The 12 practice investigators were all family physicians working in communities with populations <100,000. The 382 patients were mainly women (63%) and adults (76%) with a mean age of 46.1 years (SD, 19.9 years; range, 7 to 89 years). Overall, 248 patients (65%) had a previous diagnosis of asthma only, 100 patients (26%) had COPD only, and 32 patients (8%) had both asthma and COPD.
Of the 382 patients, 2 patients withdrew before testing and 12 others never completed a test maneuver. Ten of these 12 patients were 70 years old (n = 6). Of the 368 completed tests, 261 tests (71%) were considered to be technically “good” (Fig 1, 2). For 66 tests (18%), the results were not reproducible; in 16 tests (4%), the best maneuver was 80%.
Interpretations of the spirometry results were concordant in 280 patients (76% of all completed tests) [Table 1; Fig 2], including 28 tests rated as “not interpretable” by both the family physician and the lung specialist. The percentage of nonconcordance was higher in people with prior COPD diagnoses compared to those with prior asthma diagnoses (30.0% vs 19.8%, respectively; p < 0.05; Table 1), Common types of nonconcordance included overreporting of airflow obstruction in those with normal spirometry results, interpreting restrictive patterns in people with poor effort, and an affirmation of COPD in the absence of an FEV/FVC ratio <70% (Table 1). Approximately 3% of the spirometry tracings had complex or combination abnormalities (such as restriction combined with obstruction) that the family physician often did not even attempt to interpret except as “unknown” or “abnormal.”
ndd Medizintechnik AG and the expert review were concordant in 93.7% of tests. All but one of the nonconcordant interpretations were read as “restrictive pattern” by ndd Medizintechnik AG, but the experts determined the tests to be inadequate due to poor effort.
Comparing before-and-after data demonstrated 207 reported changes in management in 182 of the 382 patients tested (48%), with decisions in 186 of 207 patients based on technically accurate and correctly interpreted tests (Fig 2). Over half (n = 107, 51.6%) were changes in medications that are described in Table 2 (Description popular inhalers can be found in our category “Asthma Inhalers“). Most medication increases were for “mild” disease reclassified as moderate or severe asthma or COPD after spirometry assessment. Normal spirometry results were associated with six medication decreases or discontinuations.
Overall, 86% of the medication changes were consistent with the Global Initiative for Chronic Obstructive Lung Disease guidelines for COPD management or the 2002 National Asthma Education and Prevention Program guidelines for asthma management. Two thirds of the medication changes that appeared to be inconsistent with guidelines were made following technically inadequate or incorrectly interpreted spirometry results.
Nonmedication management changes were made in 102 patients, 75 not associated with medication changes and 27 with a coincident change in medications (Table 2). Of particular note are the 19 patients referred for other potential diagnoses following normal spirometry findings, and 28 patients who were referred for co-management of severe obstructive lung disease.
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Figure 1. Spirometry outcomes.
Figure 2. Spirometry by site.
Table 1—Categories of Agreement of Interpretation
| Categories of Specialist Interpretation | Preexisting Diagnosis of Asthma (n = 248) | Preexisting Diagnosis of COPD (n = 100) | Preexisting Diagnosis of Asthma and COPD (n = 32) |
| Concordant | 199 (80.2) | 70 (70.0) | 23 (75.0) |
| Nonconcordance | 49(19.8) | 30 (30.0) | 9 (25.0) |
| Expert opinion that was not reported | |||
| by the family physician | |||
| Not interpretable | 17 (6.9) | 4 (4.0) | 2 (6.2) |
| No obstruction | 22 (8.9) | 18(18) | 5 (15.6) |
| Shows obstruction | 9 (3.6) | 3 (3) | 1 (3.1) |
| Otherf | 1 (0.4) | 5(5) | 1 (3.1) |
Table 2—Management Changes Following Spirometry 182 Patients
| Variables | Patients, No. |
| Medication changes (n = 107) Additions of new drugs (n = 47) | |
| Short-acting bronchodilator | 2 |
| Inhaled steroids | 16 |
| Long-acting bronchodilator | 11 |
| Second bronchodilator | 6 |
| Combination therapy | 12 |
| Increased dose of same drug (n = 42) | |
| Short-acting bronchodilator | 5 |
| Inhaled steroids | 10 |
| Long-acting bronchodilator | 7 |
| Combination therapy | 20 |
| Decreased or discontinued drug (n = 6) | |
| Short-acting bronchodilator | 2 |
| Long-acting bronchodilator | 2 |
| Combination therapy | 2 |
| Replaced drug (n = 12) | |
| All theophylline | 12 |
| Nonmedication changes (n = 75) | |
| Intense smoking cessation | 16 |
| Repeat spirometry test in 3 to 6 mo | 14 |
| Order additional diagnostic tests* | 12 |
| Plan more frequent follow-up visits | 12 |
| Reassess diagnosis* | 11 |
| Refer to pulmonologist or cardiologist* | 10 |
| Medication and nonmedication change combinations (n = 27) | |
| Smoking cessation and medication increase | 12 |
| Increased visit frequency and medication increase | 5 |
| Repeat spirometry and medication increase | 5 |
| Asthma education and medication increase | 4 |
| Increased visit frequency and medication decrease | 1 |