Interstitial lung disease: clinical evaluation and keys to an accurate diagnosis
Section snippets
History of onset of illness
The presenting respiratory system complaints of a patient who has ILD should be characterized fully with a focus on the onset and duration of symptoms, rate of progression, and any associated extrathoracic symptoms, such as fever or joint discomfort. Acute symptoms (days to a few weeks) of cough, dyspnea, and fever necessitate evaluation for infection (viral, bacterial [particularly the atypical organisms], pneumocystis). In the absence of infection, cryptogenic organizing pneumonia (COP),
Respiratory symptoms other than dyspnea
Besides exertional dyspnea, other specific coexisting respiratory symptoms, such as cough, hemoptysis, and chest pain, may occur. Although cough is nonspecific, it can be the initial manifestation of ILD. Its presence raises the possibility of superimposed/coexisting airways disease that is associated with respiratory bronchiolitis–interstitial lung disease (RB-ILD), sarcoidosis, HP, and acid gastroesophageal reflux (GER). A chronic irritable cough has been associated with lymphangitic
Extrapulmonary symptoms
Several extrapulmonary symptoms provide useful clues. A history of dyspepsia and gastroesophageal reflux disease (GERD) may suggest IPF or scleroderma-related ILD. Most patients who have IPF do not have symptoms of GERD, although 90% have physiologic evidence of acid GER [5]. Overt aspiration or dysphagia suggests aspiration pneumonia, scleroderma, or mixed connective tissue disease; frank inflammatory arthritis suggests a CVD or sarcoidosis; ocular symptoms suggest sarcoidosis, CVD, or
Demographics and family medical history
The patient's age, cigarette-smoking status, and gender may provide important clues. IPF is almost always an adult disorder and typically occurs in patients who are older than 60 years of age. Patients who have NSIP usually are younger than 60. Although pulmonary sarcoidosis can manifest in the elderly patient, it is more common in the young and middle-aged. Pulmonary LCG typically occurs in young, cigarette-smoking men. RB-ILD and desquamative interstitial pneumonia (DIP) are seen almost
Environmental/occupation/medication history: identifying exposures
An exhaustive environmental and occupational exposure history is essential because it may lead to identification of a specific cause for ILD. At-risk occupations for ILD include miners (pneumoconiosis); sandblasters and granite workers (silicosis); dental workers (dental workers' pneumoconiosis); welders, shipyard workers, pipe fitters, electricians, automotive mechanics (asbestosis); farm workers (hypersensitivity pneumonitis); poultry workers, bird fanciers, bird breeders (hypersensitivity
Pulmonary signs
Auscultated crackles, typically described as “dry,” “Velcro,” end-inspiratory, and predominantly basilar, are detected in more than 80% of patients who have IPF [8]. Occasionally, crackles that are due to ILD may be detected on physical examination, even in the setting of a normal chest radiograph. Although crackles are reported in many different ILDs, they are detected less commonly in granulomatous ILDs (eg, sarcoidosis). Midinspiratory high-pitched squeaks are reported in the primary
Laboratory testing
Laboratory blood testing alone rarely permits one to either rule in or rule out a specific diagnosis, but may be strongly supportive in the appropriate clinical setting. Routine laboratory tests should be obtained and include a complete blood count with leukocyte differential, erythrocyte sedimentation rate (ESR), chemistry profile (serum electrolytes, serum urea nitrogen, creatinine, liver tests, and calcium). Chronic anemia (microcytic) may suggest occult pulmonary hemorrhage; abnormal liver
Chest radiograph: useful diagnostic patterns
A diffusely abnormal chest radiograph often is the initial finding that alerts the physician to the possibility of ILD. The clinician should make every effort to obtain previous chest radiographs for review. This may allow one to ascertain the onset, chronicity, rate of progression, or stability of the patient's disease. A rare patient who has dyspnea and restrictive pulmonary function test abnormalities will have a normal chest radiograph and high-resolution CT (HRCT), despite clinically
High-resolution CT
HRCT should be considered a standard procedure during the initial evaluation of almost all patients who have ILD. It is more sensitive than the plain radiograph in identifying ILD (with a sensitivity greater than 90%) and the image pattern of parenchymal abnormalities on HRCT often suggests a particular set of diagnostic possibilities (Table 4) [11]. HRCT also identifies “mixed” patterns of disease (eg, ILD plus emphysema) or additional pleural, hilar, or mediastinal abnormalities. It has a
Pulmonary function testing
Initial pulmonary function tests (PFTs) should include a spirometry (with and without bronchodilator), plethysmographic lung volumes, and DLCO (corrected to hemoglobin). PFTs cannot diagnose a specific ILD and cannot distinguish between active lung inflammation versus fibrosis, but are critically important in the objective assessment of respiratory symptoms as well as in paring the differential diagnosis, grading the severity of disease, and monitoring response to therapy or progression. PFT
Summary
The clinician who is confronted with a patient who has ILD needs to amass specific knowledge of several heterogenous acute and chronic diffuse lung disorders. The history must be detailed with leading questions asked to provoke occult, forgotten, or otherwise considered irrelevant information from the patient's social, family, occupational, environmental, and medical histories that might lead to the identification of the specific cause of the patient's ILD. With specific symptoms, signs, and
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