TABLE 1

Demographic and clinical characteristics of the YKL-40 clusters in the Yale Center for Asthma and Airways Disease (YCAAD), Severe Asthma Research Programme (SARP) and New York University/Bellevue Asthma Registry (NYUBAR) cohorts

Total cohortCluster 1Cluster 2Cluster 3Cluster 4p-value
Discovery cohort: YCAAD
 Subjects15676 (49)30 (19)20 (13)30 (19)
 Age years49 (37–58)42 (17–52)49 (37–56)52 (44–57)60 (52–65)<0.01
 Female117 (75)70 (92)7 (23)13 (65)27 (90)<0.01
 Ethnicity
  White114 (73)60 (79)24 (80)11 (55)19 (63)0.2
  African-American29 (19)10 (13)6 (20)5 (25)8 (27)
  Other13 (8)6 (8)4 (20)3 (10)
  Hispanic18 (12)6 (8)3 (10)3 (15)6 (20)0.36
 BMI kg·m−228.9 (23.8–35.7)25.1 (22.2–32.0)30.0 (25.7–32.4)31.2 (27.1–37.1)32.9 (29.0–39.7)<0.01
 Age of onset years21 (5–39)16 (5–31)30 (10–40)5 (3–14)42 (25–54)<0.01
 Asthma duration years21 (10–33)18 (12–32)20 (6–29)40 (32–50)16 (7–30)<0.01
 Severe by EPR-363 (40)16 (21)13 (43)16 (80)18 (60)<0.01
 Lifetime hospitalisations for asthma65 (42)22 (29)12 (40)15 (75)16 (53)<0.01
 Hospitalisations for asthma in the past year35 (22)11 (15)6 (20)7 (35)11 (37)0.04
 ACT score17 (11–21)20 (17–23)13 (10–19)15 (9–20)10 (9–17)<0.01
 Pre-bronchodilator FEV1 % pred82 (60–94)91 (85–103)72 (62–85)43 (34–53)72 (53–81)<0.01
 Post-bronchodilator FEV1 % pred86 (71–98)96 (86–108)86 (76–98)51 (39–56)75 (61–86)<0.01
 Post-bronchodilator FEV1/FVC74 (65–81)79 (73–85)70 (64–75)53 (41–66)71 (64–83)<0.01
 Bronchodilator response % pred5 (2–9)4 (2–7)12 (4–20)6 (4–8)5 (1–10)<0.01
 Inhaled corticosteroid use127 (81)55 (72)25 (83)20 (100)27 (90)0.02
 Inhaled corticosteroid dose μg·day–1500 (0–675)320 (0–640)410 (0–830)640 (500–1000)640 (500–1000)<0.01
 Oral or systemic corticosteroids18 (12)3 (4)3 (10)3 (15)9 (30)<0.01
 LABA use103 (66)40 (53)18 (60)19 (95)26 (87)<0.01
 Serum YKL-40 ng·mL−163 (35–108)48 (32–71)50 (33–88)74 (46–108)206 (110–311)<0.01
Validation cohort 1: SARP
 Subjects16784 (50)57 (34)14 (8)12 (7)
 Age years36 (26–47)33 (25–44)35 (25–43)51 (38–59)48 (46–54)<0.01
 Female115 (68)84 (100)19 (33)6 (43)4 (33)<0.01
 Ethnicity
  White119 (71)60 (71)41 (72)11 (79)7 (58)0.56
  African-American41 (25)19 (23)15 (26)2 (14)5 (42)
  Other7 (4)5 (6)1 (2)1 (7)
 BMI kg·m−226.8 (23.5–32.4)26.1 (23.0–29.8)27.0 (24.0–32.8)28.6 (24.4–32.4)31.1 (27.1–33.3)0.17
 Age of onset years10 (4–26)11 (4–22)6 (2–22)5 (1–28)40 (38–46)<0.01
 Asthma duration years19 (9–32)17 (9–29)20 (15–33)33 (29–45)7 (4–11)<0.01
 Lifetime hospitalisations for asthma71 (43)30 (36)24 (42)12 (86)5 (42)0.01
 Pre-bronchodilator FEV1 % pred80 (62–92)88 (80–98)73 (59–88)32 (28–41)58 (49–70)<0.01
 Post-bronchodilator FEV1 % pred92 (79–102)96 (88–106)89 (79–100)44 (40–49)79 (71–98)<0.01
 Bronchodilator response % pred10 (5–16)7 (4–10)15 (12–22)10 (6–14)12 (10–22)<0.01
 Inhaled corticosteroid use73 (44)35 (42)22 (39)7 (50)9 (75)<0.01
 Oral or systemic corticosteroids19 (12)5 (6)5 (9)5 (36)3 (25)<0.01
 LABA use83 (50)37 (44)25 (44)10 (71)11 (92)<0.01
 Serum YKL-40 ng·mL−149 (34–68)43 (33–61)54 (28–69)70 (42–101)67 (50–165)<0.01
Validation cohort 2: NYUBAR
 Subjects341205 (60)97 (28)15 (4)24 (7)
 Age years37 (25–50)34 (24–49)34 (26–43)46 (42–62)54 (48–62)<0.01
 Female242 (71)205 (100)11 (11)9 (60)17 (71)<0.01
 Ethnicity
  White75 (255)76 (159)68 (66)67 (10)83 (20)0.06
  African-American19 (66)20 (40)19 (19)27 (4)13 (3)
  Other6 (21)3 (6)13 (13)6 (1)4 (1)
  Hispanic188 (55)119 (58)47 (49)9 (60)13 (54)0.46
 BMI kg·m−228.0 (24.0–33.0)28.0 (23.0–33.0)27.0 (24.0–32.0)32.0 (27.5–40.0)28.5 (24.0–33.5)0.09
 Age of onset years16 (8–28)18 (10–27)12 (6–22)9 (5–21)45 (39–53)<0.01
 Asthma duration years16 (7–28)15 (6–25)18 (12–29)36 (32–42)8 (3–16)<0.01
 Severe by EPR-3209 (61)121 (59)50 (52)15 (100)23 (96)0.01
 Hospitalisations for asthma in the past year36 (11)14 (7)11 (11)7 (47)4 (17)<0.01
 Pre-bronchodilator FEV1 % pred82 (71–93)86 (76–95)79 (68–89)40 (33–48)67 (55–72)<0.01
 Post-bronchodilator FEV1 % pred87 (76–96)89 (80–99)86 (77–95)48 (45–51)73 (60–76)<0.01
 Bronchodilator response % pred4 (1–7)3 (1–6)5 (2–10)4 (1–9)6 (2–8)<0.01
 Inhaled corticosteroid use191 (56)109 (53)45 (46)15 (100)22 (92)<0.01
 Oral or systemic corticosteroids199 (58)115 (56)51 (53)15 (100)18 (75)<0.01
 LABA use141 (41)85 (42)29 (30)12 (80)15 (63)<0.01
 Serum YKL-40 ng·mL−156 (42–87)52 (40–80)57 (39–86)99 (60–177)103 (61–156)<0.01

Data are presented as n, n (%) or median (interquartile range). BMI: body mass index; EPR-3: Expert Panel Report-3; ACT: Asthma Control Test; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; LABA: long-acting β-agonist.