Finally, to paraphrase what Cals and Hopstaken state, we should treat patients, not misdiagnoses. The Clinical Inquiry was addressed to those adult patients who presented with an acute cough, not necessarily only to patients with a LRTI since there is no standard definition for a LRTI or acute bronchitis for the practicing clinician.8,9 Many patients diagnosed with “acute bronchitis” just have an upper respiratory tract infection (URTI)—the common cold.10 Conversely, 18% of patients diagnosed with a URTI with no history of asthma or chronic obstructive pulmonary disease in one study had a greater than 15% increase in forced expiratory volume in 1 second (FEV1) over several weeks, implying that they also had a lower respiratory tract component.11 Even in the cited study by Melbye et al,1 only 14 (70%) of the radiographic pneumonias found were in the patients diagnosed initially with a LRTI. The other 7 (30%) were somehow diagnosed in those presumably with an URTI. In addition, even in this study not all LRTI patients had chest x-rays done.
In studying acute cough illnesses, until we get a better way of diagnosing those respiratory tract infections that also involve the lower respiratory tract other than possibly pulmonary function testing, sticking to a readily identifiable presenting symptom will prevent misdiagnoses and misclassification. Additionally, if we want to see how an acute cough illness relates to pneumonia, then all patients would need to have a chest x-ray.
Paul Pisarik, MD
Baylor College of Medicine, Houston, Tex