HRCT diagnosis of diffuse parenchymal lung disease: inter-observer variation

High-resolution chest tomography in idiopathic pulmonary fibrosis and nonspecific interstitial pneumonia: utility and challenges

PURPOSE OF REVIEW

High-resolution computed tomography (HRCT) scan is regarded as the imaging modality of choice to evaluate patients with known or suspected interstitial lung disease. With current technology, HRCT allows for detailed assessment of interstitial compartments. We examine recent data on its role in the diagnostic evaluation, clinical decision-making, and prognosis of patients with interstitial lung disease, and we highlight the challenges related to its application in this field.

RECENT FINDINGS

HRCT findings are either diagnostic or strongly suggestive of underlying pathologic patterns. By identifying the presence of certain characteristics, radiologists have developed a clearer understanding of HRCT patterns that coincide with underlying pathology. Challenges and controversies still remain, however. For example, recent studies indicate that the diagnostic accuracy and performance characteristics of HRCT depend predominantly on the study setting; intra-observer and inter-observer variability are less between academic radiologists than between community radiologists. Despite this, clinicians tend to rely primarily on HRCT when a radiologic pattern characteristic for histologic usual interstitial pneumonia is identified.

SUMMARY

Specific HRCT patterns help to differentiate and prognosticate different interstitial lung diseases. It is important for clinicians to understand the utility and limitations of HRCT in managing their patients. A multidisciplinary approach remains the gold standard.

Lung cancer: interobserver agreement on interpretation of pulmonary findings at low-dose CT screening

PURPOSE

To evaluate agreement among radiologists on the interpretation of pulmonary findings at low-dose computed tomographic (CT) screening examinations for lung cancer.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. HIPAA guidelines were followed. Sixteen radiologists from the 10 National Lung Screening Trial screening centers of the National Cancer Institute's Lung Screening Study network reviewed image subsets from 135 baseline low-dose screening CT examinations in 135 trial participants (89 men, 46 women; mean age, 62.7 years +/- 5.4 [standard deviation]). Interpretations were classified into one of four of the following categories: noncalcified nodule 4 mm or larger in greatest transverse dimension (positive screening result); noncalcified nodule smaller than 4 mm in greatest transverse dimension (negative screening result); calcified, benign nodule (negative screening result); or no nodule (negative screening result). A recommendation for follow-up evaluation was obtained for each case. Interobserver agreement was evaluated by using the multirater kappa statistic and by using response frequencies and descriptive statistics.

RESULTS

Multirater kappa values ranged from 0.58 (for agreement among all four classifications; 95% confidence interval: 0.55, 0.61) to 0.64 (for agreement on classification as a positive or negative screening result; 95% confidence interval: 0.62, 0.65). The average percentage of reader pairs in agreement on the screening result per case (percentage agreement) was 82%. There was wide variation in the total number of abnormalities detected and classified as pulmonary nodules, with differences of up to more than twofold among radiologists. For cases classified as positive, multirater kappa for follow-up recommendations was 0.35.

CONCLUSION

Interobserver agreement was moderate to substantial; potential for considerable improvement exists. Clinical trial registration no. NCT00047385.

Recent advances in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) remains the most common of the idiopathic interstitial pneumonias and portends a poor prognosis. Significant strides have been made in the approach to diagnosis and in the ability to predict outcome in the last few years. Advances in high-resolution CT (HRCT) scanning have allowed an accurate diagnosis obviating the need for surgical biopsy in many patients. Furthermore, HRCT scanning may aid in determining prognosis and identifying disease progression. The appropriate use of the HRCT scan requires a multidisciplinary iterative approach incorporating all available data to reach a final diagnosis. However, there remains great heterogeneity in disease progression. Pulmonary hypertension and acute exacerbations of IPF negatively influence prognosis and are increasingly a target of therapy. There has been an increase in the number of well-designed clinical trials of IPF that have focused on more specific targets. While no cure has yet been found, each trial expands our understanding regarding the natural course of the disease and the impact of targeted therapy. In the interim, lung transplantation, which appears to improve survival in a subset of IPF patients, remains the only intervention. The objective of this article is to review advances in the understanding of IPF and the evidence for the findings outlined above.

Is there a uniform approach to the management of diffuse parenchymal lung disease (DPLD) in the UK? A national benchmarking exercise

Background

Benchmarking is the comparison of a process to the work or results of others. We conducted a national benchmarking exercise to determine how UK pulmonologists manage common clinical scenarios in diffuse parenchymal lung disease (DPLD), and to determine current use and availability of investigative resources. We compared management decisions to existing international guidelines.

Methods

Consultant members of the British Thoracic Society were mailed a questionnaire seeking their views on the management of three common scenarios in DPLD. They were asked to choose from various management options for each case. Information was also obtained from the respondents on time served as a consultant, type of institution in which they worked and the availability of a local radiologist and histopathologist with an interest/expertise in thoracic medicine.

Results

370 out of 689 consultants replied (54% response rate). There were many differences in the approach to the management of all three cases. Given a scenario of relapsing pulmonary sarcoidosis in a lady with multiple co-morbidities, half of respondents would institute treatment with a variety of immunosuppressants while a half would simply observe. 42% would refer a 57-year old lady with new onset DPLD for a surgical lung biopsy, while a similar number would not. 80% would have referred her for transplantation, but a fifth would not. 50% of consultants from district general hospitals would have opted for a surgical biopsy compared to 24% from cardiothoracic centres: this may reflect greater availability of a radiologist with special interest in thoracic imaging in cardiothoracic centres, obviating the need for tissue diagnosis. Faced with an elderly male with high resolution CT thorax (HRCT) evidence of usual interstitial pneumonia (UIP), three quarters would observe, while a quarter would start immunosuppressants. 11% would refer for a surgical biopsy. 14% of UK pulmonologists responding to the survey revealed they had no access to a radiologist with an interest in thoracic radiology.

Conclusion

From our survey, it appears there is a lack of consensus in the management of DPLD. This may reflect lack of evidence, lack of resources or a failure to implement current guidelines.

Transbronchial Biopsy Interpretation in the Patient With Diffuse Parenchymal Lung Disease

Context.—The most common lung tissue samples seen by pathologists worldwide are obtained with the flexible bronchoscope. Specimens taken for examination of diffuse or multifocal parenchymal lung abnormalities pose special challenges for the general surgical pathologist, and these challenges are often compounded by high clinical expectations for accurate and specific diagnosis.

Objective.—To present and discuss the most common histopathologic patterns and diagnostic entities seen in transbronchial biopsy specimens in the setting of diffuse or multifocal lung disease. Specifically, acute lung injury, eosinophilic pneumonia, diffuse alveolar hemorrhage, chronic cellular infiltrates, organizing pneumonia, alveolar proteinosis, sarcoidosis, Wegener granulomatosis, intravenous drug abuse-related microangiopathy, Langerhans cell histiocytosis, and lymphangioleiomyomatosis are presented. Clinical and radiologic context is provided for the more specific diagnostic entities.

Data Sources.—The published literature and experience from a consultation practice.

Conclusions.—The transbronchial biopsy specimen can provide valuable information for clinical management in the setting of diffuse or multifocal lung disease. Computed tomographic scans are useful for selecting appropriate patients to undergo biopsy and in limiting the differential diagnosis. Knowledge of the clinical context, radiologic distribution of abnormalities, and histopathologic patterns is essential. With this information, the surgical pathologist can substantially influence the diagnostic workup and help guide the clinician to an accurate clinical/radiologic/pathologic diagnosis.

[Idiopathic interstitial pneumonias: from classification to diagnostic work-up]

Idiopathic interstitial pneumonias (IIP) comprise seven entities with distinct histologic patterns. In their idiopathic form IIP are rare diseases. They are, nevertheless, considered prototypes of the much more common secondary interstitial pneumonias. The advent of high-resolution computed tomography (HRCT) has had a profound impact on the imaging of IIP, because the detailed delineation of the lung anatomy allows a close correlation between the histologic patterns of IIP and the CT features. On the basis of CT morphology and in the correct clinical context, the radiologist can achieve an accurate diagnosis in many cases. However, due to overlap between the various entities, complementary lung biopsy is recommended in virtually all cases. This article reviews the CT pattern of IIP and offers relevant clinical and histological information for the purpose of enabling the radiologist to understand and participate in the multidisciplinary concept of IIP.

Clinical review: Idiopathic pulmonary fibrosis—Past, present and future

Idiopathic pulmonary fibrosis (IPF) is an important, and devastating, interstitial lung disease. It has a median mortality of only 3 years, worse than many cancers, and its incidence continues to rise. In this article, an overview of key developments in our understanding and clinical management of IPF will be provided.

Interstitial lung disease?the new synergy between radiology and pathology

In the last 30 years, high-resolution computed tomography (HRCT) has been the major advance in diagnosis of diffuse parenchymal lung disease (DPLD). We review the diagnostic accuracy of HRCT and discuss how the gold standard in diagnosis of DPLD has shifted from histopathological diagnosis in isolation to a multidisciplinary approach. This latter process is now accepted as providing the highest levels of diagnostic accuracy in patients with DPLD and lung biopsy is primarily reserved for cases with atypical clinical or radiological presentations.

Automated classification of hyperlucency, fibrosis, ground glass, solid, and focal lesions in high-resolution CT of the lung

An automatic method for textural analysis of complete HRCT lung slices is presented. The system performs classification of regions of interest (ROIs) into one of six classes: normal, hyperlucency, fibrosis, ground glass, solid, and focal. We propose a novel method of automatically generating ROIs that contain homogeneous texture. The use of such regions rather than square regions is shown to improve performance of the automated system. Furthermore, the use of two different, previously published, feature sets is investigated. Both feature sets are shown to yield similar results. Classification performance of the complete system is characterized by ROC curves for each of the classes of abnormality and compared to a total of three expert readings by two experienced radiologists. The different types of abnormality can be automatically distinguished with areas under the ROC curve that range from 0.74 (focal) to 0.95 (solid). The kappa statistics for intraobserver agreement, interobserver agreement, and computer versus observer agreement were 0.70, 0.53+/-0.02, and 0.40+/-0.03, respectively. The question whether or not a class of abnormality was present in a slice could be answered by the computer system with an accuracy comparable to that of radiologists.

Inflammatory activity is still present in the advanced stages of idiopathic pulmonary fibrosis

OBJECTIVE

The role of active inflammation in idiopathic pulmonary fibrosis (IPF) is controversial. A gallium-67 citrate (Ga(67) scan) is a sensitive indicator of inflammatory activity. The aim of this study was to assess the Ga(67) uptake and other markers of inflammation at different stages of IPF and to investigate its prognostic role.

METHODOLOGY

Twenty-two patients (aged 66 +/- 11 years, 18 males) with IPF were monitored for a period of 6-20 months (mean 13 months). At presentation (T0), high resolution CT (HRCT) scans showed reticular opacities and traction bronchiectasis with bi-basilar and peripheral distribution in all cases. At both T0 and follow-up (T1), we measured pulmonary function (PaO(2), FVC, DLco), overall radiographic extent of fibrosis (HRCT visual score), Ga(67) uptake, serum concentrations of lactate dehydrogenase (LDH) and C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR).

RESULTS

All parameters showed a significant deterioration during the T0-T1 interval, though the increase in Ga(67) uptake and serum markers was not significant. Patients with Ga(67) uptake indices graded as normal or mildly increased (group I), and graded as considerably or severely increased (group II) at presentation, were compared. There was no significant difference with respect to lung function or HRCT score between the two groups at T1. Ga(67) uptake, LDH, CRP and ESR at presentation did not correlate significantly with the interval change in pulmonary function and disease extent.

CONCLUSIONS

Our findings indicate that inflammatory activity in the advanced stage of IPF is still relevant, although a Ga(67) scan is not predictive of the clinical course.

Functional predictors of exertional dyspnea, 6-min walking distance and HRCT fibrosis score in idiopathic pulmonary fibrosis

BACKGROUND

Exertional dyspnea and exercise incapacity are the most prominent and disabling symptoms and the main contributors to health-related quality of life in patients with idiopathic pulmonary fibrosis (IPF).

OBJECTIVES

There are no comprehensive studies on pulmonary function tests (PFTs), dyspnea, exercise capacity and radiographic scores in IPF. We therefore sought to investigate the functional variables that can predict dyspnea, exercise capacity and disease extent in IPF.

METHODS

Thirty-four patients with IPF according to the ATS/ERS criteria underwent PFTs, Medical Research Council (MRC) dyspnea scoring, 6-min walking distance (6-MWD) and radiographic evaluation of fibrosis (HRCT score).

RESULTS

The 6-MWD (% pred.) was more impaired than PFTs. Residual volume (RV) showed the best correlation with the extent of fibrosis (r = -0.67, p = 0.0001) and, together with the alveolar-arterial gradient for O(2) [DeltaP(A - a)O(2)], was an independent predictor of disease extent (R(2) = 0.44). PFTs showed significant though weak correlations with MRC score and 6-MWD. According to the regression analysis, DL(CO) and the HRCT fibrosis score were independent predictors of dyspnea, though they explained only 28% of the overall variance. FEV(1) and DeltaP(A - a)O(2) were independent predictors of 6-MWD (R(2) = 0.31).

CONCLUSIONS

PFTs and lung volumes in particular are closely related to the HRCT score, a measure of the extent of IPF. The correlation of dyspnea score and 6-MWD to PFTs is limited, due to the complexity of mechanisms leading to exercise limitation in IPF. Therefore dyspnea and exercise performance are largely independent indices and should be followed together with PFTs and HRCT score in order to better assess the status and progress of IPF patients.

Diagnosis: To Biopsy or Not to Biopsy

Idiopathic pulmonary fibrosis (IPF) is a chronic disorder that is associated with a poorer prognosis than subacute idiopathic interstitial pneumonias (IIPs). IPF can be differentiated from other IIPs on the basis of its histologic pattern of usual interstitial pneumonia (UIP). Although a surgical lung biopsy specimen showing a UIP pattern is required for the definitive diagnosis of IPF, clinical criteria can be used in the absence of a lung biopsy specimen to make a likely diagnosis of IPF. The predictive value of these criteria largely depends on the expertise of the clinician and radiologist, but considerable interobserver variability exists even when evaluations are performed by experts in the field. Moreover, these criteria lead to misdiagnosis in about 25 to 35% of cases. Interobserver variability is reduced and diagnostic accuracy is improved in cases in which a diagnosis is made with a high degree of confidence. Diagnostic accuracy is also higher when the diagnosis is made by a core group of experts rather than by a referring center. The decision on whether or not to perform a surgical lung biopsy is difficult. It is clearly indicated in cases in which clinical or radiologic findings are atypical or when the diagnosis is made with a low degree of certainty.

High-Resolution Computed Tomography in Idiopathic Pulmonary Fibrosis

RATIONALE

High-resolution computed tomography (HRCT) is an integral aspect of the evaluation of patients with suspected idiopathic pulmonary fibrosis (IPF). However, few studies have evaluated its use in a large cohort.

OBJECTIVES

To describe HRCT features in patients with mild to moderate IPF, compare diagnostic evaluations by a radiology core (three thoracic radiologists) with those by study-site radiologists, correlate baseline clinical and physiologic variables with HRCT findings, and evaluate their association with mortality.

METHODS

We assessed HRCT scans from patients with IPF (n = 315) enrolled in a randomized controlled study evaluating IFN-gamma1b.

MEASUREMENTS AND MAIN RESULTS

There was concordance between study-site and core radiologists regarding the diagnosis of IPF in 86% of cases. Diffusing capacity of carbon monoxide (DLCO) was the physiologic characteristic most highly correlated with HRCT findings. Multivariate analysis identified three independent predictors of mortality: a higher extent of fibrosis score increased the risk of death (p < 0.0001), whereas a higher percent-predicted DLCO (p = 0.004) and treatment assignment to IFN-gamma1b rather than placebo (p = 0.04) reduced the risk of death.

CONCLUSIONS

A study-site diagnosis of IPF on HRCT was regularly confirmed by core radiologists. Extent of reticulation and honeycombing on HRCT is an important independent predictor of mortality in patients with IPF.

Clinical advances in the diagnosis and therapy of the interstitial lung diseases

The last century experienced remarkable advances in the classification, diagnosis, and understanding of the pathogenesis of the interstitial lung diseases. Technological advances, particularly physiologic testing, lung imaging studies, bronchoalveolar lavage, surgical lung biopsy, and histopathologic assessment, improved our understanding of these entities. In particular, the advent of high-resolution computed tomography, the narrowed pathologic definition of usual interstitial pneumonia, and recognition of the prognostic importance of separating usual interstitial pneumonia from other idiopathic interstitial pneumonia patterns have profoundly changed the approach to these processes. Most recently, genetic medicine, the use of new technologies (e.g., microarrays, mass spectroscopic analysis of proteins, and laser capture microdissection), and the development of animal models have had a major impact on understanding the pathogenesis and potential molecular targets for interfering with fibrogenesis. This article highlights some of the advances and changes in clinical practice that took place in the management of patients with interstitial lung diseases over the last century.

Do High-Resolution CT Findings of Usual Interstitial Pneumonitis Obviate Lung Biopsy?

BACKGROUND

High-resolution CT (HRCT) of the lungs has become an essential component to evaluate patients with diffuse lung disease. Little is known, however, about the current practices of pulmonologists caring for patients with these complex conditions, and, in particular, whether HRCT can obviate the need for surgical lung biopsy.

OBJECTIVES

To investigate the practices of pulmonologists concerning the acceptability of a HRCT diagnosis in lieu of lung biopsy in diffuse lung disease.

METHODS

We asked practicing pulmonologists among membership of the American College of Chest Physicians whether HRCT results could replace lung biopsy in 16 diffuse lung diseases. Responses were examined in light of published evidence, practice guidelines, and certain practice parameters.

RESULTS

Two hundred and thirty (52.6%) of 437 eligible physicians responded. Sixty-seven percent (67%) of respondents accepted HRCT diagnosis for idiopathic pulmonary fibrosis/usual interstitial pneumonia (IPF/UIP) despite their awareness of guidelines recommending histological diagnosis. Most would not accept a radiologic diagnosis for lymphangioleiomyomatosis (LAM; 37%) or eosinophilic granuloma (Langerhans' cell histiocytosis, LCH; 19%), even though CT findings are frequently characteristic. Responses were similar by type of clinical practice and recency of fellowship training. Chest physicians who referred patients for HRCT more frequently were more likely to accept HRCT diagnosis (p=0.008) and those who had higher self-ratings of proficiency in reading HRCT (p = 0.004) were more likely to believe HRCT often suggests specific diagnosis.

CONCLUSIONS

Most US pulmonologists will accept an HRCT diagnosis of IPF/UIP without lung biopsy, but are reluctant to do so for most other diffuse lung conditions including LAM and LCH.

VATS lung biopsy: the uniportal technique

Presentation of the uniportal VATS technique for lung biopsy: through a single port incision, a videothoracoscope, a lung grasper, and a roticulating endostapler are introduced into the pleural cavity. Based on the preoperative CT findings, the target areas are addressed from a cranio-caudal perspective instead of from a lateral one. Multiple wedge resections of different sizes can be obtained and the specimens removed through the same port.