American Journal of Respiratory and Critical Care Medicine

Fibrosing alveolitis associated with systemic sclerosis (FASSc) has a better prognosis than idiopathic pulmonary fibrosis. In view of recent reports that idiopathic nonspecific interstitial pneumonia (NSIP) has a better prognosis than idiopathic usual interstitial pneumonia (UIP), we classified histologic appearances of surgical lung biopsies performed in 80 patients with FASSc. NSIP (n = 62, 77.5%), subcategorized as cellular NSIP (n = 15) and fibrotic NSIP (n = 47) was much more prevalent than UIP (n = 6), end-stage lung disease (ESL, n = 6), or other patterns (n = 6). There were 25 deaths (NSIP 16/62, 26%; UIP/ESL 6/12, 50%). Five-year survival differed little between NSIP (91%) and UIP/ESL (82%); mortality was associated with lower initial carbon monoxide diffusing capacity (DlCO) and FVC levels (p = 0.004 and p = 0.007, respectively). Survival and serial FVC and DlCO trends did not differ between cellular and fibrotic NSIP. Increased mortality in NSIP was associated with lower initial DlCO levels (p = 0.04), higher BAL eosinophil levels (p = 0.03), and deterioration in DlCO levels during the next 3 years (p < 0.005). We conclude that NSIP is the histopathologic pattern in most patients with FASSc. However, outcome is linked more strongly to disease severity at presentation and serial DlCO trends than to histopathologic findings.

Pulmonary involvement occurs more frequently in systemic sclerosis than in other connective tissue diseases (1) and is a significant cause of morbidity and mortality (2). The most common pulmonary manifestations of systemic sclerosis are fibrosing alveolitis, which occurs in approximately 80%, and pulmonary arterial hypertension, seen in up to 50% of patients (3). We have previously shown (4, 5) that fibrosing alveolitis associated with systemic sclerosis (FASSc) has a better prognosis than lone cryptogenic fibrosing alveolitis (CFA), alternatively termed “idiopathic pulmonary fibrosis” (IPF). The classification of idiopathic interstitial pneumonia has been refined recently (68); the histopathologic pattern of nonspecific interstitial pneumonia (NSIP), now recognized as a subgroup of the idiopathic interstitial pneumonias, has a prognosis intermediate between usual interstitial pneumonia (UIP) and desquamative interstitial pneumonia/respiratory bronchiolitis interstitial lung disease (DIP/RBILD) (913) or cryptogenic organizing pneumonia (14). NSIP is known to occur in collagen vascular disorders (15), but its prevalence and relationship to clinical parameters, response to treatment, and prognosis are not known. In particular, the better prognosis in FASSc, compared with CFA, has not been evaluated in relation to the new histopathologic classification.

The aims of this retrospective study were to examine histopathologic subsets of interstitial pneumonia in systemic sclerosis patients with pulmonary involvement (FASSc), and to compare the prognostic value of histologic classification with that of clinical indices, including pulmonary function tests and bronchoalveolar lavage (BAL) cellularity.

Patients

Between January 1985 and December 1997, 476 patients with systemic sclerosis were investigated at the Royal Brompton Hospital, with surgical lung biopsies performed in 94 patients. It was unit policy that biopsies should be taken when possible, if interstitial lung disease was thought to be clinically significant. In 80 patients, clinical information and histopathologic material was available. Interstitial lung disease was evident on computed tomography (CT) in 78 cases; in two cases, biopsied before CT, pulmonary fibrosis was present on chest radiography. Patients fulfilled American Rheumatism Association preliminary criteria for systemic sclerosis (16); scleroderma was classified as limited or diffuse (17). Patients with overlap syndromes or environmental causes of pulmonary fibrosis (identified by a standardized history) were excluded. Current, ex- (history of smoking at least one cigarette/day for a minimum of 1 year, cessation for at least 3 months), and nonsmokers were identified. Treatment constituted a minimum daily dose of prednisolone of 10 mg, with or without an immunosuppressive agent, or D-penicillamine. Follow-up was obtained to death or to January 31, 2001 (censored in seven cases). The study was approved by the local Ethics Committee.

Pulmonary Function Tests

Pulmonary function tests (PFT), performed using ATS guidelines (18), were expressed as percentage predicted values (19). Spirometric volumes (Ohio water-sealed spirometer; Ohio Instruments, Atlanta, GA) plethysmographic volumes (whole body plethysmograph; Fenyvens and Gut, Basel, Switzerland) and carbon monoxide diffusing capacity (DlCO) (single-breath technique, PK Morgan respirometer; PK Morgan Ltd, Chatham, Kent, UK) were evaluated. “Significant” changes in PFT were defined using ATS and European Respiratory Society (ERS) criteria (20): ⩾ 10% change in VC (or at least ⩾ 200-ml change), ⩾ 15% change in single-breath DlCO (or at least 3 ml/minute/mm Hg). Lesser changes were designated “marginal.” PFTs were categorized to pathophysiologic patterns, per ERS recommendations (19).

BAL

BAL was performed as part of routine clinical management, according to recommended guidelines (21) and previous reports (22, 23). Abnormal BAL percentage values were: neutrophils > 4%; eosinophils > 2%; lymphocytes > 14%.

Histopathologic Classification

Sections stained with haematoxylin and eosin, and elastin van Gieson, were evaluated independently by two histopathologists blinded to clinical data (A. G. N., T. V. C.), according to recognized patterns of interstitial pneumonia (7, 11); differences were resolved by joint review. UIP was distinguished by temporal heterogeneity (variation in age of patchy fibrosis, ranging from fibroblastic proliferation, with abundant plump spindle cells and little intervening collagen, to established fibrosis, characterized by poorly cellular hyalinized collagen). In NSIP, fibrosis and/or inflammation was patchy or diffuse, but temporally uniform; cases were subdivided into cellular NSIP (cellular interstitial pneumonia, little or no fibrosis) and fibrotic NSIP (mature collagen, absent or sparse fibroblasts, with or without derangement of architecture) (15). Appearances of uniform honeycombing and complete loss of lung architecture were designated “end-stage lung.”

Statistical Methods

Analysis was performed using STATA software (Stata Corp., Santa Monica, CA). Data are expressed as means (SD), or medians (ranges), depending on distribution. Group comparisons were made using the Wilcoxon rank-sum test, or chi-squared statistics. Survival was evaluated using proportional hazards regression (24). A p value < 0.05 was considered significant.

Histopathologic Findings

Eighty patients undergoing open or thoracoscopic biopsy made up the study population; 67 were white and 13 were Indian or Afro-Caribbean. The kappa coefficient of agreement between the two histopathologists, for the five histologic subgroups (shown in Table 1)

TABLE 1. Histopathologic diagnosis, according to type of scleroderma and duration of external dyspnea


Histologic Subset

No. of Subjects

Type of Scleroderma
 (Limited/Diffuse)

Mean
 Duration
 of Dyspnea
 at Biopsy
 (mo)
NSIP62 (77.5%)43/1911
UIP6 (7.5%)4/228
ESL6 (7.5%)5/124
Miscellaneous*
6 (7.5%)
4/2
12

*Miscellaneous: respiratory bronchiolitis interstitial lung disease (n = 4), sarcoidosis (n = 1), organizing pneumonia (n = 1).

Definition of abbreviations: NSIP = nonspecific interstitial pneumonia; ESL = end-stage lung disease; UIP = usual interstitial pneumonia.

, was 0.72, indicating good but not excellent interobserver agreement. The most frequent histopathologic pattern was NSIP, observed in 62 of 80 patients (77.5%); NSIP was subcategorized as cellular NSIP (15/62, 24%) and fibrotic NSIP (47/62, 76%). In clinical analyses, patients with UIP (n = 6) and those with end-stage lung (n = 6) were grouped together, making up 12 of 80 patients (15%). The remaining histopathologic patterns, excluded from subsequent clinical analysis, comprised respiratory bronchiolitis–interstitial lung disease (RB-ILD) (n = 4, all current smokers), sarcoidosis in a patient with a past history of sarcoidosis, and organizing pneumonia (OP) in a patient receiving D-penicillamine. NSIP was identified in 30 of 39 patients biopsied before December 1990 (77%), and in 32 of 41 patients biopsied after December 1990 (78%).

Clinical Data

Clinical information in the 74 patients with NSIP or UIP/ESL is shown in Table 2

TABLE 2. Demographic and clinical data at presentation in patients with nonspecific interstitial pneumonia or usual interstitial pneumonia/end-stage lung disease


Age at presentation, median (SD),

yr (range, yr)46 ± 11 (23–69)
Sex: M/F ratio13/61
Smoking history
Current smokers4 (5%)
Exsmokers21 (28%)
Nonsmokers49 (66%)
Duration of respiratory symptoms before13 ± 13
referral (mo: mean ± SD, range)(0–60)
Type of scleroderma
Limited52 (70%)
Diffuse22 (30%)
Respiratory history
Chronic exertional dyspnea66 (89%)
Chronic cough26 (35%)
No respiratory complaints8 (11%)
Respiratory findings
Bilateral predominantly basal crackles63 (85%)
Finger clubbing
2 (3%)
. Patients with nonproductive cough (n = 26), chest pain (n = 8), and wheeze (n = 5) invariably gave a history of chronic exertional dyspnoea. The eight patients with no history of chronic respiratory symptoms had been referred with suspected interstitial lung disease, based on chest radiographic findings and abnormal pulmonary function tests. Evidence of pulmonary hypertension was evident on echocardiography in 12 of 56 patients examined (21%); in 44 patients, echocardiographic findings were normal; and in the remaining 18 patients, there was no evidence of pulmonary hypertension, based on clinical findings and PFT.

PFT in Patients with NSIP or UIP/ESL

At presentation, spirometric and plethysmographic volumes were normal in 23 patients, with abnormalities seen in 51 patients (restrictive pattern, n = 42; obstructive pattern, n = 2; mixed pattern, n = 7). The percentage predicted DlCO (mean ± SD = 51.2 ± 14.5%) was decreased in all but two patients. The percentage predicted FVC (mean ± SD = 75.6 ± 19.5%) was decreased in 43 of 74 patients (58%). Overall, only one patient had normal initial FVC and DlCO levels (> 80% predicted). Among 43 patients with abnormal initial FVC levels, the proportion with NSIP (n = 35, 81%) and UIP/end-stage lung disease (ESL) (n = 8, 19%) did not differ from the proportions of NSIP and UIP/ESL in the whole population. Patients with UIP/ESL had lower DlCO levels than those with NSIP (41.8% ± 11.1% versus 53.1% ± 14.4%, p = 0.01), but FVC levels did not differ significantly between the two subgroups (68.0 ± 28.4% in UIP versus 77.1 ± 17.3% in NSIP, p = 0.14). DlCO and FVC levels at presentation did not differ significantly between cellular and fibrotic NSIP.

BAL Findings in Patients with NSIP and UIP/ESL

BAL data at first presentation were available in 67 of 74 patients with UIP/ESL or NSIP (Table 3

TABLE 3. Bronchoalveolar lavage cell differential (median, range) in usual interstitial pneumonia/end-stage lung disease and nonspecific interstitial pneumonia, with data given separately for cellular and fibrotic nonspecific interstitial pneumonia




UIP/ESL

NSIP

Cellular NSIP

Fibrotic NSIP
Subjects, n10571245
Alveolar macrophages82.57876.579
28–9746–9560–9246–95
Lymphocytes6813.56
1–220–456–300–45
Neutrophils552.56
1–551–411–121–41
Eosinophils2.5435

0–4
0–19
0–10
0–19

Definition of abbreviations: ESL = end-stage lung disease; NSIP = Nonspecific interstitial pneumonia; OP = organizing pneumonia; RB-ILD = respiratory bronchiolitis interstitial lung disease; UIP = usual interstitial pneumonia.

, Figure 1) . BAL eosinophil percentages were higher in NSIP than in UIP/ESL, p = 0.02; BAL neutrophil and lymphocyte levels did not differ significantly between these two subgroups. BAL neutrophil and eosinophil percentages did not differ significantly between cellular and fibrotic NSIP. BAL lymphocyte levels were higher in cellular NSIP than in fibrotic NSIP, p = 0.007 (Figure 2) .

Survival in Patients with NSIP and UIP/ESL

Twenty-two patients (30%) died during a median follow-up of 74.5 months (range, 1–16 years), including 16 of 62 patients with NSIP (26%), and 6 of 12 patients with UIP/ESL (50%; UIP, n = 4; ESL, n = 2). Four patients (5%) developed lung cancer during follow-up (adenocarcinoma, n = 3; small cell lung carcinoma, n = 1); one patient was an exsmoker and three were nonsmokers (all four patients died of the malignancy). Proportional hazards analysis showed that mortality increased with decreasing initial FVC levels (p = 0.007) and decreasing initial DlCO levels (p = 0.004), but did not vary with age, sex, or smoking status (which did not differ significantly between the two groups), or BAL findings (percentage neutrophil, eosinophil, or lymphocyte counts). The pattern of cutaneous involvement (limited versus diffuse scleroderma) was not linked to outcome. Survival did not differ between NSIP and UIP/ESL (p = 0.33), and this finding persisted after controlling for age, sex, and initial FVC and DlCO levels (analyzed in separate models), and when NSIP patients were compared separately with UIP patients (four deaths) and with ESL patients (two deaths). As shown in Figure 3

, 5-year survival was 90% in NSIP and 82% in UIP/ESL. The 10-year survival was 69% in NSIP and 29% in UIP/ESL; the reduction in survival in UIP after 8 years of follow-up, ascribable to three deaths occurring in the small group remaining under follow-up (n = 5), was not statistically significant.

Survival in Patients with NSIP

Survival did not differ significantly between cellular and fibrotic NSIP. Decreasing DlCO levels at presentation were associated with increasing mortality (p = 0.04) but age, sex, and FVC levels were not linked to survival. Survival was re-examined with the inclusion of BAL data, in the 57 patients undergoing BAL. There was a significant association between increasing BAL eosinophil levels and increasing mortality (p = 0.03) (Figure 4)

. BAL neutrophil and lymphocyte and macrophage levels were not linked to mortality. When percent predicted DlCO was included in proportional hazards analysis as a marker of initial disease severity, decreasing DlCO levels (p = 0.04) and increasing BAL eosinophil levels (p = 0.02) were both independently associated with mortality.

Serial Pulmonary Function Indices in NSIP

As shown in Table 4

TABLE 4. Serial changes in percent predicted fvc and dlco levels in patients with nonspecific interstitial pneumonia, one year after presentation (n = 61) and 3 years after presentation (n = 57)




FVC (1 yr)
 (n = 61)

DlCO (1 yr)
 (n = 61)

FVC (3 yr)
 (n = 57)

DlCO (3 yr)
 (n = 57)
Overall change (median)−1.7%−0.3%−2.5%−1.8%
Overall change (range)−25.2 to 30.7%−43.6 to 52.7%−29.6 to 64.2%−44.2 to 43.4%
Significant improvementn = 10 n = 9n = 13n = 12
Significant declinen = 15 n = 8n = 11 n = 8
Change not significant
n = 37
n = 44
n = 33
n = 37

Changes in functional indices are expressed as percentages of values at first presentation, stated as median values with ranges. Numbers of patients with a significant decline or improvement in FVC (change exceeds 10% of baseline) and DlCO (change exceeds 15% of baseline) are shown.

, there was little overall decline in FVC and DlCO levels, 1 and 3 years later, in patients with NSIP, although large changes were observed in individual patients. Trends in FVC and DlCO did not differ significantly between cellular and fibrotic NSIP at 1 and at 3 years (p values > 0.25 for all group comparisons). There was no correlation between BAL neutrophil, eosinophil, or lymphocyte percentages and changes in FVC or DlCO over the next 3 years. Fifty-one of 57 patients followed for a minimum of 3 years after biopsy were treated (prednisolone alone [n = 13], prednisolone in combination with cyclophosphamide [n = 25] or azathioprine [n = 10], azathioprine alone [n = 2], or cyclophosphamide alone [n = 1]). No significant group differences in survival or serial PFT trends were disclosed after exclusion of the six untreated patients.

When pulmonary function trends were evaluated using proportional hazards analysis, changes in FVC at 1 and 3 years, and changes in DlCO at 1 year, were not predictive of survival. However, changes in DlCO at 3 years were linked to survival, both from the date of initial PFT (p = 0.002) and from the date of follow-up PFT at 3 years (p = 0.003) (Figure 5)

; improvements in DlCO were associated with longer survival and declines in DlCO were associated with increased mortality. These findings remained statistically significant, after controlling for initial FVC and DlCO levels and BAL eosinophil levels.

In this study, we describe the histopathologic subsets of FASSc in a large series of patients. The most interesting finding was the high prevalence of NSIP. Histologic subsets have been described in association with dermatomyositis (25, 26) and rheumatoid arthritis (27), but have not been well characterized in pulmonary fibrosis associated with systemic sclerosis. In terms of the histologic pattern of NSIP, the series of Katzenstein and Fiorelli had connective-tissue diseases in only 10 of 64 patients (16%), including patients with rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, polymyositis, and Sjogren's syndrome (15). By contrast, the prevalence of NSIP in idiopathic interstitial pneumonia is now well documented. Bjoraker and coworkers (10) in a retrospective analysis of 104 patients with a previous diagnosis of IPF found that only 14% had NSIP compared with 62% with UIP. However, Nagai and colleagues (13) found that 31 of 111 patients (28%) presenting with idiopathic interstitial lung disease had NSIP, although many patients had the radiographic features of organizing pneumonia, rather than IPF. Recently, NSIP was identified by Travis and coworkers (11) in 29% of patients with idiopathic interstitial lung disease and by Nicholson and colleagues (12) in 35% of patients presenting with cryptogenic fibrosing alveolitis. Thus, NSIP appears to be substantially more prevalent in systemic sclerosis than in idiopathic disease.

The problem of selection bias is common to all histopathologic series of patients with interstitial lung disease. Specifically, it was theoretically possible that in the present series, the performance of lung biopsy might have been reserved for patients with atypical CT findings, leading to an overestimation of the frequency of NSIP. However, it is unlikely that this was a major factor because the prevalence of NSIP was virtually identical before and after December 1990. The distinction between typical and atypical UIP appearances using CT was not made in our unit before 1991 and was not made with confidence until several years later. Broadly, it was unit policy to biopsy patients when possible, if they were considered to have “significant interstitial lung disease,” based on symptoms and pulmonary function indices. The largest groups of patients excluded were those with no evidence of lung involvement and a larger subgroup who were considered to have trivial or minor pulmonary fibrosis, this conclusion being reached on a patient-by-patient basis. Although patients too compromised to undergo biopsy (including those with severe pulmonary vascular disease) and others who declined biopsy were necessarily excluded, these amounted to small subgroups. The authors were not aware of basing the decision to biopsy on atypical as opposed to typical radiologic appearances, although minor bias cannot be wholly excluded.

Our findings differ from those in idiopathic interstitial pneumonia in one further respect. Idiopathic NSIP has a better survival than idiopathic UIP (912), although differences in outcome were more marked in earlier series (9, 10) than in recent reports (11, 12). In the present study survival did not differ significantly between NSIP and UIP/ESL, with both subgroups having a relatively good outcome (5-year survival exceeding 80%) compared with that documented in idiopathic UIP. However, this observation must be interpreted with great caution. Even with the inclusion of six patients with ESL, there were only 12 patients in the UIP/ESL subgroup. ESL has not been classified separately in previous studies of IPF; however, although appearances of ESL are closer to UIP than to NSIP, it is not known whether survival in ESL and UIP are equivalent. It is also possible that “lead time bias” (due to earlier evaluation than in idiopathic disease, due to the presence of systemic disease) obscured differences in outcome between UIP/ESL and NSIP. However, the functional severity of disease was adjusted for in analysis and mean DlCO levels at presentation in UIP patients in the present study (41.8% predicted) were virtually identical to those previously reported at presentation in idiopathic UIP patients at our institution (43.5% predicted) (12).

A further problem is the difficulty in identifying the contribution made by interstitial lung disease to overall mortality. The development of lung cancer may be ascribable to pulmonary fibrosis; patients with systemic sclerosis are known to have an increased risk of cancer (2830), in contrast to patients with idiopathic NSIP, in which a malignant predisposition has yet to be reported. Genetic abnormalities at the level of microsatellite DNA have been found in BAL specimens of patients with FASSc (31). Loss of pulmonary reserve due to interstitial lung disease may contribute to mortality from pulmonary vascular and cardiac disease. In addition, if advanced pulmonary fibrosis is associated with more severe systemic disease, the severity of lung disease may be a marker of nonrespiratory mortality. For all these reasons, analyses of outcome must consist of analyses of overall mortality, as in studies of IPF, rather than mortality primarily due to progression of respiratory disease, although this may obscure prognostic distinctions between UIP and NSIP.

Thus, the finding that mortality in NSIP did not differ from UIP or from UIP/ESL in the present study must be viewed as inconclusive, pending further large histopathologic studies. The more impressive finding was the lack of major decline in serial pulmonary function tests over a 3-year period after presentation in patients with NSIP. It has recently been reported that cyclophosphamide therapy is associated with a substantial reduction in the prevalence of a poor respiratory outcome in systemic sclerosis (32). A number of markers of lung disease were linked to outcome in the present study, both in the whole cohort (DlCO and FVC levels at presentation) and in patients with NSIP (DlCO levels at presentation, BAL eosinophil percentages, and changes in DlCO during the first 3 years of follow-up). However, these findings do not necessarily indicate that the severity and progression of parenchymal lung disease contributed to eventual mortality. Severe depression of DlCO may denote pulmonary vascular disease rather than advanced pulmonary fibrosis. In the present study, 3-year trends in FVC levels had no long-term prognostic significance, suggesting that interstitial lung disease in systemic sclerosis may be arrested or slowed by treatment, and that the link between mortality and DlCO trends might have reflected progression of pulmonary vascular disease.

The observation that increased BAL eosinophil levels were associated with a higher mortality in NSIP is also difficult to interpret. In previous studies of systemic sclerosis (32, 33), a BAL neutrophilia was associated with subsequent declines in pulmonary function tests in untreated patients. In the present study, increases in BAL neutrophil and eosinophil percentages were seen in the majority of patients with NSIP, but were not predictive of subsequent functional trends, despite the previous observation that a BAL neutrophilia is associated with extensive fibrotic disease on HRCT in systemic sclerosis (22). It appears that BAL abnormalities may not identify future progression of pulmonary fibrosis, provided that treatment is instituted. One possible explanation of the link between BAL eosinophil levels and mortality is that a BAL eosinophilia may denote more aggressive systemic disease. Although this speculation is unproven, eosinophilic infiltration is well recognized in systemic sclerosis in extrapulmonary sites (34).

The interobserver agreement between pathologists was higher than in two previous series of idiopathic interstitial pneumonia, classified by the same two pathologists (12, 35), reflecting, in part, increasing concordance of diagnostic criteria after discussion of discrepant observations in earlier studies. However, in the view of the observers the higher kappa coefficient of agreement in the present study also reflected the paucity of biopsies with very severe fibrotic disease. The difficulty in discriminating between UIP and advanced NSIP3 was a major source of observer variation in earlier work (12), reinforcing the designation of a separate category of “end-stage lung.” In previous studies (12, 35), these appearances were categorized as UIP, and were grouped with UIP in the present study for analyses of outcome. However, the classification of end-stage lung disease remains problematic; we agree with the suggestion (7) that a term such as “end-stage lung” or “interstitial fibrosis with honeycomb change” is appropriate.

It is unclear whether some patients with NSIP progress to ESL or even to UIP, as has been suggested, based on the finding in idiopathic disease that NSIP and UIP may be found in different biopsy sites in the same patients (36, 37). Progression from NSIP to UIP might explain the subgroup of patients with idiopathic NSIP with a poor outcome (12), but appears less likely to occur in systemic sclerosis judging from the low prevalence of UIP in the present series. However, progression from NSIP to UIP in a small subset of patients, cannot be wholly excluded; the significantly lower gas transfer levels in UIP patients would be compatible with this possibility.

In conclusion, we have found that the great majority of patients with fibrosing alveolitis associated with systemic sclerosis have a histologic pattern of NSIP rather than UIP, in contrast to patients with idiopathic interstitial pneumonia. However, although a number of markers of lung disease were linked to survival, the histopathologic distinction between cellular and fibrotic NSIP had no prognostic significance, and there was little overall functional decline in treated patients with NSIP in the 3 years after presentation.

The authors thank Dr. Katerina Antoniou for her assistance in data collection.

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36. Flaherty KR, Travis WD, Colby TV, Ooews GB, Kazerooni EA, Gross BH, Jain A, Strawderman RL, Flint A, Lynch JP. Martinez FJ. Histopathologic variability in usual and nonspecific interstitial pneumonias. Am J Respir Crit Care Med 2001;164:1722–1727.
37. Nicholson AG, Wells AU. Nonspecific interstitial pneumonia: Nobody Said It's Perfect. Am J Respir Crit Care Med 2001;164:1553–1554.
Correspondence and requests for reprints should be addressed to Athol Wells, M.D., Interstitial Lung Disease Unit, National Heart and Lung Institute, at Imperial College, Emmanuel Kaye Bld, 1 Manresa Rd., London SW3 6LR, UK. E-mail:

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