Egyptian Journal of Chest Diseases and Tuberculosis (2016) 65, 681–688

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The Egyptian Society of Chest Diseases and Tuberculosis

Egyptian Journal of Chest Diseases and Tuberculosis

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ORIGINAL ARTICLE

Correlation of high resolution CT patterns with

pulmonary function tests in patients with interstitial

lung diseases

* Corresponding author.

Peer review under responsibility of The Egyptian Society of Chest Diseases and Tuberculosis.

http://dx.doi.org/10.1016/j.ejcdt.2016.01.0140422-7638 � 2016 The Egyptian Society of Chest Diseases and Tuberculosis. Production and hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Khaled Husseina, Lamiaa H. Shaaban

a,*, Ehab Mohamedb

aChest Department, Assiut University Hospital, Assiut, EgyptbDiagnostic Radiology Department, Assiut University Hospital, Assiut, Egypt

Received 23 December 2015; accepted 28 January 2016

Available online 23 April 2016

KEYWORDS

High resolution CT (HRCT);

Interstitial lung diseases

(ILDs);

Pulmonary function

Abstract Background: Interstitial lung diseases (ILDs) refer to a broad category of lung diseases

characterized by exertional dyspnea, different interstitial patterns on high resolution computed

tomography (HRCT), and abnormal pulmonary functions.

The aim of this study: This is to correlate the radiological pattern and extent of involvement of

ILDs with pulmonary function tests and verify the radiological functional relationship.

Patients and methods: This is a prospective descriptive study which was conducted upon 44

patients aged P18 years, who were diagnosed to have interstitial lung diseases (ILDs), all of them

were admitted to Chest Department, Assiut University Hospitals between June 2014 and May 2015.

They were classified into three groups according to the predominant pattern on HRCT: Group I:

Fibrotic pattern including reticular pattern and/or honeycombing, Group II: Ground glass pattern,

Group III: Nodular pattern. Pulmonary function tests including; forced spirometry, total lung

capacity (TLC), residual volume (RV) and diffusing capacity for carbon monoxide (DlCO) also

O2 saturation via pulse oximetry were done for all patients.

Results: In this study 44 patients with ILDs were included, their mean age was 45.7 years, most

of them were male (63.6%) and non smoker (59.1%) with mean SpO2 87.8%. the most frequent

HRCT pattern was the fibrotic one including reticular and honey combing (45.5%) followed by

ground glass pattern (36%) and the least frequent one was the nodular pattern (18.2%). There

was significant positive correlation between TLC and DLCO in fibrotic pattern (P value = 0.000),

while no correlation could be detected between them in the other two patterns. Moreover, there

was a significant positive correlation between DLCO and SpO2 in all different patterns

(P value = 0.000).

Conclusion: HRCT patterns and degree of lung involvement of ILDs correlate with pulmonary func-

tion parameters. Lung volumes are lower in fibrotic lesion regardless the degree of lung involvement,

682 K. Hussein et al.

while DLCO among different patterns were dependent upon the degree of lung involvement.

Restrictive pulmonary dysfunction correlate with gas exchange in fibrotic pattern while in ground

glass one, gas exchange is independent on lung volumes.

� 2016 The Egyptian Society of Chest Diseases and Tuberculosis. Production and hosting by Elsevier B.V.

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-

nd/4.0/).

Introduction

Interstitial lung diseases (ILDs) refer to a broad category of

lung diseases rather than a specific disease entity. These disor-ders are characterized by exertional dyspnea, interstitial pat-terns on high resolution computed tomography (HRCT),and abnormal pulmonary functions with restrictive ventilatory

defect and decreased diffusing capacity for carbon monoxide(DLCO) [1,2].

Recent classification of ILDs recommended the utilization

of four categories: (1) ILDs of a known cause (such as drugs,associated with a collagen vascular disease, environmentalexposure, etc.); (2) granulomatous ILDs (such as sarcoidosis);

(3) rare ILDs with well-defined clinicopathologic features(such as pulmonary histiocytosis-x, lymphangioleiomyomato-sis); and (4) the idiopathic interstitial pneumonias (IIPs) [3].

IIPsare further subdivided into seven subtypes. Of these, themost common patterns are usual interstitial pneumonia(UIP) called idiopathic pulmonary fibrosis (IPF) and nonspeci-fic interstitial pneumonia (NSIP) [4].

The most common HRCT patterns seen in ILDs are the lin-ear/reticular opacities, cystic lesions, ground-glass opacitiesand nodular pattern.

Pulmonary function testing is often used and recom-mended in the management of patients with ILDs [5]. Thepattern of lung function impairments does not allow a speci-

fic diagnosis to be made, but rather enables one to assess theseverity of lung involvement. The pattern and quantitativerelationships of the impairments of lung volumes and DLCOalso allow defining coexisting complication like pulmonary

hypertension [6].A Few studies were conducted to correlate HRCT pattern

with pulmonary functions. Hansell et al. tried to correlate

the pattern and extent of abnormalities on HRCT with pul-monary function tests in subacute and chronic hypersensitivitypneumonitis and concluded that areas of decreased attenua-

tion and mosaic pattern are an important CT finding that cor-related to obstructive functional abnormalities [7]. Also, morerecent studies were conducted to correlate HRCT pattern and

pulmonary function tests in scleroderma [8], and rheumatoidarthritis [9].

The aim of this study is to correlate the radiological patternand extent of involvement of ILDs with pulmonary function

tests and verify the radiological functional relationship.

Patients and methods

This is a prospective descriptive study which was conductedupon 44 patients aged P18 years, who were diagnosedto have interstitial lung diseases (ILDs) with their high

resolution computed tomography (HRCT) of the chest hadone or more of the following patterns: Fibrotic pattern(reticular and/or honeycombing), ground glass pattern, and

nodular pattern. All of them were admitted to ChestDepartment, Assiut University Hospitals between June2014 and May2015.

Exclusion criteria were pregnancy; acute exacerbation ofIPF; consolidation; predominant cystic pattern as lymphangi-oleiomyomatosis and pulmonary langerhans histiocytosis; pri-

mary pulmonary hypertension; diabetes mellitus; and cardiacdisease.

They were classified into three groups according to predom-inant pattern on HRCT:

GroupI: Fibrotic pattern including reticular pattern and/ or honeycombing.

Group II: Ground glass pattern

Group III: Nodular pattern.

Correlation of high resolution CT patterns with pulmonary function tests 683

All enrolled patients were subjected to:

(1) Thorough history taking and physical examination.(2) Chest HRCT: sections of 1.5 mm were acquired at

10-mm intervals in the supine position. Scans were eval-

uated independently by two observers. According to theextent of involvement on HRCT, a modified quantita-tive scale was used [10]. The findings were assigned as

0; normal, 1; Minimal disease (3–4 septal lines), 2; Mild(P5 septal lines, reticulations, subpleural cysts, andground glass opacities), 3; Moderate disease (grade 2

findings and traction bronchiectasis, peri-bronchovascular thickening or tracheal retraction withone-third to two-third lung involvement), or 4; Severe

(grade 2 or 3 findings with more than two-third lunginvolvement).

(3) Pulmonary function tests (PFTs):

(A) Forced Spirometry (D 97723; Zan 300, Ober-

thulba, Germany) to measure FEV1, FVC, andFEV1/FVC.

(B) Measuring total lung capacity (TLC), and residual

volume (RV): using a constant-volume body ple-thysmograph (D 97723; Zan 300, Oberthulba,Germany).

(C) Diffusing capacity for carbon monoxide (DlCO):as measured by the single-breath technique (CE0535; Zan 300, Oberthulba, Germany).PFTs per-

formed and interpreted according to ATS stan-dards [11,12] and the results were expressed as apercentage of normal predicted values [13].

Table 1 Demographic data of 44 studied patients.

Characteristics

Age (years) (mean ± SD) 45.77 ± 11.7

Sex (No & %)

� Male 28 (63.6%)

� Female 16 (36.4%)

Smoking habit (No & %)

� Smoker 18 (40.9%)

� Non smoker 26 (59.1%)

SpO2 (mean ± SD) 87.8 ± 4.6

(4) O2 saturation is measured via pulse oximetry (SpO2).

Statistical analysis

Analysis was performed using the statistical software (SPSSversion 17; SPSS, Inc., Chicago, IL, USA). Data are presented

as mean ± SD for continuous variables or frequency (percent-age) for categorical variables; using v2-test to compare qualita-tive data while two-sampled unpaired t-test for quantitative

data. P value of <0.05 was considered significant. The corre-

lation of parameters with each other was investigated by the

Pearson correlation test.

Results

In this study 44 patients with ILDs were included, their demo-graphic data are illustrated in Table 1 where their mean agewas 45.7 years, and most of them were male (63.6%) and

non smoker (59.1%) with mean SpO2 87.8%. Fig. 1 revealedthat the most frequent HRCT pattern of the studied groupwas the fibrotic one including reticular and honey combing(45.5%) followed by ground glass pattern (36%) and the least

frequent one was the nodular pattern (18.2%).Table 2 shows that fibrotic pattern was significantly more

frequent among smokers while both ground glass and nodular

ones were significantly more frequent among non smokers(P value 0.01). On measuring the degree of lung involvement,it was revealed that severe lung involvement (>75%)

significantly occurred among different HRCT patterns withP value = 0.007 (Table 3).

In 29 patients with severe lung involvement, lung volumesrevealed that FEV1/FVC had no significant difference between

fibrotic and ground glass pattern while it was significantlylower in nodular one in relation to both (P value = 0.000).FVC, TLC and RV were significantly lower in fibrotic pattern.

On the other hand both TLC and RV had no significant differ-ence between ground glass and nodular patterns. With regardto gas exchange parameters, DLCO had no significant differ-

ence between fibrotic and ground glass pattern; however it

Figure 1 HRCT pattern in 44 studied patients.

Table 2 HRCT pattern in relation to smoking status.

Smoker (18) Non smoker (26) P-value

No. % No. %

Fibrotic 14 70.0 6 30.0 .001*

Ground glass 4 25.0 12 75.0

Nodular 0 0. 8 100.0

* Significant values.

Table 3 Degree of lung involvement in relation to different

HRCT pattern.

Severe lung

involvement (29)

Mild to moderate

lung involvement

(15)

P-value

No. % No. %

Fibrotic 12 60 8 40 0.007*

Ground glass 9 56.2 7 43.8

Nodular 8 100 0 0.

* Significant values.

Table 4 Pulmonary function parameters in relation to HRCT pattern in 29 patients with severe lung involvement.

Fibrotic (mean ± SD) Ground glass (mean ± SD) Nodular (mean ± SD) P1 P2 P3

FEV1/FVC 86.50 ± 3.61 89.44 ± 3.90 65.50 ± 2.49 0.063 0.000* 0.000

FVC 41.33 ± 6.88 55.56 ± 7.32 46.38 ± 6.36 0.000* 0.12 0.01*

TLC 41.83 ± 7.47 56.56 ± 7.45 57.88 ± 6.98 0.000* 0.000* 0.71

RV 39.42 ± 6.68 55.67 ± 7.52 58.75 ± 7.73 0.000* 0.000* 0.38

P1 (fibrotic and ground glass), P2 (fibrotic and nodular), P3 (ground glass and nodular).* Significant P-values.

Table 5 Gas exchange parameters in relation to HRCT pattern in 29 patients with severe lung involvement.

Fibrotic (mean ± SD) Ground glass (mean ± SD) Nodular (mean ± SD) P1 P2 P3

DLCO 37.25 ± 4.63 33.89 ± 3.37 47.75 ± 6.36 0.12 0.000* 0.000*

SpO2 85.83 ± 2.58 81.89 ± 2.47 90.88 ± 2.53 0.002* 0.000* 0.00*

P1 (fibrotic and ground glass), P2 (fibrotic and nodular), P3 (ground glass and nodular).* Significant P-values.

Table 6 Pulmonary function parameters in relation to HRCT

pattern in 15 patients with mild to moderate lung involvement.

Fibrotic (mean

± SD)

Ground glass (mean

± SD)

P

value

FEV1/

FVC

86.00 ± 4.89 85.00 ± 2.16 0.627

FVC 50.75 ± 6.23 61.29 ± 4.31 0.002*

TLC 51.25 ± 7.36 64.43 ± 5.38 0.002*

RV 48.50 ± 5.93 62.43 ± 5.381 0.000*

* Significant values.

Table 7 Gas exchange parameters in relation to HRCT

pattern in 15 patients with mild to moderate lung involvement.

Fibrotic (mean

± SD)

Ground glass (mean

± SD)

P

value

DLCO 43.62 ± 4.95 55.1 ± 3.76 0.000*

SpO2 89 ± 2.75 93.71 ± 1.60 0.002*

* Significant values.

684 K. Hussein et al.

Table 8 Correlation between TLC and DLCO among differ-

ent HRCT patterns.

r P-value

Fibrotic 0.991 0.000*

Ground glass 0.359 0.065

Nodular 0.218 0.302

* Significant values.

Figure 2 Correlation between TLC and DLCO in 20 patients with fibrotic pattern.

Figure 3 Correlation between TLC and DLCO in 16 patients with ground glass pattern.

Table 9 Correlation between DLCO and SpO2 among

different HRCT patterns.

r P-value

Fibrotic 0.980 0.000*

Ground glass 0.986 0.000*

Nodular 0.991 0.000*

* Significant values.

Correlation of high resolution CT patterns with pulmonary function tests 685

686 K. Hussein et al.

was significantly lower in both of them than in nodular pattern(P value = 0.000), also SpO2 was significantly higher in nodu-lar pattern than in fibrotic and ground glass ones (P

value = 0.00) as shown in Tables 4 and 5.In 15 patients with mild to moderate lung involvement;

FVC, TLC and RV were significantly lower in fibrotic pattern

(P value = 0.002, 0.002, and 0.000, respectively); also bothDLCO and SpO2 were significantly lower in fibrotic pattern(P value = 0.000, and 0.02, respectively) as shown in Tables

6 and 7.Table 8 revealed that there was significant positive correla-

tion between TLC and DLCO in fibrotic pattern (Pvalue = 0.000) (Fig. 2) while no correlation could be detected

between them in the other two patterns (Fig. 3). Moreover,there was a significant positive correlation between DLCO

Figure 4 Correlation between DLCO and Sp

Figure 5 Correlation between DLCO and SpO2

and SpO2 in all different patterns (P value = 0.000) as shownin Table 9 and Figs. 4–6.

Discussion

Up till now there is a debate in how much correlation occurredbetween radiological patterns and the pulmonary functions of

ILDs patients. Many investigators have attempted to use PFTsto differentiate patterns of ILDs. The identification of a rela-tively raised residual volume in hypersensitivity pneumonitis

compared with IPF was detected, which is believed to berelated to small airway involvement [14]. In addition, differ-ences in gas exchange have been detected in patients with

IPF appearing to have a greater reduction in DlCO in spiteof correction for lung volume [15].

O2 among 20 patients with fibrotic pattern.

among 16 patients with ground glass pattern.

Figure 6 Correlation between DLCO and SpO2 among 8 patients with nodular pattern.

Correlation of high resolution CT patterns with pulmonary function tests 687

In this study, fibrotic lesions including reticular and honey-combing are the most frequent HRCT findings as it repre-

sented in 45.5% of included patients. This is consistent withthe result of J. Biederer and coworkers who studied 53 patientswith ILDs due to rheumatoid arthritis and detected predomi-

nant reticular pattern in 40 of 53 patients [16]. Seventy percentof patients with fibrotic pattern were current smokers and itmay be attributed to IPF, which represent most of the fibrotic

pattern in HRCT, whereas most patients with ground glassand nodular patterns were non-smokers and this may be dueto non specific interstitial pneumonitis that mostly presented

in collagen vascular disease and to extensive allergic alveolitis,respectively. Fibrotic and ground glass patterns exhibitedrestrictive dysfunction (high FEV1/FVC, and low lung vol-umes) and this is due to the affection of alveoli and interstitial

compartments not related to small airways (interlobular andintralobular septal interstitium). On the other hand, nodularpattern is associated with mixed dysfunction (low FEV1/

FVC, and low lung volumes). This is attributed to the presen-tation of centrilobular nodules in subacute hypersensitivitypneumonitis with bronchiolitis plus the affection of centrilob-

ular interstitium resulting in airway obstruction and this isconsistent with the results of a previous study on hypersensitiv-ity pneumonitis [7].

Results of our study revealed that Lung volumes (FVC,TLC, and RV) were significantly lower in fibrotic lesionregardless to the degree of lung involvement. However DLCOamong different patterns were dependent upon the degree of

lung involvement. In severe lung involvement (>75 affection),severe diffusion defect (DLCO < 40%) was observed in bothfibrotic and ground glass lesions, but in mild to moderate lung

involvement (<75% affection), DLCO is significantly lower infibrotic pattern than ground glass pattern which exhibitedmoderate diffusion defect. This is compatible with a study that

demonstrated a significant negative correlation betweenDLCO and the degree of lung involvement [16]. Non specificinterstitial pneumonia with predominant ground glass in scle-roderma exhibited mild to moderate decreased DLCO in cases

of mild to moderate lung involvement which is compatiblewith our study [8]. Thus DLCO correlates better with theextent of disease on HRCT [17–19].

In this study, in mild to moderate lung involvement ofground glass pattern, the lung volumes (FVC, TLC, and

DLCO) were 61.29 ± 4.3, 64.43 ± 5.38, and 55.1 ± 3.76,respectively. These were comparable with an update study [9]

that studied HRCT pattern and pulmonary function tests inrheumatoid arthritis patients with ILDs, and detected thatthe mean values for FVC, TLC, and DLCO were (60.7

± 0.9, 70 ± 10.4, and 59.4 ± 7.2, respectively).Our results revealed a significant positive correlation

between TLC and DLCO in fibrotic pattern, while no correla-

tion could be detected between them in ground glass patternand this is consistent with another study [20] of 14 patientswith fibrotic pattern of idiopathic pulmonary fibrosis, and

the revealed gas transfer was correlated to lung volumes. Themore affected DLCO with less affected lung volumes inground glass pattern is indicative of pulmonary hypertension[21] that coexists with non specific interstitial pneumonia of

collagen vascular diseases.We detected a highly significant correlation of DLCO with

oxygen saturation (SpO2) in different patterns and this is

explained by the occurrence of gas exchange affection with ear-lier DLCO impairment where there was a reduction of DLCOin all patterns regardless to the degree of lung involvement in

all patients.

Conclusion

HRCT patterns and the degree of lung involvement of ILDscorrelate with pulmonary function parameters. Lung volumesare lower in fibrotic lesion regardless degree of lung involve-

ment, while DLCO among different patterns were dependentupon the degree of lung involvement. Restrictive pulmonarydysfunction correlate with gas exchange in fibrotic patternwhile in ground glass one, gas exchange is independent on lung

volumes.

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