►在不同的系统性自身免疫性风湿疾病中有不同程度的表现，特别是系统性红斑狼疮、系统性硬化症、混合性结缔组织病、系统性硬化症-自身免疫性肌病重叠综合征和未分化结缔组织病（例如，具有风湿症状但未明确诊断为系统性自身免疫性风湿病的患者）(29)

►对于临床疑似系统性红斑狼疮的患者，建议后续检测抗Sm和U1RNP抗体；这些抗原通常包含在常规的抗可溶性抗原谱检测中；系统性红斑狼疮的分类标准包含抗Sm抗体(16,30,31)

►对于临床疑似系统性硬化症的患者，建议后续检测抗RNApol III抗体（例如，系统性硬化症谱*）；抗RNApol III抗体包含于系统性硬化症的分类标准中(8)

►对于临床疑似混合性结缔组织病的患者，建议后续检测抗U1RNP抗体。U1RNP抗原通常包含在常规的ENA谱检测中；抗U1RNP抗体包含于混合性结缔组织病的诊断标准中(32)

►对于临床疑似系统性硬化症-自身免疫性肌病重叠综合征的患者，建议后续检测抗U1RNP抗体和抗Ku抗体；U1RNP抗原包含在常规的抗可溶性抗原谱检测中，抗Ku抗体则包含于疾病特异性免疫检测中（例如，炎症性肌病谱*和系统性硬化症谱*）(26,33)

►对于一般人群中的非系统性自身免疫性风湿疾病个体，AC-5核型的存在与上述自身抗原无关，且通常抗体滴度低。

*炎症性肌病谱、系统性硬化症谱和（扩展的）肝病谱的应用可能仅限于专业的临床实验室。

► Present to a varying degree in distinct SARD, in particular SLE, SSc, MCTD, SSc-AIM overlap syndrome, and UCTD (i.e, patients with rheumatic symptoms without a definite SARD diagnosis) (29)

► If SLE is clinically suspected, it is recommended to perform follow-up tests for anti-Sm and anti-U1RNP antibodies; these antigens are commonly included in the routine ENA profile; anti-Sm antibodies are included in the classification criteria for SLE (16, 30, 31)

► If SSc is clinically suspected, it is recommended to perform a follow-up test for anti-RNApol III antibodies (e.g., SSc profile*); the anti-RNApol III antibodies are included in the classification criteria for SSc (8)

► If MCTD is clinically suspected, it is recommended to perform a follow-up test for anti-U1RNP antibodies; the antigen is commonly included in the routine ENA profile; anti-U1RNP antibodies are included in the diagnostic criteria for MCTD (32)

► If the SSc-AIM overlap syndrome is clinically suspected, it is recommended to perform follow-up tests for anti-U1RNP and anti-Ku antibodies; these antigens are included in the routine ENA profile (U1RNP), or in disease specific immunoassays (Ku, i.e., inflammatory myopathy profile* and SSc profile*) (26, 33)

► In non-SARD individuals in the general population, the presence of the AC-5 pattern is not associated with the autoantigens mentioned above and most often concerns low antibody titers

*Availability of the inflammatory myopathy profile, the SSc profile and the (extended) liver profile may be limited to specialty clinical laboratories.

8. van den Hoogen F, Khanna D, Fransen J, et al. 2013 classification criteria for systemic sclerosis: an American College of rheumatology/European League against rheumatism collaborative initiative. Ann Rheum Dis 2013;72:1747–55.

16. Petri M, Orbai AM, Alarcón GS, et al. Derivation and validation of the systemic lupus international collaborating clinics classification criteria for systemic lupus erythematosus. Arthritis Rheum 2012;64:2677–86.

26. Betteridge Z, McHugh N. Myositis-specific autoantibodies: an important tool to support diagnosis of myositis. J Intern Med 2016;280:8–23.

29. Northway JD, Tan EM. Differentiation of antinuclear antibodies giving Speckled staining patterns in immunofluorescence. Clin Immunol Immunopathol 1972;1:140–54.

30, Satoh M, Fritzler MJ, Chan EKL. Antihistone and antispliceosomal antibodies. In: Lahita RG, Tsokos G, Buyon JP, et al, eds. Systemic lupus erythematosus. San Diego: Academic Press, 2011: 275–92.

31. Satoh M, Vázquez-Del Mercado M, Chan EK. Clinical interpretation of antinuclear antibody tests in systemic rheumatic diseases. Mod Rheumatol 2009;19:219–28.

32. Sharp GC, Irvin WS, Tan EM, et al. Mixed connective tissue disease--an apparently distinct rheumatic disease syndrome associated with a specific antibody to an extractable nuclear antigen (ENA). Am J Med 1972;52:148–59.

8. van den Hoogen F, Khanna D, Fransen J, et al. 2013 classification criteria for systemic sclerosis: an American College of rheumatology/European League against rheumatism collaborative initiative. Ann Rheum Dis 2013;72:1747–55.

16. Petri M, Orbai AM, Alarcón GS, et al. Derivation and validation of the systemic lupus international collaborating clinics classification criteria for systemic lupus erythematosus. Arthritis Rheum 2012;64:2677–86.

26. Betteridge Z, McHugh N. Myositis-specific autoantibodies: an important tool to support diagnosis of myositis. J Intern Med 2016;280:8–23.

29. Northway JD, Tan EM. Differentiation of antinuclear antibodies giving Speckled staining patterns in immunofluorescence. Clin Immunol Immunopathol 1972;1:140–54.

30, Satoh M, Fritzler MJ, Chan EKL. Antihistone and antispliceosomal antibodies. In: Lahita RG, Tsokos G, Buyon JP, et al, eds. Systemic lupus erythematosus. San Diego: Academic Press, 2011: 275–92.

31. Satoh M, Vázquez-Del Mercado M, Chan EK. Clinical interpretation of antinuclear antibody tests in systemic rheumatic diseases. Mod Rheumatol 2009;19:219–28.

32. Sharp GC, Irvin WS, Tan EM, et al. Mixed connective tissue disease--an apparently distinct rheumatic disease syndrome associated with a specific antibody to an extractable nuclear antigen (ENA). Am J Med 1972;52:148–59.

►少数情况下，AC-5核型相关的自身抗体可能为非U1RNP的RNP，例如U2RNP（与系统性硬化症-自身免疫性肌病重叠综合征相关）或U11/U12RNP（与系统性硬化症相关）；这些自身抗体可以通过免疫沉淀反应进行检测（13,14）

注：这些自身抗体的特异性免疫检测目前尚未商品化。

► Occasionally, autoantibodies revealing the AC‐5 pattern are reactive with RNP other than U1RNP, for instance U2RNP (associated with SSc‐AIM overlap syndrome) or U11/U12RNP (associated with SSc); these autoantibodies can be detected by immunoprecipitation (13, 14)

Note: Specific immunoassays for these autoantibodies are currently not commercially available.

13. Mimori T, Hinterberger M, Pettersson I, et al. Autoantibodies to the U2 small nuclear ribonucleoprotein in a patient with scleroderma‐polymyositis overlap syndrome. J Biol Chem 1984;259:560‐5.

14. Fretig N, Domsic RT, Rodriguez‐Reyna T, et al. Anti‐U11/U12 RNP antibodies in systemic sclerosis: a new serologic marker associated with pulmonary fibrosis. Arthritis Rheum 2009;61:958‐65.

13. Mimori T, Hinterberger M, Pettersson I, et al. Autoantibodies to the U2 small nuclear ribonucleoprotein in a patient with scleroderma‐polymyositis overlap syndrome. J Biol Chem 1984;259:560‐5.

14. Fretig N, Domsic RT, Rodriguez‐Reyna T, et al. Anti‐U11/U12 RNP antibodies in systemic sclerosis: a new serologic marker associated with pulmonary fibrosis. Arthritis Rheum 2009;61:958‐65.