AFP

Reference value

10ng/mL or less (EIA method)

High levels in patients with liver cancer

AFP is one of the glycoproteins that are produced in abnormally large amounts by liver cells when they become cancerous, and is measured when examining liver cancer. AFP increases in the blood of many people with liver cancer, showing values ​​several tens to several hundreds times higher than the normal value.

The AFP value continues to rise as liver cancer progresses, and can reach several thousand times the normal value. The AFP value, which temporarily decreases with treatment, will rise again if the cancer recurs, progresses, or metastasizes to other sites, making it useful for monitoring the progress after treatment.

Positive results for cancer other than liver cancer

In cases of cirrhosis or hepatitis (fulminant hepatitis or chronic hepatitis exacerbation), AFP may become positive when liver cells are regenerating strongly. However, the increase is only a few times, and it is rare for the increase to continue over time. Pancreas water In cancers such as pancreatic cancer, biliary tract cancer, and colon cancer, the test result may sometimes be positive, but the levels are not as high as in liver cancer.

Measures based on test results

If AFP is above the standard value, first suspect hepatocellular carcinoma and measure other tumor markers (PIVKA-II) that are positive in hepatocellular carcinoma, and perform abdominal ultrasound (→see reference) or abdominal CT (→see reference) to confirm the presence of a tumor. Many hepatocellular carcinomas develop from liver cirrhosis, and people who are positive for hepatitis C virus (→see reference) are particularly at high risk of developing hepatocellular carcinoma, so AFP should be checked regularly (every 6 months) during follow-up of liver cirrhosis, and if it exceeds the standard value even slightly, a detailed examination should be performed.

On the other hand, when there is no cirrhosis and no hepatocellular carcinoma, detailed examinations for malignant tumors in other organs are also necessary.

The main diseases suspected are

◆ High levels → Hepatocellular carcinoma, other cancers, liver cirrhosis, fulminant hepatitis, chronic hepatitis, pregnancy, congenital biliary atresia, etc.

The common term used by doctors is "AFP," which stands for alpha-fetoprotein.

Source: Hoken "4th Edition: A book that explains the tests you will receive at the hospital" Information about the 4th Edition: A book that explains the tests you will receive at the hospital

基準値

10ng/mℓ以下（EIA法）

肝臓がんで高値に

　AFPは、肝細胞ががん化したとき、その細胞が異常にたくさんつくり出す糖蛋白のひとつで、肝臓がんを調べるとき測定します。AFPは肝臓がんのかなりの人の血液中で上昇し、基準値の数10倍から数100倍の高値を示します。

　AFPの値は肝臓がんの進行とともに上昇を続け、基準値の数千倍になることもあります。治療によって一時低下したAFPの値が、その後の経過でがんが再発したり進行したり、また、ほかへ転移したりすると再び上昇するため、治療後の経過観察にも有用になります。

肝臓がん以外でも陽性に

　肝硬変や肝炎（劇症肝炎や慢性肝炎増悪期）で、肝細胞の再生が強いときにAFPは陽性になることがあります。しかし、上昇度は数倍以内であり、経時的に上昇を続けることは稀です。肝臓がん以外のがん（胃がん、膵すい臓がん、胆道がん、大腸がんなど）でも、ときに陽性となりますが、肝臓がんほど高値ではありません。

検査値からの対策

　AFPが基準値以上を示したら、第一に肝細胞がんを疑い、肝細胞がんで陽性を示すほかの腫瘍マーカー（PIVKA－Ⅱ）を測定したり、腹部超音波（→参照）や腹部CT（→参照）を行って腫瘍の存在を確認します。肝細胞がんの多くは肝硬変から移行することが多く、とくにC型肝炎ウイルス（→参照）陽性者は肝細胞がんを発症するハイリスク群であるため、肝硬変の経過観察において定期的（6カ月ごと）にAFPをチェックし、基準値を少しでも上回るようなら精密検査を行います。

　一方、肝硬変がなく肝細胞がんも認められないときは、ほかの臓器の悪性腫瘍の精密検査も必要です。

疑われるおもな病気などは

◆高値→肝細胞がん、その他のがん、肝硬変、劇症肝炎、慢性肝炎、妊娠、先天性胆道閉鎖症など

医師が使う一般用語
「エーエフピー」＝α-fetprotein（アルファ-フェト蛋白）の略AFPから

出典　法研「四訂版 病院で受ける検査がわかる本」四訂版 病院で受ける検査がわかる本について　情報