Background
Methods
Study design, setting and participants
Sputum induction and analysis
Asthma phenotypes
Statistical analysis
Results
Subject characteristics
Eosinophilic asthma | Neutrophilic asthma | Mixed granulocytic asthma | Paucigranulocytic asthma | Healthy subjects |
p value | |
---|---|---|---|---|---|---|
N (% of asthmatics) | 350 (42) | 134 (16) | 31 (4) | 318 (38) | 194 | - |
Women, N (%) | 184 (53) | 95 (71)‡†
| 19 (61) | 197 (62) | 105 (54) | 0.002 |
Age, years | 49 (34–60)*
| 52 (41–61)‡*
| 61 (43–71)‡*
| 43 (30–54) | 45 (27–56) | 0.0001 |
BMI | 25.9 ± 4.9‡
| 25.3 ± 5.4 | 25.5 ± 4.6 | 26.1 ± 4.8‡
| 24.3 ± 4.1 | 0.0004 |
Atopy, N (%) | 213 (63)‡
| 69 (52)‡
| 17 (57)‡
| 165 (53)‡
| 46 (28) | <0.001 |
Smoking status, N (%) | ||||||
Non-smokers | 190 (54) | 73 (55) | 19 (61) | 162 (52) | 109 (57) | >0.05 |
Current smokers | 64 (18) | 26 (20) | 5 (16) | 76 (24) | 35 (18) | |
Ex-smokers | 96 (27) | 33 (25) | 7 (23) | 75 (24) | 47 (25) | |
FEV1, % predicted | 81.2 ± 20.9‡*
| 81.6 ± 22.0‡*
| 81.6 ± 20.6‡
| 89.2 ± 18.2‡
| 108.0 ± 13.3 | 0.0001 |
FEV1/FVC, % | 70.7 ± 11.1‡*
| 71.7 ± 11.5‡*
| 70.1 ± 10.5‡*
| 76.2 ± 9.0‡
| 82.1 ± 6.5 | 0.0001 |
FENO, ppb | 43 (23–82)*
| 20 (13–33)†§
| 36 (21–75)*
| 16 (12–29) | / | 0.0001 |
ICS therapy, N (%) | 227 (65) | 87 (65) | 18 (58) | 195 (61) | / | >0.05 |
ICS dosea
| 500 (0–1000) | 800 (0–2000) | 800 (0–1600) | 400 (0–1000) | / | >0.05 |
OCS therapy, N (%) | 21 (6) | 9 (7) | 2 (6) | 14 (4) | / | >0.05 |
LABA, N (%) | 209 (60) | 80 (60) | 20 (65) | 181 (57) | / | >0.05 |
LTRA, N (%) | 75 (21) | 37 (28) | 9 (29) | 73 (23) | / | >0.05 |
Theophylline, N (%) | 11 (3) | 7 (5) | 0 (0) | 11 (3) | / | >0.05 |
Sputum cell counts and viability
Eosinophilic asthma | Neutrophilic asthma | Mixed granulocytic asthma | Paucigranulocytic asthma | Healthy subjects |
p value (Kruskal-Wallis test) | |
---|---|---|---|---|---|---|
Sp. eosinophils ≥3 % | Sp. eosinophils <3 % | Sp. eosinophils ≥3 % | Sp. eosinophils <3 % | |||
Sp. neutrophils <76 % | Sp. neutrophils ≥76 % | Sp. neutrophils ≥76 % | Sp. neutrophils <76 % | |||
Total non-squamous cell count (× 106/g) | 1.18 (0.56–2.85)‡*
| 1.84 (0.82–5.52)‡*†
| 4.10 (1.07–12.00)‡*†
| 0.81 (0.40–2.07) | 0.64 (0.37–1.30) | 0.0001 |
Viability (%) | 64 (50–75) | 79 (68–88)‡*†
| 81 (67–86)‡*†
| 64 (48–75) | 67 (53–78) | 0.0001 |
Squamous cells (%) | 13 (5–25)‡*
| 12 (3–28)‡*
| 6 (2–23)‡*
| 18 (8–35) | 18 (10–31) | 0.0001 |
Eosinophils | ||||||
x 103/g | 201 (64–636)‡*
| 3 (0–27)‡†§
| 271 (46–685)‡*
| 3 (0–10)‡
| 0 (0–2) | 0.0001 |
% of non-squamous cells | 17.1 (7.4–38.0)‡*
| 0.2 (0.0–1.0)‡†§
| 5.2 (3.4–8.8)‡*†
| 0.4 (0.0–1.0)‡
| 0.0 (0.0–0.4) | - |
Neutrophils | ||||||
x 103/g | 335 (135–823)‡
| 1504 (707–4728)‡*†
| 3272 (881–10992)‡*†
| 270 (90–795) | 210 (63–563) | 0.0001 |
% of non-squamous cells | 33 (16–50)*
| 87 (82–93)‡*†
| 83 (79–88)‡*†
| 42 (21–58) | 36 (13–63) | - |
Macrophages | ||||||
x 103/g | 288 (144–648) | 169 (52–425)‡*†
| 218 (77–607) | 337 (167–853) | 285 (120–568) | 0.0001 |
% of non-squamous cells | 27 (16–43)‡*
| 9 (4–13)‡*†
| 6 (3–9)‡*†
| 46 (29–61) | 46 (30–67) | 0.0001 |
Lymphocytes | ||||||
x 103/g | 19 (5–52)‡*
| 12 (2–41) | 19 (0–88) | 10 (3–31) | 10 (4–26) | 0.0012 |
% of non-squamous cells | 1.7 (0.6–3.2) | 1.0 (0.3–1.6)‡*†
| 0.6 (0.0–1.8)‡†
| 1.4 (0.5–2.8) | 1.8 (0.8–3.4) | 0.0001 |
Epithelial cells | ||||||
x 103/g | 56 (20–140)‡
| 18 (3–67)‡*†
| 15 (0–106)*†
| 50 (23–115)‡
| 35 (12–86) | 0.0001 |
% of non-squamous cells | 5.0 (2.0–8.6)*
| 1.0 (0.4–2.0)‡*†
| 0.6 (0.2–1.8)‡*†
| 6.0 (2.8–13.0) | 4.8 (2.2–11.8) | 0.0001 |
Blood leukocyte counts and systemic inflammatory markers
Eosinophilic asthma | Neutrophilic asthma | Mixed granulocytic asthma | Paucigranulocytic asthma | Healthy subjectsa
|
p value (Kruskal-Wallis test) | |
---|---|---|---|---|---|---|
Sp. eosinophils ≥3 % | Sp. eosinophils <3 % | Sp. eosinophils ≥3 % | Sp. eosinophils <3 % | |||
Sp. neutrophils <76 % | Sp. neutrophils ≥76 % | Sp. neutrophils ≥76 % | Sp. neutrophils <76 % | |||
Blood leukocytes (x 103/μL) | 7.76 (6.52–8.87)‡
| 7.75 (6.43–10.00)‡
| 8.02 (6.16–10.83)‡
| 7.25 (6.02–8.75)‡
| 6.12 (5.03–7.37) | 0.0001 |
Blood eosinophils | ||||||
/μL | 315 (202–513)‡*
| 129 (79–228)†§
| 289 (216–449)‡*
| 140 (85–227)‡
| 106 (68–172) | 0.0001 |
% | 4.2 (2.8–6.2)‡*
| 1.7 (1.0–3.0)†§
| 3.9 (2.7–5.8)‡*
| 2.0 (1.1–3.0) | 1.8 (1.0–3.0) | 0.0001 |
Blood neutrophils | ||||||
/μL | 4045 (3204–5140)‡
| 4847 (3260–6323)‡*†
| 4207 (2834–6610) | 3971 (3156–5280)‡
| 3416 (2610–4188) | 0.0001 |
% | 54.0 (47.6–60.1)*
| 59.5 (52.5–69.3)*†
| 57.6 (44.4–62.4) | 56.5 (50.3–62.2) | 54.4 (49.6–62.1) | 0.0001 |
Blood monocytes | ||||||
/μL | 515 (396–667)‡*
| 492 (408–656)‡
| 564 (448–775)‡
| 461 (362–608) | 399 (330–550) | 0.0001 |
% | 6.7 (5.1–8.3) | 6.5 (5.4–8.2) | 7.2 (5.6–9.0) | 6.4 (5.1–8.2) | 7.1 (5.7–8.2) | >0.05 |
Blood lymphocytes | ||||||
/μL | 2358 (1918–2809)‡
| 2249 (1765–2807) | 2180 (1887–2869) | 2337 (1894–2904)‡
| 2009 (1611–2386) | 0.0001 |
% | 31.8 (26.0–38.3) | 29.4 (22.5–37.1)‡*
| 29.1 (21.0–38.2) | 32.7 (27.3–38.2) | 33.9 (26.5–37.7) | 0.006 |
Blood basophils | ||||||
/μL | 42 (29–63)‡*
| 35 (23–51)†
| 39 (27–55) | 34 (24–52) | 34 (24–46) | 0.0001 |
% | 0.6 (0.4–0.8)*
| 0.5 (0.3–0.6)‡†
| 0.5 (0.4–0.7) | 0.5 (0.3–0.7) | 0.5 (0.4–0.8) | 0.0001 |
CRP (mg/L)b
| 1.4 (0.6–3.6) | 1.9 (0.8–5.3)‡
| 2.9 (0.6–8.9) | 1.6 (0.6–4.5) | 1.1 (0.4–2.4) | 0.034 |
Fibrinogen (g/L)c
| 3.2 (2.8–3.8)‡
| 3.2 (2.8–3.7)‡
| 3.3 (2.7–3.9) | 3.1 (2.7–3.6) | 2.9 (2.6–3.2) | 0.0008 |
Analysis of asthma phenotypes according to treatment with inhaled corticosteroids (ICS) and comparison with healthy subjects
Paucigranulocytic asthma, not treated with ICS | Paucigranulocytic asthma, treated with ICS | ICS- vs ICS+ | Neutrophilic asthma, not treated with ICS | Neutrophilic asthma, treated with ICS | ICS- vs ICS+ | Healthy subjects | |
---|---|---|---|---|---|---|---|
N | 123 | 195 | - | 47 | 87 | - | 194 |
Sputum total non-squamous cell count (x 106/g) | 0.93 (0.43–2.12) | 0.69 (0.36–1.61) | NS | 1.45 (0.82–4.65)‡
| 2.10 (0.75–8.02)‡
| NS | 0.64 (0.37–1.30) |
Sputum viability (%) | 65 (48–78) | 64 (48–75) | NS | 78 (68–87)‡
| 80 (68–88)‡
| NS | 67 (53–78) |
Sputum squamous cells (%) | 16 (7–30) | 19 (10–37) | NS | 18 (5–30) | 7 (2–27)‡
| NS | 18 (10–31) |
Sputum eosinophils (x 103/g) | 4 (0–15)‡
| 2 (0–10)‡
| NS | 2 (0–28)‡
| 4 (0–27)‡
| NS | 0 (0–2) |
Sputum neutrophils (x 103/g) | 315 (97–994) | 245 (86–710) | NS | 1197 (707–3776)‡
| 1879 (593–7060)‡
| NS | 210 (63–563) |
Sputum macrophages (x 103/g) | 451 (188–864)‡
| 280 (154–853) | NS | 127 (33–396)‡
| 182 (52–436) | NS | 285 (120–568) |
Sputum lymphocytes (x 103/g) | 12 (3–45) | 10 (2–24) | NS | 15 (4–41) | 11 (1–39) | NS | 10 (4–26) |
Sputum epithelial cells (x 103/g) | 48 (19–113) | 52 (25–120)‡
| NS | 19 (4–44) | 18 (3–73) | NS | 35 (12–86) |
Blood leukocytes (x103/μL)a
| 6.87 (5.85–8.51)‡
| 7.47 (6.32–9.06)‡
| NS | 7.87 (6.41–9.93)‡
| 7.71 (6.44–10.06)‡
| NS | 6.12 (5.03–7.37) |
Blood eosinophils (/μL)a
| 145 (101–217)‡
| 139 (74–229) | NS | 172 (63–293) | 123 (80–215) | NS | 106 (68–172) |
Blood neutrophils (/μL)a
| 3598 (2924–5119) | 4211 (3392–5392)‡
| NS | 4804 (3158–6021)‡
| 4885 (3403–6969)‡
| NS | 3416 (2610–4188) |
Blood monocytes (/μL)a
| 461 (353–592) | 463 (370–615)‡
| NS | 476 (387–648) | 519 (419–669)‡
| NS | 399 (330–550) |
Blood lymphocytes (/μL)a
| 2352 (1891–2967)‡
| 2321 (1900–2855)‡
| NS | 2518 (1989–3035)‡
| 2167 (1675–2726) | NS | 2009 (1611–2386) |
Blood basophils (/μL)a
| 35 (25–52) | 33 (24–51) | NS | 40 (29–53) | 33 (22–50) | NS | 34 (24–46) |
Analysis of asthma phenotypes classified with a threshold of sputum eosinophils of 1.01 %
Eosinophilic asthma | Neutrophilic asthma | Mixed granulocytic asthma | Paucigranulocytic asthma | Healthy subjects | p value (Kruskal- Wallis test) | |
---|---|---|---|---|---|---|
Sp. eosinophils ≥1.01 % | Sp. eosinophils <1.01 % | Sp. eosinophils ≥1.01 % | Sp. eosinophils <1.01 % | |||
Sp. neutrophils <76 % | Sp. neutrophils ≥76 % | Sp. neutrophils ≥76 % | Sp. neutrophils <76 % | |||
N (% of asthmatics) | 429 (51) | 106 (13) | 59 (7) | 239 (29) | 194 | - |
Sputum eosinophils | ||||||
x 103/g | 127 (38–471)‡*
| 0 (0–9)†§
| 77 (31–380)‡*
| 0 (0–5)‡‡
| 0 (0–2) | 0.0001 |
% of non-squamous cells | 11.8 (4.0–30.8)‡*
| 0.0 (0.0–0.5)†§
| 3.0 (1.8–6.0)‡*†
| 0.2 (0.0–0.5) | 0.0 (0.0–0.4) | 0.0001 |
Blood eosinophilsa
| ||||||
/μL | 289 (181–444)‡*
| 123 (62–220)†§
| 266 (126–430)‡*
| 133 (78–200) | 106 (68–172) | 0.0001 |
% | 3.8 (2.4–5.6)‡*
| 1.7 (0.9–3.0)†§
| 2.9 (1.8–5.6)‡*
| 1.9 (1.0–2.7) | 1.8 (1.0–3.0) | 0.0001 |
Analysis according to atopy
Non-atopic asthmatics | Atopic asthmatics | Non-atopic healthy subjects | Atopic healthy subjects | p value (Kruskal-Wallis test) | |
---|---|---|---|---|---|
N | 344 | 464 | 118 | 46 | - |
Sputum eosinophils | |||||
x 103/g | 19 (1–173)‡*
| 34 (3–181)‡*
| 0 (0–3) | 0 (0–4) | 0.0001 |
% of non-squamous cells | 1.6 (0.2–9.6)‡*
| 2.8 (0.2–13.8)‡*
| 0.0 (0.0–0.4) | 0.0 (0.0–0.5) | 0.0001 |
Blood eosinophilsa
| |||||
/μL | 188 (109–327)‡
| 217 (124–375)‡*
| 93 (62–135) | 134 (80–202) | 0.0001 |
% | 2.6 (1.4–4.0)‡
| 3.0 (1.7–4.7)‡
| 1.5 (0.9–2.9) | 2.1 (1.6–3.0) | 0.0001 |