Diagnostic and immune status serologic assays are performed for various rickettsial and viral agents. Assay methods vary depending upon the specific test requested.
Only serum and CSF may be submitted for serologic testing. Specimens submitted to the Virology/Serology Unit must be accompanied by a fully completed submission Special Serology Form #3445 (PDF, 113 KB). Failure to supply the requested patient information may result in significantly delayed specimen testing. Tests must be requested by name. Nonspecific requests for "viral studies" or "viral serologies" will not be accepted. Consult with the laboratory if there is a question as to which test is appropriate.
Screening for immunity to measles, mumps, rubella, and varicella zoster is not available on a routine basis. Exceptions to this policy apply to local health departments only and include the following:
Specimens submitted for testing that are not labeled with correct patient identification information will not be tested. Patient identification includes full first and last name and either SSN, date of birth, or other unique identifier. Specimens which, for any reason, are deemed unsuitable or inappropriate for serologic testing will not be tested. Rejected specimens will be properly stored for ten days pending verbal and/or written notification of the submitter. Unless alternate arrangements are initiated by the submitter upon notification of specimen rejection, the specimen will be discarded at the end of the holding period.
To collect serum, draw blood into a red top vacuum tube allowing the tube to fill completely. Let stand for 30 minutes to ensure complete clotting of the blood. Centrifuge for 5-10 minutes at 1000-1500 x g. Transfer the serum to a plastic screw capped vial. Hemolyzed, icteric, or lipemic serum may be unacceptable for certain serologic assays.
Clearly label each vial of serum with the patient's full first and last name, either SSN, date of birth, or other unique identifier, and the date collected if paired sera are submitted. Complete a Special Serology Form #3445 (PDF, 113 KB) submission form specifying all required patient information and which infectious agents are suspected.
The serodiagnosis of a current or recent infection generally requires the simultaneous testing of paired serum samples, principally, acute and convalescent serum samples. The acute serum should be collected no later than 3-5 days after the onset of illness. The convalescent serum should be collected 2-4 weeks after onset. Where paired sera are advised or required, it is to the advantage of both the submitter and this laboratory if the acute serum is stored frozen by the submitter until the convalescent serum is collected. Both serum samples may be submitted with one submission form.
Serological diagnosis of mumps between acute and convalescent sera can be made by demonstrating a four-fold or greater rise in titer. For certain agents such as measles and rubella, specific IgM assays on a single acute serum specimen may provide evidence of a recent infection. Additionally, single "high" antibody titers to viral and rickettsial agents may be considered presumptive evidence of recent infection. Immune status determinations require a single serum sample only and should be clearly designated on the request form. Antibody determinations on cerebrospinal fluid may be of value in diagnosing viral encephalitis and other central nervous system diseases. Cerebrospinal fluids for serologies should always be accompanied by a serum collected the same day.
Properly identified vials of patient sera along with the completed submission forms should be sent in the blue colored specimen mailers labeled SPECIAL SEROLOGY. For detailed shipping instructions using the double mailers, see Packing Instructions Using Outer Baggie (PDF, 4.6 MB). Ship at ambient temperature by the State Courier or U.S. Mail. Specimens should be shipped immediately and should arrive in the laboratory within 48 hours of collection. Specimens may be shipped refrigerated or at ambient temperature. If transport to the laboratory is to be delayed, specimens can be refrigerated up to seven days or frozen.
Serum transport tubes and blue colored specimen mailers are available through the NCSLPH online supply ordering system at this website. Both Special Serology Form #3445 (PDF, 113 KB) and DHHS Rubella Serology Form #1188 (PDF, 79 KB) may be downloaded and printed from this website.
Assay turn-around-time after receipt of the specimen(s), methodology used, serum requirements, and test interpretation vary considerably between tests. The following chart lists the special serologic assays performed by this Unit. A brief statement of the "normal" values for each assay is given under the heading "Negative Reference Range". The test method, specimen requirements and turn-around-times are also listed for each assay performed.
|Test||Test Method||Negative Reference Range||Specimen Requirements||Turn-Around-Time|
|Ehrlichia chaffeensis, IgG||IFA-Quan||<1:64||2 mL serum; PSA||5 working days|
|Measles, IgM||IFA-Qual||Interpreted by report||2 mL serum||1 working day|
|Measles, IgG||IFA-Qual||Interpreted by report||2 mL serum||3 working days|
|Mumps, Diagnostic IgG||IFA-Quan||Interpreted by report||2 mL serum; PSA||3 working days|
|Rickettsia rickettsii (RMSF), IgG||IFA-Quan||<1:64||2 mL serum; PSA||5 working days|
|Rickettsia typhi (Typhus), IgG||IFA-Quan||<1:64||2 mL serum; PSA||5 working days|
|Rubella, Immune Status IgG||EIA-Qual||Interpreted by report||2 mL serum||2 working days|
|Rubella IgM||EIA-Qual||Interpreted by report||2 mL serum||1 working day|
|Varicella zoster, IgG||IFA-Qual||Interpreted by report||2 mL serum||3 working days|