Infectious mononucleosis (전염 단핵구증) 진단

Infectious mononucleosis (전염 단핵구증) 진단

1. 비정형 림프구

발병 초 2주동안 백혈구 증가를 보이는데, 이 중 50% 는 림프구이며 약 20% 는 비정형 림프구 이다. (정상 림프구보다 크며, Vacuolated cytoplasm 과 Elongated, indented nucleus 에 굵은 염색질이 나타난다.)

2. Heterophil antibody (Paul-Bunnell test, Davidsohn-Henry test)

양의 적혈구를 응집시키는 이종 항체를 검사한다. (말의 적혈구는 양보다 민감도가 증가한다.)

The heterophile test is used for the diagnosis of IM in children and adults. In the test for this antibody, human serum is absorbed with guinea pig kidney, and the heterophile titer is defined as the greatest serum dilution that agglutinates sheep, horse, or cow eη吨hrocytes.

The heterophile antibody does not interact with EBV proteins. A titer of =>40 is diagnostic of acute EBV infection in a patient who has symptoms compatible with IM and atypical Iymphocytes. Tests for heterophile antibodies are positive in 40% of patients with IM during the first week of illness and in 80-90% during the third week. Therefore, repeated testing may be necessary, especially if the initial test is performed early. Tests usually remain positive for 3months after the onset of illness, but heterophile antibodies can persist for up to 1 year. These antibodies usually are not detectable in children

<5 years of age, in the elderly, or in patients presenting with symptoms not typical of 1M.

The commercially available monospot test for heterophile antibodies is somewhat more sensitive than the classic heterophile test. The monospot test is -75% sensitive and -90% specific compared with EBV-specific serologies (see below) . False-positive monospot results are more common among persons with connective tissue disease, Iymphoma, viral hepatitis, and malaria.

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3. EBV 특이 항원에 대한 항체 검사

(1) VCA (Viral capsid antigen) 에 대한 IgG : 발병초에 나타나며, 이미 최고치를 보인다. 항체가는 평생 지속된다.

(2) VCA (Viral capsid antigen) 에 대한 IgM : 의미있는 진단적 가치가 있으나, 혈청 내의 RA factor 로 인해 거짓 양성이 나올 수도 있다. 몇 개월간 지속되는 항체이다.

(3) EA (Early antigen complex) : R (restricted) 와 D (diffuse) 의 두 성분으로 따로 측정되기도 한다. 바이러스 증식과 연관이 있으며, 감염 초기부터 나타나 6개월~수년 후에 사라진다.

(4) EBNA (EB nuclear antigens) : 잠복감염 항원으로 이 항체가 가장 늦게 (증상 시작 후 3~4개월) 나타나 영구히 지속되기 때문에 이 항체의 존재 여부에 따라 EBV 초회 감염과의 감별 및 발생 시기를 알 수 있다.

EBV-specific antibody testing is used for patients with suspected acute EBV infection who lack heterophile antibodies and for patients with atypical infections. Titers of IgM and IgG antibodies to viral capsid antigen (VCA) are elevated in the serum of more than 90% of patients at the onset of disease.

IgM antibody to VCA is most useful for the diagnosis of acute IM because it is present at elevated titers only during the first 2-3 months of the disease; in contrast, IgG antibody to VCA is usually not useful for diagnosis of IM but is often used to assess past exposure to EBV because it persists for life.

Seroconversion to EBNA positivity also is useful for the diagnosis of acute infection with EBV. Antibodies to EBNA become detectable relatively late (3-6 weeks after the onset of symptoms) in nearly all cases of acute EBV infection and persist for the lifetime of the patient. These antibodies may be lacking in immunodeficient patients and in those with chronic active EBV infection.

Titers of other antibodies also may be elevated in IM; however, these elevations are less useful for diagnosis. Antibodies to early antigens are detectable 3-4 weeks after the onset of symptoms in patients with IM. About 70% of individuals with 1M have early antigen diffuse (EA-D) antibodies during the illness; the presence of EA-D antibodies is especially likely in patients with relatively severe disease. These antibodies usually persist for only 3-6 months. Levels of EA-D antibodies are

also elevated in patients with nasopharyngeal carcinoma or chronic active EBV infection. Early antigen restricted (EA-R) antibodies are only occasionally detected in patients with 1M but are often found at elevated titers in patients with African Burkitt's Iymphoma or chronic active EBV infection. IgA antibodies to EBV antigens have proved useful for the identification of patients with nasopharyngeal carcinoma and of persons at high risk for the disease.

끝. 

2018. 7. 15 - SJH