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Impact of personal avoidance practices on health care workers sensitized to natural rubber latex
Impact of personal avoidance practices on health care workers sensitized to natural rubber latex Robert G. Hamilton, PhD, D.ABMLI,a and Robert H. Brown, MD, MPHb,c Baltimore, Md
Key words: Natural rubber latex, natural history, skin test, serologic test, glove provocation
Occupational exposure to natural rubber latex (latex)–containing products has contributed to the sensitization of approximately 10% of the American adult health care worker (HCW) population. Current management practice is to encourage avoidance by separating the latexsensitized individual from the latex allergen source. This action is based on the hypothesis that latex-allergic HCWs who continue to work with or around latex allergen sources will maintain or increase their sensitivity and increase their risk for severe systemic reactions. Presumably those who effectively avoid latex allergen exposure should have a reduction in symptoms and a concomitant decrease in objective measures of sensitization (IgE antibody in the blood, skin test sensitivity). Objective data supporting these beliefs are limited.1 We have conducted a longitudinal study to investigate changes in latex-specific IgE antibody levels in the skin and blood of a cohort of latex-sensitized HCWs to document the natural history of latex allergy after avoidance practice education.
METHODS Twenty anesthesiologists were recruited from among 168 members of the Department of Anesthesiology and Critical Care Medicine at the Johns Hopkins Medical Institutions who had been evaluated in June 1997 for latex sensitization as part of a prevalence study.2 The inclusion criterion was evidence of sensitization to latex with a positive IgE antilatex serologic test or puncture skin test (PST). At 0, 10
From the aDivision of Allergy and Clinical Immunology and the bDepartment of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, and the cEnvironmental Health Sciences/Division of Physiology, Johns Hopkins University School of Public Health, Baltimore, Md. Supported by internal institutional funds. R. G. H. and Johns Hopkins University are entitled to royalties derived from sale of latex skin testing reagents prepared by Greer Laboratories, Inc, used in this study. The terms of this arrangement have been reviewed and approved by Johns Hopkins University in accordance with its conflict-ofinterest policy. Received for publication Oct 26, 1999; revised Dec 17, 1999; accepted for publication Dec 21, 1999. Reprint requests: Robert G. Hamilton, PhD, Johns Hopkins Asthma and Allergy Center, Room 1A20, 5501 Hopkins Bayview Circle, Baltimore, MD 21224. J Allergy Clin Immunol 2000;105:839-41. Copyright © 2000 by Mosby, Inc. 0091-6749/2000 $12.00 + 0 1/54/105224 doi: 10.1067/mai.2000.105224
Abbreviations used HCW: Health care worker Latex: Natural rubber latex PST: Puncture skin test
(n = 20), and 15 (n = 13) months, each subject provided informed consent and a clinical history that documented any changes in the general atopic and latex allergy history status. Each subject provided whole blood by venipuncture and underwent a PST with nonammoniated latex (protein = 0.001, 0.1 and 1 mg/mL, Greer Laboratories, Lenoir, NC). The PST technique was performed with a bifurcated needle according to the multicenter skin testing study protocol.3 Skin testing was not performed in 2 individuals (S. P. and N. F.) who were receiving long-term antihistamines throughout the course of the study. Total serum IgE was measured by the IMx (Abbott Laboratories, Abbott Park, Ill) and multiallergen screen (Phadiatop) and latexspecific IgE was measured in serum with the CAP System (Pharmacia & UpJohn, Kalamazoo, Mich).4 An additional standard dilution was analyzed in all CAP System calibration curves to achieve an analytic sensitivity of 0.17 kIUa/L. An IgE antilatex quality control serum was analyzed in each CAP System assay. It demonstrated an interassay coefficient of variation of 10.4% (0.816 ± 0.085 kIUa/L, n = 46 assays) for latex-specific IgE measurements. To minimize interassay variation, sera collected at different time points from a given patient were reanalyzed in the same assay. At the beginning of this study, all 20 sensitized subjects were advised to avoid latex allergen exposure and were provided synthetic (vinyl or nitrile) gloves. Moreover, the Johns Hopkins Hospital replaced all powdered and powder-free latex examination gloves with vinyl and nitrile gloves systemwide by 8 months after the initial evaluation. Despite personal avoidance of powdered latex gloves, participants worked in operating rooms where powdered surgeon gloves (Triflex, Allegiance, Valencia, Calif) were still used. Initial and final IgE antilatex and PST end-point titer data were analyzed by a paired sign test. Significance was considered to be P < .05.
RESULTS The latex-sensitized study group included 14 male and 6 female anesthesiologists (age range 29 to 54 years). Four anesthesiologists had overt clinical ocular, upper or lower respiratory, or cardiovascular symptoms at the beginning of the study, which they associated with latex glove use (Table I). Eight subjects had initial evidence of localized skin symptoms such as recurrent pruritus and rashes confined to the area of glove contact, and the remaining 8 subjects were asymptomatic. After switching to synthetic gloves, the 4 subjects with initial systemic symptoms and the 8 subjects with localized symptoms all became and remained asymptomatic during the follow-up period. 839
840 Hamilton and Brown
J ALLERGY CLIN IMMUNOL APRIL 2000
TABLE I. Changes in latex-specific IgE antibodies in the blood and skin
Subject
Time interval (mo)
S. P.* M. M.† L. L.† L. M.† F. S. R. Z.† L. H. W. B. E. Mo.‡ E. M. S. B.† D. S.† T. T. G. L.§ L. D.§ R. C. S. N.† A. M. S. Pa. N. F†
15 15 15 15 15 15 15 15 15 15 10 10 10 10 10 10 10 15 15 15
IgE antilatex T = 0 (pre) (kIUa/L)
0.85 0.53 0.76 0.41 0.43 <0.17 1.42 1.17 6.66 0.79 <0.17 <0.17 <0.17 1.17 2.28 5.10 0.35 0.73 7.5 4.3
IgE antilatex post (kIUa/L)
<0.17 0.17 0.18 0.20 <0.17 <0.17 0.83 1.05 7.56 0.59 <0.17 <0.17 <0.17 1.07 1.40 4.50 0.50 0.67 5.4 3.1
PST T = 0 (pre) end point titer
PST post end point titer
Relative indicator of skin sensitivity
1 µg/mL 100 µg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL Negative 100 µg/mL 100 µg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL Negative NT NT
100 µg/mL 1 mg/mL Negative Negative Negative Negative Negative 100 µg/mL 100 µg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL 100 µg/mL 100 µg/mL 100 µg/mL 1 mg/mL NT NT
D D D D D D NC NC NC NC NC NC NC NC I I I I NT NT
Data are presented for results obtained at T = 0 and at the last observation (either 10 or 15 months). The end-point titer is the lowest concentration of latex allergen used in PST that produced a positive wheal and erythema. D, Decrease in skin sensitization as measured by a 10-fold or greater increase in the endpoint PST titer; NC, no change in skin sensitization as measured by end-point titer; I, increase in skin sensitization as measured by a 10-fold or greater decrease in end-point PST titer. NT, Subjects receiving long-term antihistamine medications could not be skin tested. *Skin rash, pruritus, rhinoconjunctivitis, and asthma associated with powdered latex glove use. †Evidence of delayed skin symptoms confined to the area of rubber contact. ‡Skin rash, pruritus, rhinoconjunctivitis, asthma, and anaphylaxis associated with powdered latex glove use. §Skin rash/pruritus and conjunctivitis associated with powdered latex glove use.
Forty percent of the study population had an initial history of food allergy, with specific concerns about bananas, avocados, and/or kiwis. The group’s total serum IgE ranged from 27 to 3309 ng/mL and all study subjects were atopic on the basis of a positive multiallergen screen. Table I summarizes the measured changes in latex-specific IgE antibodies in the blood and skin of the study subjects after 10 to 15 months of observation. Of the 16 individuals who initially had a positive serologic test, 14 (88%) showed a decrease in the detectable level of serum latex-specific IgE (P = .01). In the 18 individuals who were skin tested, 6 (33%) showed a decrease and 8 (45%) had no measurable change and 4 (22%) had an increase in their skin reactivity as assessed by PST end-point titration (P > .05).
DISCUSSION Of the 168 anesthesiologists originally evaluated,2 20 subjects with evidence of latex-specific IgE in skin and/or blood were enrolled in this longitudinal study. All subjects had serologic and/or skin test evidence for latex sensitization and at least 2 other known risk factors for latex allergy (powdered latex glove exposure, latex glove–associated hand dermatitis, atopy, or food allergy). Despite evidence of sensitization, 80% were asymptomatic for type 1 hypersensitivity (Table I). We chose to study anesthesiologists because they have daily occupa-
tional skin and inhalation exposure to latex allergen. Swanson et al5 showed that latex aeroallergen levels in surgical suites (111 ± 25 ng/m3) were among the highest in hospital environments and that personal latex aeroallergen exposure of the anesthesiologist (419 ± 292 ng/m3) was among the highest of medical personnel. Air sampling as a means of estimating personal latex aeroallergen exposure was not performed because the 20 anesthesiologists worked in different operating room suites each day with presumably continuously varying levels of aeroallergen. Moreover, the major source of their aeroallergen exposure, the powdered latex examination glove, was entirely phased out from use in the hospital over the first 8 months of the study. Allmers et al1 have shown a decrease in latex-specific IgE antibodies in the blood of HCWs who have avoided powdered latex glove use for 12 months. Our results largely support those observations; however, they also indicate that in situations where powdered latex gloves are used in close proximity by other medical staff personal avoidance may be insufficient to reduce sensitization. The fact that all subjects with less than 15 months of avoidance had either no change or an increase in objective measures of their sensitivity suggests that a longer duration of avoidance may be necessary to achieve measurable decreased sensitization. Most important, a decrease in serum antibody or skin test reactivity to latex may indicate a reduction of
J ALLERGY CLIN IMMUNOL VOLUME 105, NUMBER 4
sensitization but not elimination of risk for resensitization on re-exposure. Continued avoidance is therefore needed despite observed changes in IgE antibody levels during periods of avoidance. REFERENCES 1. Allmers H, Brehler R, Chen Z, Raulf-Heimsoth M, Fels H, Baur X. Reduction of latex aeroallergens and latex-specific IgE antibodies in sensitized workers after removal of powdered natural rubber latex gloves in a hospital. J Allergy Clin Immunol 1998;102:841-6.
Hamilton and Brown 841
2. Brown RH, Schauble JF, Hamilton RG. Prevalence of latex allergy among anesthesiologists: identification of sensitized but asymptomatic individuals. Anesthesiology 1999;90:292-9. 3. Hamilton RG, Adkinson NF Jr, Multi-Center Latex Task Force. Diagnosis of natural rubber latex allergy: multicenter latex skin testing efficacy study. J Allergy Clin Immunol 1998;102:482-90. 4. Hamilton RG, Biagini RE, Krieg EF, Multi-Center Latex Task Force. Diagnostic performance of FDA-cleared serological assays for natural rubber latex specific IgE antibody. J Allergy Clin Immunol 1999;103:925-30. 5. Swanson MC, Bubak ME, Hung LW, Yunginger JW, Warner MA, Reed CE. Quantification of occupational latex aeroallergen in a medical center. J Allergy Clin Immunol 1994;94:445-51.
Correction The following correction applies to the article by Busse et al in the December 1999 issue of the Journal (Busse WW, Brazinsky S, Jacobson K, Stricker W, Schmitt K, Vanden Burgt J, Donnell D, Hannon S, Colice GL. Efficacy response of inhaled beclomethasone dipropionate in asthma is proportional to dose and is improved by formulation with a new propellant. 1999;104:1215-22). Figs 2 and 3 on page 1219 were switched during the publication process. Below are the correct Figs 2 and 3.
FIG 2. The results of the regression analysis for change from baseline in FEV1 percent predicted at week 6 is shown by treatment group. There is a beneficial shift in the dose-response curve for HFA-BDP compared with that for CFC-BDP. This shift is quantified by the relative dose ratio of 2.6, which indicates that it would require 2.6 times the dose of CFC-BDP to achieve the same change in from baseline in FEV1 percent predicted as HFA-BDP; that is, it would require 400 µg/d CFC-BDP to achieve the same effect as 150 µg/d HFA-BDP.
FIG 3. The percent change from baseline in FEF25-75% at week 6 is shown by treatment group. There is a clear trend for improvement in FEF25-75% with increasing doses of HFA-BDP and CFCBDP, along with a beneficial shift in the dose- response curve for HFA-BDP compared with that for CFC-BDP. The values are the means (SE) of the week 6 average.
Key words: Natural rubber latex, natural history, skin test, serologic test, glove provocation
Occupational exposure to natural rubber latex (latex)–containing products has contributed to the sensitization of approximately 10% of the American adult health care worker (HCW) population. Current management practice is to encourage avoidance by separating the latexsensitized individual from the latex allergen source. This action is based on the hypothesis that latex-allergic HCWs who continue to work with or around latex allergen sources will maintain or increase their sensitivity and increase their risk for severe systemic reactions. Presumably those who effectively avoid latex allergen exposure should have a reduction in symptoms and a concomitant decrease in objective measures of sensitization (IgE antibody in the blood, skin test sensitivity). Objective data supporting these beliefs are limited.1 We have conducted a longitudinal study to investigate changes in latex-specific IgE antibody levels in the skin and blood of a cohort of latex-sensitized HCWs to document the natural history of latex allergy after avoidance practice education.
METHODS Twenty anesthesiologists were recruited from among 168 members of the Department of Anesthesiology and Critical Care Medicine at the Johns Hopkins Medical Institutions who had been evaluated in June 1997 for latex sensitization as part of a prevalence study.2 The inclusion criterion was evidence of sensitization to latex with a positive IgE antilatex serologic test or puncture skin test (PST). At 0, 10
From the aDivision of Allergy and Clinical Immunology and the bDepartment of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, and the cEnvironmental Health Sciences/Division of Physiology, Johns Hopkins University School of Public Health, Baltimore, Md. Supported by internal institutional funds. R. G. H. and Johns Hopkins University are entitled to royalties derived from sale of latex skin testing reagents prepared by Greer Laboratories, Inc, used in this study. The terms of this arrangement have been reviewed and approved by Johns Hopkins University in accordance with its conflict-ofinterest policy. Received for publication Oct 26, 1999; revised Dec 17, 1999; accepted for publication Dec 21, 1999. Reprint requests: Robert G. Hamilton, PhD, Johns Hopkins Asthma and Allergy Center, Room 1A20, 5501 Hopkins Bayview Circle, Baltimore, MD 21224. J Allergy Clin Immunol 2000;105:839-41. Copyright © 2000 by Mosby, Inc. 0091-6749/2000 $12.00 + 0 1/54/105224 doi: 10.1067/mai.2000.105224
Abbreviations used HCW: Health care worker Latex: Natural rubber latex PST: Puncture skin test
(n = 20), and 15 (n = 13) months, each subject provided informed consent and a clinical history that documented any changes in the general atopic and latex allergy history status. Each subject provided whole blood by venipuncture and underwent a PST with nonammoniated latex (protein = 0.001, 0.1 and 1 mg/mL, Greer Laboratories, Lenoir, NC). The PST technique was performed with a bifurcated needle according to the multicenter skin testing study protocol.3 Skin testing was not performed in 2 individuals (S. P. and N. F.) who were receiving long-term antihistamines throughout the course of the study. Total serum IgE was measured by the IMx (Abbott Laboratories, Abbott Park, Ill) and multiallergen screen (Phadiatop) and latexspecific IgE was measured in serum with the CAP System (Pharmacia & UpJohn, Kalamazoo, Mich).4 An additional standard dilution was analyzed in all CAP System calibration curves to achieve an analytic sensitivity of 0.17 kIUa/L. An IgE antilatex quality control serum was analyzed in each CAP System assay. It demonstrated an interassay coefficient of variation of 10.4% (0.816 ± 0.085 kIUa/L, n = 46 assays) for latex-specific IgE measurements. To minimize interassay variation, sera collected at different time points from a given patient were reanalyzed in the same assay. At the beginning of this study, all 20 sensitized subjects were advised to avoid latex allergen exposure and were provided synthetic (vinyl or nitrile) gloves. Moreover, the Johns Hopkins Hospital replaced all powdered and powder-free latex examination gloves with vinyl and nitrile gloves systemwide by 8 months after the initial evaluation. Despite personal avoidance of powdered latex gloves, participants worked in operating rooms where powdered surgeon gloves (Triflex, Allegiance, Valencia, Calif) were still used. Initial and final IgE antilatex and PST end-point titer data were analyzed by a paired sign test. Significance was considered to be P < .05.
RESULTS The latex-sensitized study group included 14 male and 6 female anesthesiologists (age range 29 to 54 years). Four anesthesiologists had overt clinical ocular, upper or lower respiratory, or cardiovascular symptoms at the beginning of the study, which they associated with latex glove use (Table I). Eight subjects had initial evidence of localized skin symptoms such as recurrent pruritus and rashes confined to the area of glove contact, and the remaining 8 subjects were asymptomatic. After switching to synthetic gloves, the 4 subjects with initial systemic symptoms and the 8 subjects with localized symptoms all became and remained asymptomatic during the follow-up period. 839
840 Hamilton and Brown
J ALLERGY CLIN IMMUNOL APRIL 2000
TABLE I. Changes in latex-specific IgE antibodies in the blood and skin
Subject
Time interval (mo)
S. P.* M. M.† L. L.† L. M.† F. S. R. Z.† L. H. W. B. E. Mo.‡ E. M. S. B.† D. S.† T. T. G. L.§ L. D.§ R. C. S. N.† A. M. S. Pa. N. F†
15 15 15 15 15 15 15 15 15 15 10 10 10 10 10 10 10 15 15 15
IgE antilatex T = 0 (pre) (kIUa/L)
0.85 0.53 0.76 0.41 0.43 <0.17 1.42 1.17 6.66 0.79 <0.17 <0.17 <0.17 1.17 2.28 5.10 0.35 0.73 7.5 4.3
IgE antilatex post (kIUa/L)
<0.17 0.17 0.18 0.20 <0.17 <0.17 0.83 1.05 7.56 0.59 <0.17 <0.17 <0.17 1.07 1.40 4.50 0.50 0.67 5.4 3.1
PST T = 0 (pre) end point titer
PST post end point titer
Relative indicator of skin sensitivity
1 µg/mL 100 µg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL Negative 100 µg/mL 100 µg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL Negative NT NT
100 µg/mL 1 mg/mL Negative Negative Negative Negative Negative 100 µg/mL 100 µg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL 1 mg/mL 100 µg/mL 100 µg/mL 100 µg/mL 1 mg/mL NT NT
D D D D D D NC NC NC NC NC NC NC NC I I I I NT NT
Data are presented for results obtained at T = 0 and at the last observation (either 10 or 15 months). The end-point titer is the lowest concentration of latex allergen used in PST that produced a positive wheal and erythema. D, Decrease in skin sensitization as measured by a 10-fold or greater increase in the endpoint PST titer; NC, no change in skin sensitization as measured by end-point titer; I, increase in skin sensitization as measured by a 10-fold or greater decrease in end-point PST titer. NT, Subjects receiving long-term antihistamine medications could not be skin tested. *Skin rash, pruritus, rhinoconjunctivitis, and asthma associated with powdered latex glove use. †Evidence of delayed skin symptoms confined to the area of rubber contact. ‡Skin rash, pruritus, rhinoconjunctivitis, asthma, and anaphylaxis associated with powdered latex glove use. §Skin rash/pruritus and conjunctivitis associated with powdered latex glove use.
Forty percent of the study population had an initial history of food allergy, with specific concerns about bananas, avocados, and/or kiwis. The group’s total serum IgE ranged from 27 to 3309 ng/mL and all study subjects were atopic on the basis of a positive multiallergen screen. Table I summarizes the measured changes in latex-specific IgE antibodies in the blood and skin of the study subjects after 10 to 15 months of observation. Of the 16 individuals who initially had a positive serologic test, 14 (88%) showed a decrease in the detectable level of serum latex-specific IgE (P = .01). In the 18 individuals who were skin tested, 6 (33%) showed a decrease and 8 (45%) had no measurable change and 4 (22%) had an increase in their skin reactivity as assessed by PST end-point titration (P > .05).
DISCUSSION Of the 168 anesthesiologists originally evaluated,2 20 subjects with evidence of latex-specific IgE in skin and/or blood were enrolled in this longitudinal study. All subjects had serologic and/or skin test evidence for latex sensitization and at least 2 other known risk factors for latex allergy (powdered latex glove exposure, latex glove–associated hand dermatitis, atopy, or food allergy). Despite evidence of sensitization, 80% were asymptomatic for type 1 hypersensitivity (Table I). We chose to study anesthesiologists because they have daily occupa-
tional skin and inhalation exposure to latex allergen. Swanson et al5 showed that latex aeroallergen levels in surgical suites (111 ± 25 ng/m3) were among the highest in hospital environments and that personal latex aeroallergen exposure of the anesthesiologist (419 ± 292 ng/m3) was among the highest of medical personnel. Air sampling as a means of estimating personal latex aeroallergen exposure was not performed because the 20 anesthesiologists worked in different operating room suites each day with presumably continuously varying levels of aeroallergen. Moreover, the major source of their aeroallergen exposure, the powdered latex examination glove, was entirely phased out from use in the hospital over the first 8 months of the study. Allmers et al1 have shown a decrease in latex-specific IgE antibodies in the blood of HCWs who have avoided powdered latex glove use for 12 months. Our results largely support those observations; however, they also indicate that in situations where powdered latex gloves are used in close proximity by other medical staff personal avoidance may be insufficient to reduce sensitization. The fact that all subjects with less than 15 months of avoidance had either no change or an increase in objective measures of their sensitivity suggests that a longer duration of avoidance may be necessary to achieve measurable decreased sensitization. Most important, a decrease in serum antibody or skin test reactivity to latex may indicate a reduction of
J ALLERGY CLIN IMMUNOL VOLUME 105, NUMBER 4
sensitization but not elimination of risk for resensitization on re-exposure. Continued avoidance is therefore needed despite observed changes in IgE antibody levels during periods of avoidance. REFERENCES 1. Allmers H, Brehler R, Chen Z, Raulf-Heimsoth M, Fels H, Baur X. Reduction of latex aeroallergens and latex-specific IgE antibodies in sensitized workers after removal of powdered natural rubber latex gloves in a hospital. J Allergy Clin Immunol 1998;102:841-6.
Hamilton and Brown 841
2. Brown RH, Schauble JF, Hamilton RG. Prevalence of latex allergy among anesthesiologists: identification of sensitized but asymptomatic individuals. Anesthesiology 1999;90:292-9. 3. Hamilton RG, Adkinson NF Jr, Multi-Center Latex Task Force. Diagnosis of natural rubber latex allergy: multicenter latex skin testing efficacy study. J Allergy Clin Immunol 1998;102:482-90. 4. Hamilton RG, Biagini RE, Krieg EF, Multi-Center Latex Task Force. Diagnostic performance of FDA-cleared serological assays for natural rubber latex specific IgE antibody. J Allergy Clin Immunol 1999;103:925-30. 5. Swanson MC, Bubak ME, Hung LW, Yunginger JW, Warner MA, Reed CE. Quantification of occupational latex aeroallergen in a medical center. J Allergy Clin Immunol 1994;94:445-51.
Correction The following correction applies to the article by Busse et al in the December 1999 issue of the Journal (Busse WW, Brazinsky S, Jacobson K, Stricker W, Schmitt K, Vanden Burgt J, Donnell D, Hannon S, Colice GL. Efficacy response of inhaled beclomethasone dipropionate in asthma is proportional to dose and is improved by formulation with a new propellant. 1999;104:1215-22). Figs 2 and 3 on page 1219 were switched during the publication process. Below are the correct Figs 2 and 3.
FIG 2. The results of the regression analysis for change from baseline in FEV1 percent predicted at week 6 is shown by treatment group. There is a beneficial shift in the dose-response curve for HFA-BDP compared with that for CFC-BDP. This shift is quantified by the relative dose ratio of 2.6, which indicates that it would require 2.6 times the dose of CFC-BDP to achieve the same change in from baseline in FEV1 percent predicted as HFA-BDP; that is, it would require 400 µg/d CFC-BDP to achieve the same effect as 150 µg/d HFA-BDP.
FIG 3. The percent change from baseline in FEF25-75% at week 6 is shown by treatment group. There is a clear trend for improvement in FEF25-75% with increasing doses of HFA-BDP and CFCBDP, along with a beneficial shift in the dose- response curve for HFA-BDP compared with that for CFC-BDP. The values are the means (SE) of the week 6 average.