APOA1 and susceptibility to pneumonia measurement: In this study, patients with severe pneumonia had elevated LDH levels or reduced ApoA1 levels during hospitalization with acute exacerbation of chronic obstructive pulmonary disease or MODS, as both acute exacerbation of chronic obstructive pulmonary disease and MODS are severe wasting diseases, which, when combined with severe pneumonia, lead to an extremely serious inflammatory »waterfall effect« that severely impairs the immune function of the body [19], [20], and this blow is often fatal.