosis could only be made after SLB (Fig. 2 ). SLB was also able to distinguish the several clinicopathological entities of idiopathic interstitial pneumonias, in accordance with the definition of the American Thoracic Society and European Respiratory Society [20], discriminating different prognosis (Fig. 3 ).
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We had a high specificity in this group, probably related to the inclusion of focal pulmonary lesions that would practically exclude the diagnosis of DPLD, and a reasonable sensitivity of the clinical evaluation, consistent with other studies. Our experience shows that SLB almost uniformly results in a precise diagnosis. As the classification schemes for DPLD become more complex [20], diagnostic accuracy becomes a more pressing issue.
With regards to focal lesions or SPN, 55% of the nodules excised were malignant, comparable to the incidence reported in the literature [21,22]. Eighteen patients (22%) had primary and 20 (34%) had secondary lung cancer. We were probably overzealous in the approach to these patients, because nearly 45% of the nodules excised were benign, meaning that an observational strategy could have been carried out in some cases.
Finally, there was not a sufficient size sample for the infectious group to draw conclusions about the accuracy of the clinical diagnosis, even though it is important to refer that 15 unexpected diagnoses were made after SLB, mostly from infection with BK, which is still endemic in our country.
Our study has several limitations that deserve further discussion. Firstly, we have coupled two distinct groups of patients (diffuse infiltrates vs focal infiltrates), which could have altered the overall accuracy, especially in respect of the specificity and NPV (high in our study). Secondly, this is a retrospective analysis. All the patients included were referred for SLB and it is difficult to know the real accuracy of the clinical/imagiological evaluation because there surely were patients treated conservatively and others with a correct pathological diagnosis obtained by less invasive diagnostic procedures (TBB, TTB), not included in our study. Thirdly, not all patients originated from inside our institution. Many were referred from other primary and secondary centres and from isolated chest physicians, meaning that the clinical and imagiological observation was not uniform for all patients, with probable impact on accuracy.
In conclusion, SLB is a safe and accurate diagnostic tool for pulmonary infiltrates of unknown aetiology, and, in our opinion, remains the gold standard for undiagnosed or incompletely diagnosed diffuse pulmonary disease.
| Footnotes |
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Presented at the 21st Annual Meeting of the European Association for Cardio-thoracic Surgery, Geneva, Switzerland, September 16–19, 2007. | References |
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This article has been cited by other articles:
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W. Wuyts Surgical lung biopsy is not the golden standard in diagnosis of diffuse parenchymal lung diseases Eur. J. Cardiothorac. Surg., December 1, 2008; 34(6): 1271 - 1272. [Full Text] [PDF] |
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G. F. Coutinho, R. Pancas, J. E. Bernardo, and M. J. Antunes Reply to Wuyts Eur. J. Cardiothorac. Surg., December 1, 2008; 34(6): 1272 - 1272. [Full Text] [PDF] |
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