In order to make a diagnosis of DAD a biopsy of the lung must be obtained, processed, and examined microscopically. As described above, the hallmark of diagnosing DAD is the presence of hyaline membranes.[1] Most frequently DAD is associated with ARDS, but since there are clinical criteria (see Berlin criteria above) upon which we can diagnose ARDS, it is often unnecessary in all cases to obtained invasive biopsies of the lung. Additionally, there are limitations of the biopsy test since it is possible to sample a potentially normal area of lung even though there is DAD in the rest of the lung, resulting in a false negative.[1]