Differences in local and systemic inflammatory markers in patients with obstructive airways disease.

BACKGROUND: Asthma and chronic obstructive pulmonary disease (COPD) are characterised by airway and systemic inflammation, but little is known about differences and similarities in inflammatory markers in patients with obstructive airways disease. METHODS: In 210 adult patients presenting to their general practitioners with symptoms suggestive of obstructive airways disease, lung function, fractional exhaled nitric oxide (FE(NO)), blood eosinophils, and serum levels of high-sensitivity C-reactive protein (hs-CRP) and IgE were measured. RESULTS: hs-CRP levels were increased in COPD patients (p=0.009), whereas FE(NO), IgE, and eosinophils were increased in patients with asthma (p=0.009, p=0.041, and p=0.009, respectively). In the ROC analysis, hs-CRP had the largest area under the curve (AUC=0.651; 95% confidence interval (CI) 0.552 to 0.749), with a specifity of 83% and a sensitivity of 42% for the diagnosis of COPD. FE(NO) was the most accurate marker in the diagnosis of asthma (AUC=0.618; 95% CI 0.529 to 0.706). Serum hs-CRP levels correlated with the number of smoking pack-years (r=0.218, p=0.001) and inversely with lung function parameters. CONCLUSIONS: Levels of serum hs-CRP, IgE, blood eosinophils, and FE(NO) identify distinct aspects of local and systemic inflammation in patients with obstructive airways disease. This might help to differentiate between asthma and COPD in primary care patients when spirometry is not available.

Diagnosing asthma in general practice with portable exhaled nitric oxide measurement--results of a prospective diagnostic study: FENO < or = 16 ppb better than FENO < or =12 ppb to rule out mild and moderate to severe asthma [added].

BACKGROUND: To evaluate the sensitivity, specificity and predictive values of fractional exhaled nitric oxide (FENO) for the diagnosis of asthma in general practice. METHODS: Prospective diagnostic study with 160 patients attending 10 general practices for the first time with complaints suspicious of obstructive airway disease (OAD). Patients were referred to a lung function laboratory for diagnostic investigation. The index test was FENO measured with a portable FENO analyser based on electrochemical sensor. The reference standard was the Tiffeneau ratio (FEV1/VC) as received by spirometric manoeuvre and/or results of bronchial provocation. Bronchial provocation with methacholine was performed to determine bronchial hyper-responsiveness (BHR) in the event of inconclusive spirometric results. RESULTS: 88 (55%) were female; their average age was 43.9 years. 75 (46.9%) patients had asthma, 25 (15.6%) had COPD, 8 (5.0%) had an overlap of COPD and asthma, and 52 (32.5%) had no OAD. At a cut-off level of 46 parts per billion (ppb) (n = 30; 18.8%), sensitivity was 32% (95%CI 23-43%), specificity 93% (95%CI 85-97%), positive predictive value (PPV) 80% (95%CI 63-91%), negative predictive value (NPV) 61% (95%CI 52-69%) when compared with a 20% fall in FEV1 from the baseline value (PC20) after inhaling methacholine concentration 46 ppb. Mild and moderate to severe asthma could be ruled out with FENO

Diagnostic accuracy of spirometry in primary care.

BACKGROUND: To evaluate the sensitivity, specificity and predictive values of spirometry for the diagnosis of chronic obstructive pulmonary disease (COPD) and asthma in patients suspected of suffering from an obstructive airway disease (OAD) in primary care. METHODS: Cross sectional diagnostic study of 219 adult patients attending 10 general practices for the first time with complaints suspicious for OAD. All patients underwent spirometry and structured medical histories were documented. All patients received whole-body plethysmography (WBP) in a lung function laboratory. The reference standard was the Tiffeneau ratio (FEV1/VC) received by the spirometric maneuver during examination with WBP. In the event of inconclusive results, bronchial provocation was performed to determine bronchial hyper-responsiveness (BHR). Asthma was defined as a PC20 fall after inhaling methacholine concentration < or = 16 mg/ml. RESULTS: 90 (41.1%) patients suffered from asthma, 50 (22.8%) suffered from COPD, 79 (36.1%) had no OAD. The sensitivity for diagnosing airway obstruction in COPD was 92% (95%CI 80-97); specificity was 84% (95%CI 77-89). The positive predictive value (PPV) was 63% (95%CI 51-73); negative predictive value (NPV) was 97% (95%CI 93-99). The sensitivity for diagnosing airway obstruction in asthma was 29% (95%CI 21-39); specificity was 90% (95%CI 81-95). PPV was 77% (95%CI 60-88); NPV was 53% (95%CI 45-61). CONCLUSION: COPD can be estimated with high diagnostic accuracy using spirometry. It is also possible to rule in asthma with spirometry. However, asthma can not be ruled out only using spirometry. This diagnostic uncertainty leads to an overestimation of asthma presence. Patients with inconclusive spirometric results should be referred for nitric oxide (NO) - measurement and/or bronchial provocation if possible to guarantee accurate diagnosis.