Department of Internal Medicine, Saint Vincent Hospital, Worcester, MA, USA.
Semin Arthritis Rheum. 2010 Oct;40(2):176-83. doi: 10.1016/j.semarthrit.2009.10.004. Epub 2010 Feb 4.
To review the current evidence regarding the value of measuring procalcitonin (PCT) levels in patients with systemic autoimmune diseases, with a focus on the evidence for diagnostic and analytical performance of this biomarker. A brief description of the pathophysiological basis of this biomarker is also included.
Using PubMed from the National Library of Medicine, relevant English literature on PCT in patients with different systemic autoimmune diseases, from 1990 to 2009, was reviewed. The search used keywords referring to procalcitonin and systemic lupus erythematosus, antineutrophil cytoplasmic antibody-associated systemic vasculitis, Goodpasture syndrome, rheumatoid arthritis, and giant cell arteritis.
When used in the appropriate clinical setting, the measurement of serum PCT levels is valuable as a marker of severe systemic bacterial and fungal infections and sepsis. Information regarding plasma PCT levels in patients with active underlying systemic autoimmune diseases is limited, primarily from observational studies and case series, with considerable variability of patient characteristics and clinical settings. In the detection of systemic infection concomitant with autoimmune diseases, PCT had a diagnostic sensitivity of 53 to 100% and a specificity of 84 to 97% (depending on the selection criteria) and was superior to other inflammatory markers tested. Most of the studies used a semiquantitative test for PCT measurement (functional assay sensitivity <0.5 ng/mL), which can explain the low sensitivity of the test. PCT levels were not significantly affected by renal function abnormalities or immunosuppressive agents. Although high PCT levels commonly occurred with infection, elevated levels of PCT could be found in patients with vasculitis without evidence of infection, often correlated with high disease activity scores.
Significantly elevated PCT levels offer good specificity and sensitivity for systemic infection in patients with systemic autoimmune diseases, regardless of the use of corticosteroids or immunosuppressive agents. PCT measurement may add to diagnostic accuracy in patients with systemic autoimmune diseases who present with a febrile illness, especially when highly sensitive PCT assays and specific PCT cutoff ranges are used in a predefined clinical setting (reflecting the likelihood of infection versus an autoimmune disease flare). However, there are limitations when using this biomarker in patients with systemic autoimmune diseases. PCT levels should not replace the necessary extensive diagnostic workup, which should include a thorough history and physical examination, combined with appropriate immunological, microbiological, radiological, and histological data.
回顾目前关于测定降钙素原（PCT）水平在系统性自身免疫性疾病患者中的价值的证据，重点在于该生物标志物的诊断和分析性能的证据。本文还简要描述了该生物标志物的病理生理学基础。
利用美国国立医学图书馆的 PubMed 数据库，检索了 1990 年至 2009 年间关于不同系统性自身免疫性疾病患者 PCT 的相关英文文献。检索使用的关键词包括降钙素原和系统性红斑狼疮、抗中性粒细胞胞质抗体相关性系统性血管炎、Goodpasture 综合征、类风湿关节炎和巨细胞动脉炎。
当在适当的临床环境中使用时，血清 PCT 水平的测定作为严重全身性细菌和真菌感染及脓毒症的标志物是有价值的。关于活动期系统性自身免疫性疾病患者血浆 PCT 水平的信息有限，主要来自观察性研究和病例系列研究，患者特征和临床环境的差异很大。在检测伴有自身免疫性疾病的系统性感染时，PCT 的诊断灵敏度为 53%至 100%，特异性为 84%至 97%（取决于选择标准），优于其他测试的炎症标志物。大多数研究使用半定量 PCT 测量试验（功能性试验灵敏度<0.5ng/ml），这可以解释该试验的低灵敏度。PCT 水平不受肾功能异常或免疫抑制剂的影响。虽然 PCT 水平在感染时通常升高，但在无感染证据的血管炎患者中也可发现升高的 PCT 水平，常与高疾病活动评分相关。
无论是否使用皮质类固醇或免疫抑制剂，在患有系统性自身免疫性疾病的患者中，显著升高的 PCT 水平为全身性感染提供了良好的特异性和灵敏度。PCT 测定可提高有发热性疾病的系统性自身免疫性疾病患者的诊断准确性，尤其是在使用高灵敏度 PCT 检测和特定 PCT 截断范围的情况下，在预设的临床环境中（反映感染的可能性与自身免疫性疾病发作的可能性）。然而，在患有系统性自身免疫性疾病的患者中使用该生物标志物存在局限性。PCT 水平不应替代必要的广泛诊断性检查，该检查应包括详细的病史和体格检查，结合适当的免疫学、微生物学、放射学和组织学数据。
