Differentiating UIP and NSIP

Several key features can help to distinguish NSIP from UIP. While helpful, the differences between UIP and NSIP are often not as obvious as this figure suggests, and the difficulty lies in distinguishing the cases that lie toward the middle. NSIP is temporally and spatially homogeneous, while UIP is typically heterogeneous, patchy, and irregular in size.³⁶ The extent of honeycombing and traction bronchiectasis is greater in UIP than the extent of ground glass opacity or micronodules, which are more commonly associated with an NSIP pattern.⁵³⁶