Department of Clinical Immunology, Sir Charles Gairdner Hospital, Perth, Australia.
Department of Biochemistry, PathWest QEII Medical Centre, Perth, Australia.
Ann Clin Biochem. 2021 May;58(3):236-243. doi: 10.1177/0004563221989737. Epub 2021 Feb 1.
Calculated globulin fraction is derived from the liver function tests by subtracting albumin from the total protein. Since immunoglobulins comprise the largest component of the serum globulin concentration, increased or decreased calculated globulins and may identify patients with hypogammaglobulinaemia or hypergammaglobulinaemia, respectively.
A retrospective study of laboratory data over 2.5 years from inpatients at three tertiary hospitals was performed. Patients with paired calculated globulins and immunoglobulin results were identified and clinical details reviewed. The results of serum electrophoresis testing were also assessed where available.
A total of 4035 patients had paired laboratory data available. A calculated globulin ≤20 g/L (<2nd percentile) had a low sensitivity (5.8%) but good positive predictive value (82.5%) for hypogammaglobulinaemia (IgG ≤5.7 g/L), with a positive predictive value of 37.5% for severe hypogammaglobulinaemia (IgG ≤3 g/L). Paraproteins were identified in 123/291 (42.3%) of patients with increased calculated globulins (≥42 g/L) who also had a serum electrophoresis performed. Significantly elevated calculated globulin ≥50 g/L (>4th percentile) were seen in patients with either liver disease (37%), haematological malignancy (36%), autoimmune disease (13%) or infections (9%).
Calculated globulin is an inexpensive and easily available test that assists in the identification of hypogammaglobulinaemia or hypergammaglobulinaemia which may prompt further investigation and reduce diagnostic delays.
球蛋白分数是通过从总蛋白中减去白蛋白从肝功能测试中得出的。由于免疫球蛋白构成血清球蛋白浓度的最大组成部分，增加或减少计算的球蛋白可能分别识别低丙种球蛋白血症或高丙种球蛋白血症患者。
对三家三级医院住院患者 2.5 年的实验室数据进行回顾性研究。确定了具有配对计算球蛋白和免疫球蛋白结果的患者，并回顾了临床详细信息。在有条件的情况下，还评估了血清电泳检测的结果。
共有 4035 名患者有配对的实验室数据。计算球蛋白≤20 g/L（<第 2 个百分位）对低丙种球蛋白血症（IgG≤5.7 g/L）的敏感性较低（5.8%），但阳性预测值较高（82.5%），严重低丙种球蛋白血症（IgG≤3 g/L）的阳性预测值为 37.5%。在进行血清电泳的 291 名球蛋白升高（≥42 g/L）患者中，有 123/291（42.3%）例患者发现了副蛋白。显著升高的计算球蛋白≥50 g/L（>第 4 个百分位）见于患有肝病（37%）、血液恶性肿瘤（36%）、自身免疫性疾病（13%）或感染（9%）的患者。
计算球蛋白是一种廉价且易于获得的测试，有助于识别低丙种球蛋白血症或高丙种球蛋白血症，这可能提示进一步调查并减少诊断延迟。
