title: Membrane diffusion- and capillary blood volume measurements are not useful as screening tools for pulmonary arterial hypertension in systemic sclerosis: a case control study.
abstract: BACKGROUND
  There is no optimal screening tool for the assessment of pulmonary arterial hypertension (PAH) in patients with systemic sclerosis (SSc). A decreasing transfer factor of the lung for CO (TLCO) is associated with the development of PAH in SSc. TLCO can be partitioned into the diffusion of the alveolar capillary membrane (Dm) and the capillary blood volume (Vc). The use of the partitioned diffusion to detect PAH in SSc is not well established yet. This study evaluates whether Dm and Vc could be candidates for further study of the use for screening for PAH in SSc.
  
  
  METHODS
  Eleven SSc patients with PAH (SScPAH+), 13 SSc patients without PAH (SScPAH-) and 10 healthy control subjects were included. Pulmonary function testing took place at diagnosis of PAH. TLCO was partitioned according to Roughton and Forster. As pulmonary fibrosis in SSc influences values of the (partitioned) TLCO, these were adjusted for fibrosis score as assessed on HRCT.
  
  
  RESULTS
  TLCO as percentage of predicted (%) was lower in SScPAH+ than in SScPAH- (41 +/- 7% vs. 63 +/- 12%, p < 0.0001, respectively). Dm% in SScPAH+ was decreased as compared with SScPAH- (22 +/- 6% vs. 39 +/- 12%, p < 0.0001, respectively), also after adjustment for total fibrosis score (before adjustment: B = 17.5, 95% CI 9.0-25.9, p = < 0.0001; after adjustment: B = 14.3, 95% CI 6.0-21.7, p = 0.008). No difference was found in Vc%. There were no correlations between pulmonary hemodynamic parameters and Dm% in the PAH groups.
  
  
  CONCLUSIONS
  SScPAH+ patients have lower Dm% than SScPAH- patients. There are no correlations between Dm% and hemodynamic parameters of PAH in SScPAH+. These findings do not support further study of the role of partitioning TLCO in the diagnostic work- up for PAH in SSc.
authors.affiliation: Department of Pulmonary Diseases, VU University Medical Center, Amsterdam, The Netherlands. mj.overbeek@vumc.nl
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Overbeek
authors.forename: Herman
authors.initials: H
authors.lastname: Groepenhoff
authors.forename: Alexandre E
authors.initials: AE
authors.lastname: Voskuyl
authors.forename: Egbert F
authors.initials: EF
authors.lastname: Smit
authors.forename: Jochem W L
authors.initials: JW
authors.lastname: Peeters
authors.forename: Anton
authors.initials: A
authors.lastname: Vonk-Noordegraaf
authors.forename: Marieke D
authors.initials: MD
authors.lastname: Spreeuwenberg
authors.forename: Ben C
authors.initials: BC
authors.lastname: Dijkmans
authors.forename: Anco
authors.initials: A
authors.lastname: Boonstra
mesh_terms: D000368:Aged; D002196:Capillaries / Q000503:physiopathology*; D002245:Carbon Dioxide / Q000378:metabolism; D016022:Case-Control Studies; D002462:Cell Membrane / Q000378:metabolism; D004058:Diffusion; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D008168:Lung / Q000098:blood supply / Q000503:physiopathology*; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D011653:Pulmonary Diffusing Capacity / Q000379:methods*; D015203:Reproducibility of Results; D012595:Scleroderma, Systemic / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D012680:Sensitivity and Specificity
chemical_list: D002245:Carbon Dioxide