The normal range of complement C1q varies in different testing methods. In the commonly used immunoprojection turbidimetric assay and unidirectional immunoexpansion assay, the detection value of complement C1q of 152mg/L is below the lower limit of the reference range, which is abnormal. Complement C1q is a protein mainly involved in inflammation and immune response, and the reference range and unit of this complement varies in different laboratory methods. In the immunoprojection turbidimetric assay, the reference range of complement C1q is 159 mg/L~233 mg/L, and that of the unidirectional immunoexpansion assay is 157~237 mg/L. If the above two assays are used, the complement C1q value of 152mg/L is below the lower limit of the reference range, but the reduced level is not very significant. If the complement C1q test result is still low after laboratory review, it is suggestive of mixed connective tissue disease and other immune-related diseases, and autoantibodies, blood sedimentation, ultrasound, CT and other ancillary tests need to be further improved to clarify the cause. Laboratory test results should be interpreted by a professional physician, and it is recommended that patients with a complement C1q value of 152mg/L go to the rheumatology and immunology department of a regular hospital for detailed consultation.