Table 1 cross-tabulates responses from the questionnaire with physician claims. The agreement, indicated by kappa coefficients, between physician visits for asthma during one year before the survey and responses to survey questions about asthma attacks and the use of medication was moderate (k=0.45 to 0.50) . Agreement improved substantially if two years of physician contacts were compared with questionnaire data (k=0.60); considering additional years produced little further improvement. The kappa coefficients were similar for asthma attacks and use of medication, and for those reporting either or both of these (Table 1).
Table 1 also shows sensitivity and specificity of the administrative data in identifying those who had had an asthma attack in the previous 12 months or who were taking asthma medication at that time. The poor sensitivity for physician contacts within one year before completing the questionnaire (37.9% for asthma attacks and 41.3% for the use of medication) improved as additional years of physician contacts were considered. Approximately two-thirds of those patients who had suffered from an asthma attack in the previous 12 months or who were taking asthma medication had a record of seeing a physician for asthma within five years before completing the questionnaire. On the other hand, specificity was over 98% for the first year and decreased slightly with time.
Table 1. Agreement between responses to the questionnaire and the database
| Physician contact within | Responses to the questionnaire Asthma attack Use of medication Attack or medication Attack and medication Yes No Yes No Yes No Yes No | Any asthma symptom* Yes No | ||||
| 0-1 years | Yes (n) | 64 36 | 71 29 | 81 19 | 54 46 | 98 2 |
| No (n) | 105 2274 | 101 2278 | 133 2246 | 73 2306 | 1164 1215 | |
| Kappa | 0.45 (0.37-0.52) | 0.50 (0.42-0.57) | 0.49 (0.42-0.56) | 0.45 (0.37-0.53) | 0.08 (0.06-0.09) | |
| Sensitivity (%) | 37.9 | 41.3 | 37.9 | 42.5 | 7.8 | |
| Specificity (%) | 98.4 | 98.7 | 99.2 | 98.0 | 99.8 | |
| 0-2 years | Yes (n) | 86 45 | 93 38 | 107 24 | 72 59 | 127 4 |
| No (n) | 83 2265 | 79 2269 | 107 2241 | 55 2293 | 1135 1213 | |
| Kappa | 0.55 (0.48-0.62) | 0.59 (0.52-0.66) | 0.59 (0.53-0.66) | 0.53 (0.46-0.61) | 0.10 (0.08-0.11) | |
| Sensitivity (%) | 50.9 | 54.1 | 50.0 | 56.7 | 10.1 | |
| Specificity (%) | 98.1 | 98.4 | 98.9 | 97.5 | 99.7 | |
| 0-5 years | Yes (n) | 107 80 | 112 75 | 130 57 | 89 98 | 170 17 |
| No (n) | 62 2230 | 60 2232 | 84 2208 | 38 2254 | 1092 1200 | |
| Kappa | 0.57 (0.51-0.63) | 0.60 (0.53-0.66) | 0.62 (0.56-0.68) | 0.54 (0.47-0.60) | 0.12 (0.10-0.14) | |
| Sensitivity (%) | 63.3 | 65.1 | 60.8 | 70.1 | 13.5 | |
| Specificity (%) | 96.5 | 96.8 | 97.5 | 95.8 | 98.6 | |
*Asthma attack, current use of medication, wheezing, being awakened by tightness in chest, attacks of shortness of breath or coughing
Category: Diagnosing asthma
Tags: Administration, Asthma, Data linkage, Database, Survey, Validation data linkage
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