title: Diagnostic accuracy of spirometry in primary care.
abstract: 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).
  
  
  CONCLUSIONS
  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.
authors: Institute of General Practice, Technische Universität München, München, Germany. antonius.schneider@lrz.tum.de
authors: Antonius
authors: A
authors: Schneider
authors: Lena
authors: L
authors: Gindner
authors: Lisa
authors: L
authors: Tilemann
authors: Tjard
authors: T
authors: Schermer
authors: Geert-Jan
authors: GJ
authors: Dinant
authors: Franz Joachim
authors: FJ
authors: Meyer
authors: Joachim
authors: J
authors: Szecsenyi
mesh_terms: D000328:Adult; D000368:Aged; D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D003951:Diagnostic Errors / Q000517:prevention & control; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010993:Plethysmography, Whole Body; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology*; D012680:Sensitivity and Specificity; D013147:Spirometry / Q000592:standards*