The ICD-9 code is determined from the information on physician billing data or is assigned by the staff at the physician services department, and if an asthma episode was related to bronchitis, there might have been a mis-classification in the coding between asthma and bronchitis or between COPD and bronchitis. Different diagnostic criteria between physicians may have affected how the visit was coded. In order to verify the accuracy of the asthma diagnosis, we used asthma-related drug purchase to determine the accuracy of asthma diagnosis and documented that > 70% of the persons had purchased at least one asthma-related drug in the 12 months following a visit to the physician. The reasons for the other 30% of the population having no record of purchasing an asthma drug are not known but might include mild asthma not requiring an asthma medication, asthma subjects not purchasing medication prescribed by the physician (noncompliance), or coders assigning the asthma code for other conditions.
We conclude that, first, asthma prevalence, which was on the increase in the 1980s and early 1990s, either stabilized or declined during the latter part of 1990s in Saskatchewan. Second, preschool children and older adults of Registered Indian origin had increased asthma prevalence. Finally, during the study period, rural populations in Saskatchewan had similar or lower asthma prevalence in comparison to urban populations in all age groups. Further research is required to elucidate the findings in this study.
Study objective: Single-breath diffusing capacity of the lung for carbon monoxide (Dlco) is used as a pulmonary function test (PFT) to assess gas transfer in the lungs. The implications of a low Dlco are well-recognized, but the clinical significance of a high Dlco is not clear. The aim of this study was to identify the clinical correlates of a high Dlco.
Patients and methods: We identified 245 patients with a high Dlco (ie, > 140% predicted) and a matched group of 245 patients with normal Dlco (ie, 85 to 115% predicted), who were selected from a laboratory database of 45,000 patients tested between January 1997 and December 1999. We compared the demographic features, clinical diagnoses, and PFT data between the two groups.
Settings: Large multispecialty group practice.
Results: The patients in the high Dlco group were heavier (mean [± SD] weight, 96.0 ± 22.9 vs 85.0 ± 21.3 kg, respectively; p < 0.001), had a higher mean body mass index (32.9 ± 7.4 vs 29.4 ± 6.4 kg/m2, respectively; p < 0.001), larger body surface area (p < 0.001), and larger mean total lung capacity (p = 0.007) and alveolar volume (p < 0.001). The clinical diagnoses of obesity (p < 0.001) and asthma (p < 0.001) were more common among patients with high Dlco values. The majority of patients (62%) with a high Dlco had a diagnosis of obesity, asthma, or both. Polycythemia, hemoptysis, and left-to-right shunt were uncommon.