title: Impaired carbon monoxide diffusing capacity as a marker of limited systemic sclerosis.
abstract: BACKGROUND
  As impairment of diffusing capacity for carbon monoxide (DLCO) likely reflects underlying pulmonary vasculopathy in limited systemic sclerosis (lSSc), we examined whether DLCO could help to distinguish secondary from idiopathic Raynaud's phenomenon (iRP).
  
  
  METHODS
  We compared pulmonary function test (PFT) results in 145 lSSc patients and 24 age- and sex-matched iRP patients. RP duration at time of PFT was similar in the two groups.
  
  
  RESULTS
  DLCO values were low (<80% of predicted) in 106 (73%) of the 145 lSSc patients, and in 69 (71%) of the 97 patients with early lSSc. Interstitial lung disease (ILD) was found in 10% of lSSc patients. DLCO was significantly lower in lSSc than in iRP (72±15% versus 89±9%, p<0.0001). When evaluated, alveolar capillary membrane conductance (Dm) was markedly lower in lSSc patients without ILD than in iRP patients (45±12% versus 71±2.5%, p=0.003), although capillary blood volume was not different. DLCO was low in 3 iRP patients (12.5%). The sensitivity and specificity of low DLCO values for early lSSc diagnosis in patients with Raynaud's phenomenon were 71% and 87.5%, respectively. Sensitivity was similar to that of anti-centromere-antibodies (75%) and nailfold capillary abnormalities (81%). A DLCO cutoff of <70% had a sensitivity and specificity of 41% and 100%, respectively. In multivariable analysis, age and low DLCO were the only independent predictors of death; the hazard ratio for DLCO ≤50% was 7.9 (95% CI 2.3-26, p=0.0007).
  
  
  CONCLUSIONS
  Isolated DLCO impairment is significantly more frequent in patients with lSSc than in patients with idiopathic iRP. DLCO measurement could be a useful diagnostic tool for lSSc.
authors.affiliation: Service de Médecine Interne, CHU Ambroise Paré, 9 av Charles de Gaulle 92100 Boulogne, France. tradsalim@aol.com
authors.forename: Salim
authors.initials: S
authors.lastname: Trad
authors.forename: Du Le Thi
authors.initials: du LT
authors.lastname: Huong
authors.forename: Camille
authors.initials: C
authors.lastname: Frances
authors.forename: Bertrand
authors.initials: B
authors.lastname: Wechsler
authors.forename: Patrice
authors.initials: P
authors.lastname: Cacoub
authors.forename: Nathalie
authors.initials: N
authors.lastname: Costedoat
authors.forename: Julien
authors.initials: J
authors.lastname: Haroche
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Piette
authors.forename: Thomas
authors.initials: T
authors.lastname: Hanslik
authors.forename: Zahir
authors.initials: Z
authors.lastname: Amoura
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D002248:Carbon Monoxide / Q000378:metabolism*; D003937:Diagnosis, Differential; D004058:Diffusion; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D017563:Lung Diseases, Interstitial / Q000175:diagnosis* / Q000378:metabolism / Q000401:mortality; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011650:Pulmonary Alveoli / Q000098:blood supply / Q000378:metabolism; D011652:Pulmonary Circulation / Q000502:physiology; D011928:Raynaud Disease / Q000175:diagnosis* / Q000378:metabolism / Q000401:mortality; D012129:Respiratory Function Tests / Q000379:methods*; D012189:Retrospective Studies; D012595:Scleroderma, Systemic / Q000175:diagnosis* / Q000378:metabolism / Q000401:mortality; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D015415:Biomarkers; D002248:Carbon Monoxide