Background
Methods
Study population and ethics
Pulmonary function procedures
Assessment of airway mechanics
The aerosol provocation system (APS)
Methacholine challenge test (MCT)
Data analysis and statistical methods
Results
Patient characteristics
Asthmatic patients n = 337 | Non-asthmatic subjects
n = 147 | |||||
---|---|---|---|---|---|---|
Upper airway Cough syndrome (UACS) | Gastrooesophageal reflux disease (GERD) | Chronic Cough (smoking, post-infection, unknown) | Symptom complex (dyspnea, chest tightness, hyperventilation, somatisation) | All non-asthmatic subjects | ||
n (% distribution) | 337 (69.6) | 55 (37.4) | 40 (27.2) | 30 (20.4) | 22 (15.0) | 147 (30.4) |
Gender male/female (% distribution) | 129/208 (38.3/61.7) | 26/29 (47.3/52.7) | 18/22 (45.0/55.0) | 18/12 (60.0/40.0) | 8/14 (36.4/63.6) | 70/77 (47.6/52.4) |
Age in years (mean ± SD) (age-range) | 41.3 ± 18.9 (9.1-87.1) | 47.0 ± 17.0 (10.6-80.5) | 55.0 ± 15.3 (26.3-83.1) | 55.2 ± 17.3 (15.9-82.8) | 40.4 ± 18.4 (13.9-72.9) | 49.9 ± 17.5 (10.6-82.8) |
Functional Characteristics of plethysmographic measurements assessed by z-scores n (% within group) | ||||||
Normal LF | 280 (83.1) | 42 (76.4) | 31 (77.5) | 26 (86.7) | 19 (86.4) | 118 (80.3) |
Pulmonary hyperinflation (PHI) | 28 (8.3) | 12 (21.8) | 7 (17.5) | 2 (6.7) | 3 (13.6) | 24 (16.3) |
Bronchial obstruction (O) | 26 (7.7) | 1 (1.8) | 2 (5.0) | 0 | 0 | 3 (2.0) |
PHI and O | 3 (0.9) | 0 | 0 | 2 (6.7) | 0 | 2 (1.4) |
Functional Characteristics of spirometric measurements assessed by z-scores by plethysmography n (%) | ||||||
Normal F-V curve | 305 (90.5) | 50 (36.9) | 40 (100) | 29 (96.7) | 19 (86.4) | 138 (93.9) |
Flow limitation (FL) | 26 (7.7) | 5 (9.1) | 0 | 1 (3.3) | 3 (13.6) | 9 (6.1) |
SAD | 1 (0.3) | 0 | 0 | 0 | 0 | 0 (0) |
FL & SAD | 5 (1.53) | 0 | 0 | 0 | 0 | 0 |
Dose–response curves obtained by using different lung function parameters
Diagnostic accuracy of assessing AHR by using different lung function parameters
PD-40sGeff
| PD-45sGeff
| PD-50sGeff
| PD-20FEV1
| PD-20FEF50
| |
---|---|---|---|---|---|
N | 484 | 484 | 484 | 484 | 484 |
PD-level not reached (%) | 0 (0) | 6 (1.2) | 16 (3.3) | 44 (9.1) | 31 (6.4) |
Diagnostic accuracy differentiating AHR from non-AHR in all patients but excluding patients not having reached PD-level | |||||
n (%) | 484 (100) | 478 (98.8) | 468 (96.7) | 440 (90.9) | 453 (93.6) |
Prevalence | 69.6% | 69.6% | 69.6% | 69.6% | 69.6% |
Sensitivity | 93.2% | 89.3% | 82.8% | 54.9% | 71.5% |
Specificity | 35.4% | 44.2% | 52.4% | 85.0% | 55.1% |
PPV | 76.8% | 78.6% | 79.9% | 89.4% | 78.5% |
NPV | 69.3% | 64.4% | 57.0% | 45.1% | 45.8% |
Diag. Odds Ratio (DOR) [33] | 7.473 | 6.628 | 5.291 | 6.915 | 3.081 |
95% CI of DOR | 4.347–12.847 | 4.123–10.655 | 3.443–8.133 | 4.189–11.417 | 2.061–4.605 |
pos. LR | 1.443 | 1.600 | 1.739 | 3.660 | 1.592 |
neg. LR | 0.192 | 0.242 | 0.328 | 0.531 | 0.517 |
Diagnostic effectiveness | 0.756 | 0.756 | 0.736 | 0.641 | 0.665 |
Cumulative percent-response in all patients (asthmatics and non-asthmatic subjects) at each provocation level n/n (%) | |||||
1st PD level (%) | 161/484 (42.4) | 126/484 (26.0) | 94/484 (19.4) | 94/484 (9.7) | 99/484 (20.5) |
2nd PD level (%) | 362/484 (74.8) | 326/484 (67.4) | 296/484 (61.2) | 217/484 (44.8) | 280/484 (57.9) |
3rd PD level (%) | 415/484 (85.7) | 395/484 (81.6) | 376/484 (77.7) | 270/484 (55.8) | 344/484 (71.1) |
No AHR detected | 104/484 (21.5) | 132/484 (27.3) | 164/484 (33.9) | 302/484 (62.4) | 206/484 (42.6) |
Test-duration and MCH-doses to achieve PD-levels
Comparison of average test-duration until different PD-levels reached | |||||
Number | Mean | SD | Lower 95%CL | Upper 95%CL | |
PD40 sGeff
| 484 | 14:45 | 05:54 | 14:15 | 15:14 |
PD20 FEV1
| 484 | 17:46 | 05:16 | 17:18 | 18:14 |
PD20 FEF50
| 484 | 16:17 | 05.36 | 15:47 | 16:47 |
Test-duration: sGeff < FEV1; sGeff < FEF50; FEF50 < FEV1 (p<0.001) | |||||
Provocation-doses of methacholine (mg) needed to reach the different PD levels | |||||
PD40 sGeff
| |||||
AHR | 409 | .495 | .491 | .447 | .543 |
No AHR | 75 | 2.185 | .059 | 2.17 | 2.197 |
PD20 FEV1
| |||||
AHR | 176 | .739 | .615 | .647 | .830 |
No AHR | 243 | 2.189 | .044 | 2.183 | 2.194 |
PD-level not reached | 65 | .873 | .450 | .761 | .985 |
PD20 FEF50
| |||||
AHR | 307 | .625 | .588 | .559 | .691 |
No AHR | 146 | 2.188 | .046 | 2.180 | 2.195 |
PD-level not reached | 31 | .936 | .496 | .754 | 1.117 |
Comparison between the 3 test procedures assessed by summary independent sample t-test | |||||
mean diff. | SE |
t
| Significance | ||
PD40 sGeff versus PD20 FEV1
| .244 | .048 | 5.088 |
p<.000 | |
PD40 sGeff versus PD20 FEF50
| .130 | .040 | 3.223 |
p=.001 | |
PD20 FEV1 versus PD20 FEF50
| .114 | .056 | 2.011 |
p=.045 |