title: Results of a Prospective Study Evaluating a Noninvasive Method of Hemoglobin Adjustment for Determining the Diffusing Capacity of the Lung.
abstract: BACKGROUND
  Measurement of the diffusing capacity of the lung for carbon monoxide (DlCO) is significantly influenced by the pulmonary capillary blood volume. Consequently, measurements require adjustment for blood hemoglobin concentration (DlCOadj) to allow meaningful clinical interpretation. Noninvasive point-of-care devices that measure hemoglobin transcutaneously provide immediate values for hemoglobin that may be useful in pulmonary function laboratories for determining DlCOadj.
  
  
  OBJECTIVE
  To test the hypothesis that DlCOadjdeterminations obtained with a commercially available device for noninvasive, point-of-care measurement of blood hemoglobin concentrations are not significantly different from determinations obtained using hemoglobin concentrations measured conventionally in venous blood samples.
  
  
  METHODS
  In a prospective open trial, hemoglobin measurements were obtained with the Pronto-7 spot check pulse CO-oximeter (Massimo, Irvine, CA) and by venipuncture for 205 patients referred for DlCOtesting at Cincinnati Children's Hospital. Hemoglobin and DlCOadjmeasurements were compared between the two methods, using Student paired t tests and Bland-Altman plots. To assess variability, the differences in DlCOadjbetween the two methods were also compared by a modification of the current standard for acceptable within-session variability for DlCO. Clinical interpretation for individual DlCOtests based on DlCOadjvalues obtained from the two methods were compared statistically using Kendall's coefficient of concordance to determine whether the Pronto-7 altered the classification of the severity of DlCOdefects.
  
  
  RESULTS
  Measurements of hemoglobin concentration by the Pronto-7 analyzer were significantly lower than those obtained from venipuncture blood samples (13.1 ± 1.8 vs. 13.4 ± 2.0; P = 0.01). However, there were no differences for DlCOadjbetween both methods (23.6 ± 7.7 vs. 23.7 ± 7.5 ml/min/mm Hg; P = 0.42). There was strong correlation between the Pronto-7 and venipuncture DlCOadjvalues (r = 0.99, P < 0.0001). Variability between the two methods was low for DlCOadj, with a bias of -0.07. More than 96% of tests met acceptable within-session variability. There was no significant difference in the clinical interpretation of the DlCOtest based on DlCOadjvalues recovered from both methods (Kendall's coefficient, 0.96).
  
  
  CONCLUSIONS
  Noninvasive measurement of hemoglobin for determination of DlCOadjwas accurate and provided acceptable within-session variability. The results obtained noninvasively did not alter clinical interpretation of test results compared with venipuncture. These findings support noninvasive point-of-care devices as an alternative to venipuncture for determining hemoglobin to measure DlCOadjin most patients.
authors.affiliation: 1 Division of Pulmonary Medicine and.
authors.forename: Karla E
authors.initials: KE
authors.lastname: Foster
authors.affiliation: 2 Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
authors.forename: Rashmi D
authors.initials: RD
authors.lastname: Sahay
authors.affiliation: 2 Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
authors.forename: Nanhua
authors.initials: N
authors.lastname: Zhang
authors.affiliation: 1 Division of Pulmonary Medicine and.
authors.forename: William D
authors.identifier: http://orcid.org/0000-0001-9489-9157
authors.initials: WD
authors.lastname: Hardie
mesh_terms: D000293:Adolescent; D000328:Adult; D002248:Carbon Monoxide; D002648:Child; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D000067716:Point-of-Care Testing; D011446:Prospective Studies; D011653:Pulmonary Diffusing Capacity; D012129:Respiratory Function Tests; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D002248:Carbon Monoxide
keywords: diffusion; point-of-care systems; pulmonary function test