Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, USA; New York-Presbyterian Hospital, Weill Cornell Medicine, New York, NY, USA.
Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, USA; New York-Presbyterian Hospital, Weill Cornell Medicine, New York, NY, USA.
Clin Chim Acta. 2021 Aug;519:308-310. doi: 10.1016/j.cca.2021.05.025. Epub 2021 May 26.
Major discrepancies between concentrations of serum total carbon dioxide (tCO) obtained from chemistry analyzers and calculated bicarbonate from blood gas analyzers should prompt laboratory investigation. Here, we present a rare case of pseudohypobicarbonatemia unrelated to the common causes such as hypertriglyceridemia and hyperproteinemia, but was caused by a low concentration of paraproteins.
A 75-year-old man with persistent fevers was found to have a low concentration of serum tCO (<10 mmol/l) with a normal pH and calculated bicarbonate concentrations (23.5 mmol/l) from the blood gas analyzer. His serum tCO concentrations remained critically low throughout hospitalization without any evidence of acidosis. Serum tCO levels were measured via Siemens ADVIA Chemistry XPT system.
Mixing studies revealed non-linearity of serum tCO, suggesting the presence of interfering substances. Triglyceride concentrations were normal. Serum electrophoresis revealed a 0.4 mg/dl M-protein. The patient's serum tCO concentrations were repeated on different chemistry analyzer platforms - including Siemens, Roche, and Abbott - which demonstrated that the interference was specific to the Siemens chemistry analyzer. Serum tCO was significantly elevated after ultrafiltration of paraprotein, which confirmed the root cause of pseudohypobicarbonatemia.
Laboratory professionals should be aware that spuriously low serum tCO concentrations may result from unique interfering substances, such as paraproteins, that are both patient- and chemistry analyzer-specific.
从化学分析仪获得的血清总二氧化碳 (tCO) 浓度与血气分析仪计算的碳酸氢盐之间存在显著差异时，应促使实验室进行调查。在此，我们报告了一例罕见的假性低碳酸氢盐血症病例，其与常见原因（如高血脂和高蛋白血症）无关，而是由低浓度的副蛋白引起的。
一名 75 岁的男性持续发热，其血气分析仪检测的血清 tCO（<10 mmol/l）浓度较低，pH 值和计算的碳酸氢盐浓度（23.5 mmol/l）正常。在整个住院期间，他的血清 tCO 浓度一直保持极低水平，没有任何酸中毒的证据。血清 tCO 水平通过西门子 ADVIA Chemistry XPT 系统进行测量。
混合研究显示血清 tCO 呈非线性，提示存在干扰物质。甘油三酯浓度正常。血清电泳显示存在 0.4mg/dl 的 M 蛋白。患者的血清 tCO 浓度在不同的化学分析仪平台（包括西门子、罗氏和雅培）上进行了重复检测，结果表明干扰是特定于西门子化学分析仪的。在超滤去除副蛋白后，血清 tCO 显著升高，证实了假性低碳酸氢盐血症的根本原因。
实验室专业人员应该意识到，血清 tCO 浓度的假性降低可能是由独特的干扰物质引起的，这些物质具有患者和化学分析仪特异性。
