LETTERS Reproducibility of a Single Blood Eosinophil Measurement as a Biomarker in Severe Eosinophilic Asthma To the Editor: Recently there has been interest in characterizing eosinophilic inflammation in asthma. Clinical trials of biological agents for the treatment of asthma have explored the use of a single blood eosinophil measurement as an inclusion criterion and potential biomarker to identify patients with severe eosinophilic asthma (1, 2). When using biomarkers, clinical decisions are generally based on whether an individual result is greater than or less than a chosen cut point for the biomarker. Low/normal values are interpreted as indicating the absence of clinically important underlying disease activity (e.g., inflammation). Abnormally high values indicate its presence. However, it is important to know the performance characteristics that apply for a particular cut point and to adjust expectations of the test accordingly. As a result of diurnal and compartment variation (blood vs. tissue), the short half-life of eosinophils, and the sensitivity to external factors (e.g., allergen exposure, corticosteroid use), fluctuations in the blood eosinophil count may occur. Accordingly, we set out to determine the reproducibility of a single blood eosinophil count as a biomarker, using data previously derived from one, and now from a second of two, recently published multicenter clinical trials of mepolizumab treatment for severe eosinophilic asthma. For our post hoc analyses of both clinical trials, we modeled (on the log scale) postscreening blood eosinophil measurements,
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using a repeated measures model with fixed covariates of visit, screening blood eosinophil measurement, and an interaction term for visit by screening measurement. The geometric mean of the modeled postscreening measurements was plotted against the screening value for each subject to examine how well the screening measurement matched the post-screening average. We then examined the use of a single blood eosinophil measure compared with using the average of repeated 4-weekly consecutive eosinophil measurements. We previously reported (3) that in patients who received placebo (N = 115) in the Dose Ranging Efficacy and Safety with Mepolizumab in Severe Asthma (DREAM) study (4) (ClinicalTrials.gov NCT01000506) with eosinophils 150 cells/ml or greater at screening, 85% of patients remained above this level, on average, for post-screening measurements obtained over the subsequent 56 weeks (Figure 1A). Using blood samples from patients with an average of 150 cells/ml or greater from two, three, or four measurements, 85%, 90%, and 92% had a post-screening average eosinophil count above 150 cells/ml, respectively (Figure 2, blue bars). In the present study, we analyzed data derived from the Efficacy and Safety Study of Mepolizumab Adjunctive Therapy in Subjects with Severe Uncontrolled Refractory Asthma (MENSA) study (1) (ClinicalTrials.gov NCT01691521). Here, we report on 188 patients at screening who received placebo and had a blood eosinophil count of 150 cells/ml or greater (167 [89%] of 188 patients). Of the 167 patients, 143 (86%) had an average of 150 cells/ml or greater in the following 8 months (Figure 1B). Using the average of two, three, or four measurements (each taken 4 wk apart), of the patients with an average of 150 cells/ml or greater, 138 (88%), 140 (88%), and 139 (89%), respectively, have averages
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Figure 1. Screening eosinophils versus the geometric mean after screening. (A) Dose Ranging Efficacy and Safety with Mepolizumab in Severe Asthma (DREAM) study. (B) Efficacy and Safety Study of Mepolizumab Adjunctive Therapy in Subjects with Severe Uncontrolled Refractory Asthma (MENSA) study. Predicted geometric mean after screening (blue line). Line of identity (dotted line). The graph is divided into quadrants, with the perpendicular line representing the cell counts that are higher than 150 cells/ml or lower than 150 cells/ml at screening and the horizontal line representing the geometric mean after screening of more than 150 cells/ml or less than 150 cells/ml. A is reprinted by permission from Reference 3.
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LETTERS
% of Patients with Average Blood Eosinophil Threshold ≥150 cells/μL
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DREAM (n=115)
MENSA (n=167)
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and 1.8 (0.3–5.7), respectively. The performance in terms of clinical usefulness for leukocyte differential counts, including eosinophils, was consistent across these platforms. In summary, our current analysis of data derived from the MENSA replicated the observations from our previous analysis of data generated by the DREAM study. This study further supports the utility of a single blood eosinophil measurement of 150 cells/ml or more to identify patients eligible for the treatment of mepolizumab before initiating treatment. Samples with eosinophil counts close to 150 cells/ml at treatment initiation may warrant a repeat blood test a few weeks later to confirm the phenotype. These results could be generalizable to other recommended platforms (6) for measuring blood eosinophils.
0 1 2 3 4 Number of Blood Samples Used to Predict Subsequent Eosinophil Count Average Figure 2. Stability of blood eosinophils in placebo patients. Data from the DREAM study (blue bars) show that in those patients with a blood eosinophil measurement at screening of 150 cells/ml or more, 85% had an average value over the subsequent year above this threshold. Using the average of the two measures from baseline and screening, a similar percentage was observed in subsequent measures. Similarly, using the average of three measurements, there was a small increase, to 90%, and using an average of four measurements resulted in 92%, with an average value of 150 cells/ml or more. There were a total of 14 measurements. Data from the MENSA study (orange bars) show a similar pattern; there were a total of eight measurements. Bars represent mean 6 standard error of the mean. The number of patients with average blood eosinophils of 150 cells/ml or more from one, two, three, and four samples in DREAM was 115, 120, 116, and 118, respectively. In MENSA it was 167, 157, 160, and 156 patients, respectively.
that remained above 150 cells/ml, based on the subsequent visits during the remaining 8-month study period (Figure 2, orange bars). Patients continued receiving their baseline therapy throughout the duration of both studies. In the two studies, the time for collection of the blood samples was not mandated; however, the large majority of the samples was collected in the morning. In both studies, eosinophil counts were measured using the Beckman Coulter LH750 analyzer (Quest Diagnostics Laboratory, Valencia, CA). A recent study (5) using 100 samples from healthy individuals compared the performance of four analyzers, including Beckman Coulter LH 750 (Miami, FL), Abbott CELLDYN Sapphire (Santa Clara, CA), ADVIA 120 (Bayer Diagnostics, Tarrytown, NY), and Sysmex XE-2100 (TOA Medical Electronics Co., Kobe, Japan) in terms of distributional classification, morphologic classification, and morphologic flags. The median (2.5–97.5 percentile) eosinophil counts across these analyzers were comparable, at 2.3 (0.0–6.5), 2.1 (0.6–5.8), 1.9 (0.3–5.1),
Missing Stowaways and Lack of Expected Concurrent Infections To the Editor: We read with great interest the recent article by Interrante and colleagues (1) on the exogenous reinfection etiology of late Letters
Author disclosures are available with the text of this letter at www.atsjournals.org. Hector Ortega, M.D., Sc.D. GlaxoSmithKline Research Triangle Park, North Carolina Gerald Gleich, M.D. University of Utah Health Sciences Center Salt Lake City, Utah Bhabita Mayer, M.Sc. GlaxoSmithKline Stockley Park, United Kingdom Steve Yancey, M.Sc. GlaxoSmithKline Research Triangle Park, North Carolina
References 1 Ortega HG, Liu MC, Pavord ID, Brusselle GG, FitzGerald JM, Chetta A, Humbert M, Katz LE, Keene ON, Yancey SW, et al.; MENSA Investigators. Mepolizumab treatment in patients with severe eosinophilic asthma. N Engl J Med 2014;371:1198–1207. 2 Bel EH, Wenzel SE, Thompson PJ, Prazma CM, Keene ON, Yancey SW, Ortega HG, Pavord ID; SIRIUS Investigators. Oral glucocorticoidsparing effect of mepolizumab in eosinophilic asthma. N Engl J Med 2014;371:1189–1197. 3 Katz LE, Gleich GJ, Hartley BF, Yancey SW, Ortega HG. Blood eosinophil count is a useful biomarker to identify patients with severe eosinophilic asthma. Ann Am Thorac Soc 2014;11:531–536. 4 Pavord ID, Korn S, Howarth P, Bleecker ER, Buhl R, Keene ON, Ortega H, Chanez P. Mepolizumab for severe eosinophilic asthma (DREAM): a multicentre, double-blind, placebo-controlled trial. Lancet 2012; 380:651–659. 5 Kang SH, Kim HK, Ham CK, Lee DS, Cho H-I. Comparison of four hematology analyzers, CELL-DYN Sapphire, ADVIA 120, Coulter LH 750, and Sysmex XE-2100, in terms of clinical usefulness. Int J Lab Hematol 2008;30:480–486. 6 Szefler SJ, Wenzel S, Brown R, Erzurum SC, Fahy JV, Hamilton RG, Hunt JF, Kita H, Liu AH, Panettieri RA Jr, et al. Asthma outcomes: biomarkers. J Allergy Clin Immunol 2012; 129:S9–S23. Copyright © 2015 by the American Thoracic Society
recurrent tuberculosis in the United States. Public health interventions and research are of paramount importance in controlling the disease, and we commend the authors on their work. However, we believe there are microbiological considerations not addressed in their report that could affect their conclusions. Prior data from tuberculosis studies in the United States suggest a prevalence of coinfection with multiple Mycobacterium 1897
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using a repeated measures model with fixed covariates of visit, screening blood eosinophil measurement, and an interaction term for visit by screening measurement. The geometric mean of the modeled postscreening measurements was plotted against the screening value for each subject to examine how well the screening measurement matched the post-screening average. We then examined the use of a single blood eosinophil measure compared with using the average of repeated 4-weekly consecutive eosinophil measurements. We previously reported (3) that in patients who received placebo (N = 115) in the Dose Ranging Efficacy and Safety with Mepolizumab in Severe Asthma (DREAM) study (4) (ClinicalTrials.gov NCT01000506) with eosinophils 150 cells/ml or greater at screening, 85% of patients remained above this level, on average, for post-screening measurements obtained over the subsequent 56 weeks (Figure 1A). Using blood samples from patients with an average of 150 cells/ml or greater from two, three, or four measurements, 85%, 90%, and 92% had a post-screening average eosinophil count above 150 cells/ml, respectively (Figure 2, blue bars). In the present study, we analyzed data derived from the Efficacy and Safety Study of Mepolizumab Adjunctive Therapy in Subjects with Severe Uncontrolled Refractory Asthma (MENSA) study (1) (ClinicalTrials.gov NCT01691521). Here, we report on 188 patients at screening who received placebo and had a blood eosinophil count of 150 cells/ml or greater (167 [89%] of 188 patients). Of the 167 patients, 143 (86%) had an average of 150 cells/ml or greater in the following 8 months (Figure 1B). Using the average of two, three, or four measurements (each taken 4 wk apart), of the patients with an average of 150 cells/ml or greater, 138 (88%), 140 (88%), and 139 (89%), respectively, have averages
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Figure 1. Screening eosinophils versus the geometric mean after screening. (A) Dose Ranging Efficacy and Safety with Mepolizumab in Severe Asthma (DREAM) study. (B) Efficacy and Safety Study of Mepolizumab Adjunctive Therapy in Subjects with Severe Uncontrolled Refractory Asthma (MENSA) study. Predicted geometric mean after screening (blue line). Line of identity (dotted line). The graph is divided into quadrants, with the perpendicular line representing the cell counts that are higher than 150 cells/ml or lower than 150 cells/ml at screening and the horizontal line representing the geometric mean after screening of more than 150 cells/ml or less than 150 cells/ml. A is reprinted by permission from Reference 3.
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AnnalsATS Volume 12 Number 12 | December 2015
LETTERS
% of Patients with Average Blood Eosinophil Threshold ≥150 cells/μL
100
DREAM (n=115)
MENSA (n=167)
90 80 70
85
86
85
88
90
88
92
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60 50 40 30 20 10
and 1.8 (0.3–5.7), respectively. The performance in terms of clinical usefulness for leukocyte differential counts, including eosinophils, was consistent across these platforms. In summary, our current analysis of data derived from the MENSA replicated the observations from our previous analysis of data generated by the DREAM study. This study further supports the utility of a single blood eosinophil measurement of 150 cells/ml or more to identify patients eligible for the treatment of mepolizumab before initiating treatment. Samples with eosinophil counts close to 150 cells/ml at treatment initiation may warrant a repeat blood test a few weeks later to confirm the phenotype. These results could be generalizable to other recommended platforms (6) for measuring blood eosinophils.
0 1 2 3 4 Number of Blood Samples Used to Predict Subsequent Eosinophil Count Average Figure 2. Stability of blood eosinophils in placebo patients. Data from the DREAM study (blue bars) show that in those patients with a blood eosinophil measurement at screening of 150 cells/ml or more, 85% had an average value over the subsequent year above this threshold. Using the average of the two measures from baseline and screening, a similar percentage was observed in subsequent measures. Similarly, using the average of three measurements, there was a small increase, to 90%, and using an average of four measurements resulted in 92%, with an average value of 150 cells/ml or more. There were a total of 14 measurements. Data from the MENSA study (orange bars) show a similar pattern; there were a total of eight measurements. Bars represent mean 6 standard error of the mean. The number of patients with average blood eosinophils of 150 cells/ml or more from one, two, three, and four samples in DREAM was 115, 120, 116, and 118, respectively. In MENSA it was 167, 157, 160, and 156 patients, respectively.
that remained above 150 cells/ml, based on the subsequent visits during the remaining 8-month study period (Figure 2, orange bars). Patients continued receiving their baseline therapy throughout the duration of both studies. In the two studies, the time for collection of the blood samples was not mandated; however, the large majority of the samples was collected in the morning. In both studies, eosinophil counts were measured using the Beckman Coulter LH750 analyzer (Quest Diagnostics Laboratory, Valencia, CA). A recent study (5) using 100 samples from healthy individuals compared the performance of four analyzers, including Beckman Coulter LH 750 (Miami, FL), Abbott CELLDYN Sapphire (Santa Clara, CA), ADVIA 120 (Bayer Diagnostics, Tarrytown, NY), and Sysmex XE-2100 (TOA Medical Electronics Co., Kobe, Japan) in terms of distributional classification, morphologic classification, and morphologic flags. The median (2.5–97.5 percentile) eosinophil counts across these analyzers were comparable, at 2.3 (0.0–6.5), 2.1 (0.6–5.8), 1.9 (0.3–5.1),
Missing Stowaways and Lack of Expected Concurrent Infections To the Editor: We read with great interest the recent article by Interrante and colleagues (1) on the exogenous reinfection etiology of late Letters
Author disclosures are available with the text of this letter at www.atsjournals.org. Hector Ortega, M.D., Sc.D. GlaxoSmithKline Research Triangle Park, North Carolina Gerald Gleich, M.D. University of Utah Health Sciences Center Salt Lake City, Utah Bhabita Mayer, M.Sc. GlaxoSmithKline Stockley Park, United Kingdom Steve Yancey, M.Sc. GlaxoSmithKline Research Triangle Park, North Carolina
References 1 Ortega HG, Liu MC, Pavord ID, Brusselle GG, FitzGerald JM, Chetta A, Humbert M, Katz LE, Keene ON, Yancey SW, et al.; MENSA Investigators. Mepolizumab treatment in patients with severe eosinophilic asthma. N Engl J Med 2014;371:1198–1207. 2 Bel EH, Wenzel SE, Thompson PJ, Prazma CM, Keene ON, Yancey SW, Ortega HG, Pavord ID; SIRIUS Investigators. Oral glucocorticoidsparing effect of mepolizumab in eosinophilic asthma. N Engl J Med 2014;371:1189–1197. 3 Katz LE, Gleich GJ, Hartley BF, Yancey SW, Ortega HG. Blood eosinophil count is a useful biomarker to identify patients with severe eosinophilic asthma. Ann Am Thorac Soc 2014;11:531–536. 4 Pavord ID, Korn S, Howarth P, Bleecker ER, Buhl R, Keene ON, Ortega H, Chanez P. Mepolizumab for severe eosinophilic asthma (DREAM): a multicentre, double-blind, placebo-controlled trial. Lancet 2012; 380:651–659. 5 Kang SH, Kim HK, Ham CK, Lee DS, Cho H-I. Comparison of four hematology analyzers, CELL-DYN Sapphire, ADVIA 120, Coulter LH 750, and Sysmex XE-2100, in terms of clinical usefulness. Int J Lab Hematol 2008;30:480–486. 6 Szefler SJ, Wenzel S, Brown R, Erzurum SC, Fahy JV, Hamilton RG, Hunt JF, Kita H, Liu AH, Panettieri RA Jr, et al. Asthma outcomes: biomarkers. J Allergy Clin Immunol 2012; 129:S9–S23. Copyright © 2015 by the American Thoracic Society
recurrent tuberculosis in the United States. Public health interventions and research are of paramount importance in controlling the disease, and we commend the authors on their work. However, we believe there are microbiological considerations not addressed in their report that could affect their conclusions. Prior data from tuberculosis studies in the United States suggest a prevalence of coinfection with multiple Mycobacterium 1897
