As mentioned, it is important to look for signs of connective tissue disorders, which includes obtaining serology. This patient has a negative ANA for all intents and purposes, a negative ESR, and a negative rheumatoid factor, which is the current recommendation for serology for patients presenting with suspected idiopathic pulmonary fibrosis. The pulmonary function tests are prototypical for a moderately diseased patient experiencing some shortness of breath with exertion. The 6-minute walk differentiates the severity of the disease rather than the nature of the disease, and the patient desaturates from 98% to 92% after walking 1300 feet. Normal lungs will increase their oxygen saturation with exercise rather than decreasing their oxygen saturation, so this confirms the presence of interstitial lung disease but not one disease in particular.