Which test is most useful in diagnosing asthma in Sunita?

Spirometry is the most useful test for diagnosing asthma because it measures lung function, specifically the amount of air that can be forcibly exhaled in one second (FEV1) and other vital capacity measurements. This test assesses the presence and severity of airway obstruction, which is a hallmark of asthma. By comparing the results before and after administering a bronchodilator, spirometry can also help determine if the obstruction is reversible, a characteristic feature of asthma.

In contrast, while a chest X-ray can provide images of the lungs and can be useful in ruling out other conditions, it does not provide specific information about airflow or the function of the lungs related to asthma. A complete blood count can help detect signs of infection or anemia but does not directly assess lung function or diagnose asthma. The skin prick test is primarily used to identify specific allergens that may contribute to asthma symptoms but is not a diagnostic tool for asthma itself. Thus, spirometry stands out as the gold standard for diagnosing and evaluating the functional status of patients with suspected asthma.