Background: 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.

Methods: 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. Results of serum electrophoresis testing were also assessed where available.

Results: 4035 patients had paired laboratory data available. A calculated globulin ≤20g/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 (≥43g/L) who also had a serum electrophoresis performed. Significantly elevated calculated globulin ≥50g/L (>4th percentile) were seen in patients with either liver disease (37%), haematological malignancy (36%), autoimmune disease (13%) or infections (9%).

Conclusions: 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.

背景：通过从总蛋白中减去白蛋白，从肝功能测试中得出计算的球蛋白分数。由于免疫球蛋白是血清球蛋白浓度的最大组成部分，因此计算的球蛋白增加或减少，可能分别识别出患有低丙种球蛋白血症或高丙种球蛋白血症的患者。

方法：回顾性研究了三间三级医院住院患者2.5年的实验室数据。鉴定出具有配对计算球蛋白和免疫球蛋白结果的患者，并复习临床细节。还评估了血清电泳测试的结果。

结果：4035名患者获得了配对的实验室数据。计算得出的球蛋白≥20g / L（<第二个百分位数）对低丙种球蛋白血症（IgG≥5.7 g / L）的敏感性较低（5.8％）但有良好的阳性预测值（82.5％），阳性预测为严重低丙种球蛋白血症（IgG≥3 g / L）的血脂值为37.5％。在123/291（42.3％）的患者中，计算出的球蛋白增加（≥43g/ L）的患者中也鉴定了副蛋白，并且还进行了血清电泳。在患有肝病（37％），血液系统恶性肿瘤（36％），自身免疫性疾病（13％）或感染（9％）的患者中，计算球蛋白≥50g/ L（> 4％百分位数）显着升高。

结论：计算球蛋白是一种廉价且易于获得的检测方法，有助于鉴定低丙种球蛋白血症或高丙种球蛋白血症，这可能会促使进一步研究并减少诊断延迟。