Gold (SST - Clot activator & gel)
2 ml blood
1 ml serum
If multiple viral serologies are being requested from the same specimen, the general rule is to collect a total of 2-4 ml of blood for every 2-3 tests ordered. A single serum specimen is required to determine the immune status of an individual or to test for viral-specific IgM antibodies. Paired sera specimens, collected two to three weeks apart, are required for the diagnosis of a current or recent viral infection when examining specimens for IgG antibody. Obtain the acute phase serum as soon as possible after the onset of illness. The most useful results are obtained by submitting acute and convalescent phase sera together to be tested simultaneously. Serological testing is not usually available for body fluids other than serum. However, in patients with viral neurologic disease (e.g., measles acute encephalitis or measles subacute sclerosing panencephalitis (SSPE)), cerebrospinal fluid (CSF) may be tested for measles antibody if paired with a serum specimen from the same date.
<0.9 - No measles (rubeola) IgG antibody detected
0.9-1.10 - Equivocal for measles (rubeola) IgG antibody
>1.10 - Positive for measles (rubeola) IgG antibody
Detection of virus-specific IgG in a single serum specimen indicates exposure to measles virus some time in the past or a response to vaccination. Demonstration of a seroconversion from a negative to a positive IgG antibody response between acute and convalescent sera collected 2-3 weeks apart can be diagnostic of recent or current measles infection. Negative IgG antibody results may exclude measles virus infection. For specimens with equivocal IgG antibody results, repeat testing of another specimen collected after a period of 14 days may be helpful.
Negative or no measles (rubeola) IgG antibody detected
Clinical Utility: Measles is an acute febrile illness characterized by cough, coryza, conjunctivitis, erythematous maculopapular skin rash, and an ascending (stepwise) fever to 39.5C. Complications include otitis media, pneumonia, croup, diarrhea, acute encephalitis, and subacute sclerosing panencephalitis (SSPE). Risk factors include age (<2 yrs and adults), nutritional status (malnourished), and immunocompromise. Localized epidemics still seen in the United States. Most cases are imported or linked to importation. Diagnosis of measles virus infection can be made by detection of virus-specific IgM and IgG antibody in serum, growth of the virus in culture from respiratory, eye, urine and whole blood specimens, and by rapid and direct detection of viral antigens in respiratory and eye specimens. At CHOP, it is recommended that a nasopharyngeal aspirate and conjunctival swab be submitted for rapid antigen detection and that serum be collected and submitted for measles-specific IgM and IgG serologies.
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