Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
Pathology Associates Of Lexington, P.A.
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         Erythema Infectiosum, Blood Test
      
Parvovirus B19 antibody test, serum

This is the virus causing "erythema infectiosum" (or "fifth disease") in  children. The virus replicates in the erythroid series of cells in the bone marrow and can cause a decrease in the reticulocyte count (production) to the point of a subsequent mild anemia. The typical blood test is an EIA serological test. Positives can be confirmed with testing by the Western blot method. [warning]

Situations Associated With Undetected/non-elevated (nr) Ab levels:

  • IgM should be non-reactive/absent except in acute or very early recurrent infection.

  • never-infected individual

  • previously infected but titer below standard delectability

Situations Associated With Elevated Ab levels:

  • erythema infectiosum (childhood skin rash)

  • aplastic anemia (rare) due to the virus

  • non-A non-B mild hepatitis (almost never jaundiced)

  • while some degree of joint pains is not uncommon with this infection, there are rare reports of a rheumatoid-arthritis-like condition with positive parvo serology

Pregnancy & Peripartem Implications:

  • congenital infection is rare (reactive IgM in cord blood)3, with a 9% mortality3

  • about 25% of cases of non-immunological fetal hydrops assoc. with reactive test3

Antibody Reactions:

  • IgM: detected within 3 days of symptom onset3, peaks in 30 days, usually undetectable after2-3 mo3....rarely persists to 6 months3

  • IgG: 

    • present in 10% of children <5 y/o3

    • present in 50% of adults3

    • rises upon infection and is detectable several years3

Interpretation:

  • IgG nr & IgM nr: means never infected (non-immune status) vs. past infection but subdetected ab levels (uncertain immune status)

  • IgG +, IgM nr: immune status, had a previous infection

  • IgG nr, IgM +: recent onset, primary infection

  • IgG +, IgM +: primary infection vs. reinfection

Parvo diseases:

  • erythema infectiosum (fifth disease)

  • parvo-induced pure aplastic anemia

  • persistent infection in patients with3:

    • immunosuppressed situations

    • chronic hemolytic anemia (sicklers, etc.)

References:

  1. Lexington Medical Laboratories, West Columbia, SC, procedure manual (primary references therein)

  2. Laboratory Medicine..., Howanitz and Howanitz, 1991, page 816

  3. Interpretation of Diagnostic Tests, Wallach, 2000, 7th Ed., pages 847.

  4. Carter, JB & Carter, SL  workshop handout  ca. 1980.

  5. Medical Microbiology [text], Jawetz, et. al, 22nd Ed., 1995.

  6. ABC's of Interpretive Laboratory Data [text], Seymour Bakerman, 2nd Ed., 1990.

(posted 2001)

 
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