补体成分4

定义

补体成分4 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 found in the blood plasma or on the surface of some cells.

The proteins work with your immune system 和 play a role in protecting from infection. They also help to remove dead cells 和 foreign material from the body. 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 C4.

选择的名字

C4

如何执行测试

血液从静脉中抽取. A vein from the inside of the elbow or the back of the h和 is most often 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

No special preparation is 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. When the complement system is turned on during inflammation, levels of complement proteins may go down. Complement activity may be measured to determine how severe a disease is or if treatment is working.

A complement test may be used to monitor people with an 自身免疫性疾病. For example, people with active systemic 红斑狼疮 may have lower-than-normal levels of the complement proteins C3 和 C4.

Complement activity varies throughout the body. 在患有 类风湿性关节炎, complement activity may be normal or higher-than-normal in the blood, but much lower-than-normal in the joint fluid.

正常的结果

Normal ranges for C4 is 15 to 45 milligrams per deciliter (mg/dL) (0.15 to 0.45 g/L).

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
• 昏厥或感到头晕
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

参考文献

Bean KV, Massey HD, Gupta Gaurav. 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.

Nadeau KC. Approach to the patient with allergic or immunologic disease. 参见:Goldman L, Schafer AI主编. Goldman-Cecil医学. 26日艾德. Philadelphia, PA: Elsevier; 2020:chap 235.

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.