How Are Chronic Lung Infections Diagnosed?
Although different chronic lung infections are caused by different agents, they can be confusing because of similarities in their signs, symptoms, X-ray findings, and pulmonary compromise. The end result is a common syndrome whose cause may be difficult to identify specifically unless further testing is used.
Since the term “chronic lung infections” is reserved for those that fail to respond to treatment (antibiotics, etc.), the cause of treatment failure is as important as the infectious agent. Diagnosis must include a search for the patient’s underlying host factors, such as age, immunosuppression, and comorbidities. In tandem with this appraisal is identification of the infectious agent, and together, they can individualize treatment according to both the cause of the infection and the cause of the treatment failure.
Diagnosis begins with clinical findings such as dyspnea, sputum production, coughing, and fever. Associated symptoms include congestion, productive cough, chest pain, wheezing, and weight loss. Physical exam to auscultate the lung fields can identify the extent of disease, and X-ray imaging will complement this approach.
Definitive identification of what to treat is based on bacterial cultures, and if these persist as negative, a viral cause is assumed. Viral causes include HIV and the herpes viruses (HSV 1 and 2, Epstein-Barr, cytomegalovirus, or varicella).
Sputum culture: used to pursue the identity of the infectious agent, and sensitivity testing of this organism can demonstrate any antibiotic resistances that have developed from previous antibiotic exposures. If targeted medication fails, further testing is warranted with CT imaging of the chest. If there is a mass or suspicious area on imaging studies, bronchoscopy is used to get deeper washings and/or tissue biopsies.
Blood tests: helpful in identifying the severity of infection via a white blood count and even an allergic or parasitic component based on eosinophils (WBCs common in allergic reactions and parasites).
Pulmonary function testing: to evaluate the degree of lung compromise with functional testing such as spirometry. Spirometry can measure parameters such as vital capacity, expiratory volume, and other flow measures. These results can determine the need for supplemental oxygen.