Lung CT densitometry in systemic sclerosis: correlation with lung function, exercise testing, and quality of life.
BACKGROUND
To ascertain if analysis of lung density histograms in thin-section CT was more reproducible than visual assessment of lung changes in systemic sclerosis (SSc), and if such density histogram parameters as mean lung attenuation (MLA), skewness, and kurtosis could more closely reflect pulmonary function as well as exercise and quality of life impairment.


METHODS
The intraoperator and interoperator reproducibility of visual and densitometric lung CT analysis in 48 SSc patients examined with CT were evaluated by means of weighted kappa statistics. Univariate and multivariate regression analyses were applied to evaluate the relationship of visual and densitometric CT measurements with functional parameters including functional residual capacity (FRC), FVC, FEV(1), diffusion capacity of the lung for carbon monoxide (Dlco), 6-min walking testing (6MWT), and health-related quality of life questionnaire (QLQ) parameters.


RESULTS
The intraoperator and interoperator reproducibility of MLA (intraobserver weighted kappa = 0.97; interobserver weighted kappa = 0.96), skewness (intraobserver weighted kappa = 0.89; interobserver weighted kappa = 0.88), and kurtosis (intraobserver weighted kappa = 0.89; interobserver weighted kappa = 0.88) were higher than those of visual assessment (intraobserver weighted kappa = 0.71; interobserver weighted kappa = 0.69). In univariate analysis, only densitometric measurements were correlated with some exercise and QLQ parameters. In multivariate analysis, MLA (square regression coefficient corrected [R(2)c] = 0.70), skewness (R(2)c = 0.78), and kurtosis (R(2)c = 0.77) were predicted by FRC, FVC, Dlco, 6MWT, and QLQ parameters, while visual assessment was associated only with FRC and FVC (R(2)c = 0.40).


CONCLUSIONS
In SSc, densitometric analysis is more reproducible than visual assessment of lung changes in thin-section CT and more closely correlated to pulmonary function testing, 6MWT, and QLQ. Density histogram parameters may be useful for cross-sectional and longitudinal studies of lung involvement in SSc.
Camiciottoli
Gianna
G
Respiratory Medicine Unit, Department of Critical Care, University of Florence, Florence, Italy. Electronic address: g.camiciottoli@dac.unifi.it.
Orlandi
Ilaria
I
Radiodiagnostic Section, Department of Clinical Physiopathology, University of Florence, Florence, Italy.
Bartolucci
Maurizio
M
Radiodiagnostic Section, Department of Clinical Physiopathology, University of Florence, Florence, Italy.
Meoni
Eleonora
E
Respiratory Medicine Unit, Department of Critical Care, University of Florence, Florence, Italy.
Nacci
Francesca
F
Respiratory Medicine Unit, Department of Critical Care, University of Florence, Florence, Italy.
Diciotti
Stefano
S
Department of Electronics and Telecommunications, University of Florence, Florence, Italy.
Barcaroli
Chiara
C
Radiodiagnostic Section, Department of Clinical Physiopathology, University of Florence, Florence, Italy.
Conforti
Maria Letizia
ML
Rheumatology Unit, Department of Internal Medicine, University of Florence, Florence, Italy.
Pistolesi
Massimo
M
Respiratory Medicine Unit, Department of Critical Care, University of Florence, Florence, Italy.
Matucci-Cerinic
Marco
M
Rheumatology Unit, Department of Internal Medicine, University of Florence, Florence, Italy.
Mascalchi
Mario
M
Radiodiagnostic Section, Department of Clinical Physiopathology, University of Florence, Florence, Italy.
D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D005080:Exercise Test; D005260:Female; D006801:Humans; D008168:Lung / Q000473:pathology; D017563:Lung Diseases, Interstitial / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010147:Pain Measurement; D011379:Prognosis; D011658:Pulmonary Fibrosis / Q000473:pathology* / Q000503:physiopathology; D011788:Quality of Life; D012044:Regression Analysis; D012129:Respiratory Function Tests; D012595:Scleroderma, Systemic / Q000473:pathology* / Q000503:physiopathology; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed