Clinical decision rule to predict the presence of interstitial lung disease in systemic sclerosis.
OBJECTIVE
To develop a clinical decision rule to predict the presence of interstitial lung disease (ILD) in systemic sclerosis (SSc; scleroderma) and to estimate the prevalence of SSc-ILD.


METHODS
Patient data were extracted from the Canadian Scleroderma Research Group registry. Three algorithms for the clinical decision rule were considered based on lung auscultation, chest radiography (CXR), and % predicted forced vital capacity (FVC). High-resolution computed tomography (HRCT) scans were used as the gold standard to determine the diagnostic properties of the 3 algorithms. Multiple imputation was used to impute HRCT data when missing, thereby avoiding bias due to differential referral for HRCT.


RESULTS
This study included 1,168 patients. Of the patients with HRCT scans, 65% had evidence of ILD, compared to 26% by physical examination and 22% by CXR. The FVC of those who did not have HRCT was 8.8% greater than those who did (95% confidence interval [95% CI] 6.0-11.6%). Algorithm A, which identified the presence of ILD based on crackles on lung auscultation and/or findings on CXR, had a likelihood ratio of 3.9, compared to 3.2 for Algorithm B (which included patients with FVC <70%) and 2.2 for Algorithm C (which included patients with FVC <80%). The prevalence of ILD in the cohort was estimated to be 52% (95% CI 46-59%).


CONCLUSIONS
We developed a simple clinical decision rule to predict SSc-ILD with good test characteristics. The prevalence of ILD in a large, unselected SSc cohort was estimated to be 52%.
Jewish General Hospital and McGill University, Montreal, Quebec, Canada.
Russell
R
Steele
Marie
M
Hudson
Ernest
E
Lo
Murray
M
Baron
D000328:Adult; D000368:Aged; D000465:Algorithms; D002170:Canada; D015331:Cohort Studies; D003661:Decision Support Techniques; D005260:Female; D006801:Humans; D017563:Lung Diseases, Interstitial / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015995:Prevalence; D013902:Radiography, Thoracic; D012135:Respiratory Sounds / Q000502:physiology; D012189:Retrospective Studies; D012595:Scleroderma, Systemic / Q000150:complications*; D014057:Tomography, X-Ray Computed; D014797:Vital Capacity / Q000502:physiology