Diagnostic testing in a population of symptomatic adults receiving ICS for presumed asthma.

Variability in symptoms and lung function, and a lack of accepted gold standard diagnostics, results in diagnostic uncertainty in asthma. As such, treatment is often commenced without confirmatory testing. We evaluated the accuracy of diagnostic tests as part of a clinical study in symptomatic adults taking inhaled corticosteroids(ICS) empirically. We recruited 100 adults with a clinical diagnosis of asthma & persistent respiratory symptoms despite ICS. Spirometry & type 2 (T2) biomarkers were measured at 4 visits over 12 weeks, while diurnal variation (DVPEF) was measured at home. 54 were diagnosed with asthma, an alternate diagnosis was made in 44, & two withdrew. In the asthma cohort (n=54), 20 patients were diagnosed at visit 1, with a further 18 patients diagnosed during study follow-up. Methacholine challenge testing was diagnostic in the remaining 16. Sensitivity & specificity of various diagnostic tests for asthma in this study are presented in table 1. Table 1. Sensitivity & Specificity analysis of diagnostic tests for asthma in this cohort <table-wrap><object-id>erj;64/suppl_68/PA1216/TB1</object-id><object-id>T1</object-id><object-id>TB1</object-id><table><colgroup><col></col><col></col><col></col><col></col><col></col></colgroup><tbody><tr><td></td><td>Sensitivity</td><td>Specificity</td><td>NPV</td><td>PPV</td></tr><tr><td>FEV1/FVC<70%</td><td>59</td><td>91</td><td>65</td><td>89</td></tr><tr><td>FEV1/FVC<75%</td><td>76</td><td>77</td><td> 72 </td><td>80</td></tr><tr><td>BDR>10%pred</td><td>57</td><td>82</td><td>61</td><td>80</td></tr><tr><td>PBE>0.3</td><td>67</td><td>66</td><td>62</td><td>71</td></tr><tr><td>PBE>0.4</td><td>43</td><td>80</td><td>53</td><td>72</td></tr><tr><td>DVPEF>10%</td><td>67</td><td>52</td><td>56</td><td>63</td></tr><tr><td>DVPEF>15%</td><td>32</td><td>89</td><td>51</td><td>77</td></tr><tr><td>DVPEF>20%</td><td>17</td><td>98</td><td>49</td><td>90</td></tr><tr><td>FeNO>25</td><td>70</td><td>59</td><td>62</td><td>68</td></tr><tr><td>FeNO>40</td><td>56</td><td>80</td><td>59</td><td>77</td></tr><tr><td>FeNO>50</td><td>44</td><td>80</td><td>55</td><td>77</td></tr><tr><td>Any T2 inflammation if FEV1/FVC<075%</td><td>80</td><td>30</td><td>27</td><td>83</td></tr><tr><td>DVPEF >15% if any T2 inflammation present</td><td>27</td><td>96</td><td>42</td><td>92</td></tr><tr><td>FEV1/FVC<75% & FeNO>50</td><td>56</td><td>96</td><td>64</td><td>94</td></tr></tbody></table></table-wrap> In conclusion, both physiological testing and T2 biomarker assessment are useful tests for asthma diagnosis in individuals already receiving ICS. Increased sensitivity and diagnostic accuracy was noted by repeated testing in this population.