Abstract: The present invention is based, in part, on our analysis of C1-INH levels in various patient populations. Accordingly, in a first aspect, the invention features methods for assessing the protective capacity of endogenous C1-INH in a patient who has been diagnosed with ARDS, sepsis or a sepsis-related condition, a burn or a burn-related condition, SJS, CABG-related states and/or other traumatic injuries. The methods can include the steps of: (a) providing a fluid sample from the patient; (b) determining the amount of C1-INH functional activity in the sample; and (c) comparing the amount of C1-INH functional activity to a reference standard. Where the level of C1-INH functional activity is comparable to that within a healthy patient population, the patient's own protective capacity is compromised.