Introduction: Idiopathic pulmonary fibrosis(IPF) is chronic fibrosing interstitial pneumonia of unknown aetiology. IPF is diagnosed based on the exclusion of known causes such as connective tissue diseases(CTDs). However, some patients fail to meet defined CTD criteria regardless of an implication of immunological involvement and these cases were described in a variety of terms. The classification criteria of this clinical entity consist of a combination of clinical, serological and morphological findings and it is reported to be distinct from IPF. However, the significance of the sole presence of autoantibodies complicated with IPF is still unknown. Therefore, this systematic review aims to clarify the significance of autoantibodies complicated with IPF.

Methods and analysis: IPF with any autoantibody associated with CTDs is eligible for the review. Primary outcomes are all-cause mortality and pulmonary-cause mortality, while secondary outcomes include a progression of the disease, a deterioration of health-related quality of life and the development of a defined CTD. Primary studies of any type except a case report are included. Two reviewers search four electronic databases such as Medline, EMBASE, Science Citation Index Expanded and Google Scholar from each inception through 1 February 2018 and extract data independently. A risk of bias in individual studies is assessed by the Quality in Prognostic Studies tool. Meta-analysis is sought to be conducted if three or more studies report an outcome for a specific autoantibody with the same statistics. If it is inappropriate to combine data due to substantial heterogeneity, the result is reported qualitatively. Subgroup and sensitivity analyses are considered to identify the source of heterogeneity. The Grades of Recommendation, Assessment, Development and Evaluation method is applied to evaluate the evidence level of the result.

Ethics and dissemination: There is no concerning ethical issue. The result will be sought for publication.

Prospero registration number: CRD42017077336.