Fibrinogen and its combination with specific subgingival microorganisms may be potential markers indicating gingivitis and periodontitis.<h4>Conclusions</h4>Compared with IL-1β, IL-17, MMP8 and MMP9, fibrinogen in GCF demonstrated distinct associations with clinical parameters and subgingival microbiome in periodontal diseases. The gene discussed is MMP9; the disease is gingivitis.