SERPINH1 and idiopathic pulmonary fibrosis: However, we do not recommend the use of this serum marker alone to differentiate idiopathic fibrosing NSIP and other types of IIP because (1) our study only included a relatively small number of patients, (2) there was some overlap in the serum levels of anti-HSP47 autoantibodies between UIP and NSIP, (3) this is a retrospective study.