In a Patient with clinical signs of Asthma which of the following tests will confirm the diagnosis:

Answer is C (Diurnal variation in PEF > 20 Percent): Demonstrate Outflow Obstruction Decreased FEV1 Decreased PEF Decreased FEV1 /FVC While respiratory symptoms suggest asthma, the sine qua non for the diagnosis of asthma is the presence of Reversible Airflow Obstruction and/or Airway Hyper-responsiveness or Increased Peak Expiratory Flow (PEF) Variability in subjects without airways obstruction. Reversible Airflow Obstruction Reversibility is demonstrated by repeating spirometry results 15 minutes after administering a sho acting bronchodilator > 12% reversibility in FEV1 >200 ml increase in Baseline FEV1 Positive Reversibility Results Strongly (Considered Diagnostic) Increased Peak Expiratory Flow Rate (PEF) Variability Demonstration of Diurnal Variation in the Peak Expiratory Flow Rate A diurnal variation in PEF of more than 20 percent Strongly suggests a diagnosis of Asthma (Considered Diagnostic) Airway Hyper-responsiveness Measured by Methacholine orHistamine challenge. Increasing Concentrations of Methacholine are administered and if the FEV1 drops to >20 percent of baseline with any standard dose the test is consideredpositive. Positive test strongly suggests a diagnosis of Asthma