补体成分3 (C3)

定义

Complement C3 is a blood test that measures the activity of a certain protein.

This protein is part of the complement system. 补体系统 is a group of nearly 60 proteins that are in blood plasma or on the surface of some cells. The proteins work with your immune system 和 play a role to protect the body from infections, 和 to remove dead cells 和 foreign material. Rarely, people may inherit deficiency of some complement proteins. These people are prone to certain infections or 自身免疫性疾病s.

There are nine major complement proteins. 它们被标记为C1到C9. This article describes the test that measures C3.

选择的名字

C3

如何执行测试

血液从静脉中抽取. Most often, a vein from the inside of the elbow or the back of the h和 is used.

操作步骤如下:

• The site is cleaned with an antiseptic.
• The health care provider wraps an elastic b和 around the upper arm to apply pressure to the area 和 make the vein swell with blood.
• The provider gently inserts a needle into the vein.
• The blood collects into an airtight vial or tube attached to the needle. The elastic b和 is removed from your arm.
• Once the blood has been collected, the needle is removed. The puncture site is covered to stop any bleeding.

用于婴儿或幼童, a sharp tool called a lancet may be used to puncture the skin 和 make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A b和age may be placed over the area if there is any bleeding.

如何准备考试

There is no special preparation needed.

考试的感觉如何

When the needle is inserted to draw blood, some people feel moderate pain. Others may feel only a prick or stinging sensation. Afterward, there may be some throbbing.

为什么要进行测试

C3 和 C4 are the most commonly measured complement components.

A complement test may be used to monitor people with an 自身免疫性疾病. It is done to see if treatment for their condition is working. When the complement system is turned on during inflammation, levels of complement proteins may go down. 例如，活跃的人 红斑狼疮 may have lower-than-normal levels of the complement proteins C3 和 C4.

The test may also be done for the following conditions:

• 真菌感染
• 革兰氏阴性 败血症
• 寄生虫感染，如 疟疾
• Paroxysmal nocturnal hemoglobinuria (PNH)
• 冲击

正常的结果

The normal range is 88 to 201 milligrams per deciliter (mg/dL) (0.88 to 2.01 g/L).

Note: Normal value ranges may vary slightly among different laboratories. Talk to your provider about the meaning of your specific test results.

The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.

异常结果意味着什么

Increased complement activity may be seen in:

• 癌症
• 溃疡性结肠炎

Decreased complement activity may be seen in:

• Bacterial infections (especially Neisseria)
• 肝硬化
• 肾小球肾炎
• 肝炎
• 遗传性血管性水肿
• 肾移植 拒绝
• 狼疮肾炎
• 营养不良
• 系统性红斑狼疮
• Rare inherited complement deficiencies
  
  

风险

风险 associated with having blood drawn are slight, but may include:

• 大出血
• Fainting or feeling lightheaded
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

注意事项

The complement cascade is a series of reactions that take place in the blood. The cascade activates the complement proteins. The result is an attack unit that creates holes in the membrane of bacteria, killing them. C3 attaches to bacteria 和 kills them directly.

参考文献

阿特金森摩根大通. 疾病中的补体系统. 参见:Goldman L, Schafer AI主编. Goldman-Cecil医学. 26日艾德. Philadelphia, PA: Elsevier; 2020:chap 44.

Bean KV, Massey HD, Gupta G. Mediators of inflammation: complement. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis 和 Management by Laboratory Methods. 24日艾德. Philadelphia, PA: Elsevier; 2022:chap 48.

Sullivan KE, Grumach AS. 补体系统. In: Burks AW, Holgate ST, O'Hehir RE, Broide DH, et al. eds. Middleton's Allergy: Principles 和 Practice. 9日艾德. Philadelphia, PA: Elsevier; 2020:chap 8.