Serological Analysis Group Tests
The Serological Analysis Group aids submitters in the diagnosis of many diseases by detecting antibodies to those diseases. The following table lists the tests performed by the Diagnostic Serology and HIV/STD Teams. There are links to descriptions of the diseases, as well as links to descriptions of the assays used.
Note: External links to other sites are intended to be informational and do not have the endorsement of the Texas Department of State Health Services. These sites may also not be accessible to people with disabilities.
Effective immediately, Toxoplasma and Bartonella IgG Antibody tests will no longer be offered at the DSHS Laboratory due to unavailability of reagents. You can contact commercial laboratories for Toxoplasma and Bartonella antibody testing, if needed.
Type of Assay
Frequency of Testing
|Brucellosis||Agglutination||A single titer >= 1:160 is evidence of a prior infection, but does not confirm that it was recent. The most convincing evidence of recent infection is a 4 fold rise in titer between an acute and convalescent serum.||Weekly|
|Chagas||Enzyme Immunoassay (EIA)||All specimens submitted for Chagas IgG serologic screening will be tested using two different enzyme immunoassays, both designed to detect antibodies to Trypanosoma cruzi, the causative agent of Chagas disease.
Results from both assays are considered when determining the final result interpretation. All specimens with presumptive positive, equivocal, and inconclusive results will be forwarded to the Centers for Disease Control and Prevention (CDC) for confirmatory testing.
A presumptive positive result indicates that antibodies to Trypanosoma cruzi were detected for both assays.
A negative result indicates that antibodies to Trypanosoma cruzi were not detected for both assays. There is a high probability of non-infection.
An equivocal result indicates that the presence or absence of antibodies to Trypanosoma cruzi could not be established with either assay.
An inconclusive result indicates that results between the two assays did not agree. Additional testing is required to resolve the discordant results.
|Dengue Fever||Enzyme Immunoassay (EIA)||A 4 fold change in antibody titer or the presence of Dengue-specific IgM in CSF confirms a recent infection. Reactive IgM result in a single serum sample is considered only presumptive evidence of recent infection, because the IgM can be detected for months and up to a year after Dengue infection. Serological cross-reactions with other flaviviruses (SLE and WN) preclude definitive diagnosis without confirmation by serum neutralization from the CDC.||Weekly|
|Ehrlichia||Immunofluoresence (IFA)||A 4 fold or greater rise in titer between acute and convalescent sera, collected four weeks apart, is evidence for infection with Ehrlichia.||Twice weekly|
|Hantavirus||Enzyme Immunoassay (EIA)||A 4 fold rise in IgG antibody titer or the presence of IgM in acute-phase sera is diagnostic for hantaviral disease.||Weekly|
|Hepatitis A Antibody||Enzyme Immunoassay (EIA)||Measures the total antibodies to HAV (IgG, IgM and IgA) and is positive in acute hepatitis A and remains positive indefinitely. The total antibody test to HAV is used to determine previous exposure to HAV and assess immune status.||As needed|
|Hepatitis A IgM||Enzyme Immunoassay (EIA)||A positive test is indicative of recent infection with HAV.||As needed|
|Hepatitis B core Antibody||Enzyme Immunoassay (EIA)||In the absence of HBsAg and antibody to HBsAg, a positive anti-HBc is a serological marker of recent infection. In the presence of antibody to HbsAg, a positive anti-HBc is a serological marker of past exposure.||Twice weekly|
|Hepatitis B surface Antibody||Enzyme Immunoassay (EIA)||Antibody to HBsAg with or without anti-HBc, specifies immunity against reinfection. Antibody to HBsAg without anti-HBc develops in persons who receive hepatitis B vaccine.||Twice weekly|
|Hepatitis B surface Antigen||Enzyme Immunoassay (EIA)||Repeatedly high reactive sera are not confirmed by a confirmatory test at TDSHS Laboratory. Low reactive results are further tested for the presence of HepBcore antibodies.||Daily|
|Hepatitis C Antibody||Enzyme Immunoassay (EIA)||Sera positive for HCV by EIA method should be confirmed by additional supplementary test.||Three times weekly|
|Hepatitis C RNA, Quantitative NAAT||RNA Quantification by Real-Time Transcription Mediated Amplification.||This test can confirm hepatitis C virus (HCV) infection by detecting and calculating the concentration of HCV RNA in serum and plasma. Concentrations are reported in IU/mL for this assay.
A "Not Detected" result indicates that HCV RNA was not detected in the patient’s serum or plasma.
A result of <10 IU/mL indicates that HCV RNA was detected but not quantified. HCV RNA is below the Lower Limit of Quantification (LLoQ) for this assay.
A result between 10 IU/mL and 25 IU/mL indicate that HCV RNA was detected and quantified.
A result between 25 IU/mL and 100,000,000 IU/mL indicates a current HCV infection and HCV RNA was detected and quantified.
A result of >100,000,000 IU/mL indicates a current HCV infection and HCV RNA was detected but was above the Upper Limit of Quantification (ULoQ) and could not be quantified.
An "Invalid" result occurs when an error occurred during testing.
|HIV-1 RNA, Quantitative NAAT||RNA Quantification by Real-Time Transcription Mediated Amplification.||This test can confirm Human Immunodeficiency Virus type 1 (HIV-1), infection by detecting HIV-1 RNA in both serum and plasma.
Quantitative results are possible for plasma only. Serum testing provides qualitative results only. Concentrations are reported in copies/mL for this assay.
A "Not Detected" result indicates that HIV-1 RNA was not detected in the patient’s plasma.
Diagnostic qualitative interpretation:
Non-reactive for HIV-1
Diagnostic qualitative interpretation:
Reactive for HIV-1.
Diagnostic qualitative interpretation:
Reactive for HIV-1.
Reactive for HIV-1.
|Human Immunodeficiency Virus (HIV)
||Enzyme Immunoassay (EIA)||The HIV COMBO procedure for serum (enzyme immunoassay) includes testing for HIV-2, HIV-2 and the p24 antigen. All HIV reactive specimens on serum are confirmed with the HIV Multispot. Oral Fluid and DBS specimens are tested for HIV-1 and confirmation is by Western Blot. Specimens that are found to be repeatedly reactive on the EIA must be confirmed using a more specific test – the Multispot for serum or the Western Blot for oral fluid or DBS.||Daily|
|Western Blot (WB)||The Western Blot also detects antibodies to HIV-1 present in human serum, oral fluid or DBS. If antibodies to any of the major HIV antigens are present in the specimen in sufficient concentration, bands corresponding to the position of one or more of the following HIV proteins (p) or glycoproteins (gp) will be seen on the nitrocellulose strip: p17, p24, p31, gp41, p51, p55, p66, gp120, gp160 (the number refers to apparent molecular weight in kilodaltons). Interpretation is based on the presence or absence of these bands. A sample that is repeatedly reactive in the EIA and reactive in the Western Blot is presumed to be reactive for antibodies to HIV-1. Individuals with reactive tests should be referred for medical evaluation. A diagnosis of AIDS can only be made if an individual meets the case definition established by the CDC.||Twice weekly|
|Multispot Qualitative Immunoassay||The Multispot is a rapid test to detect and differentiate circulating antibodies to Human Immunodeficiency Virus Types I and 2 (HIV-1, HIV-2). This test is suitable for use in multi-test algorithms designed for statistical validation of an HIV screening test result or as part of an HIV-1/HIV-2 diagnostic testing algorithm that includes differentiation of HIV-1 and HIV-2 antibodies.||Daily|
|Legionnaire's Disease||Immunofluoresence (IFA)||A four-fold or greater rise in titer to 128 from acute-phase to convalescent-phase of illness is considered positive in a patient with pneumonia.||Twice weekly|
|Measles||Enzyme Immunoassay (EIA)||Measles specific IgM in a single sera or a four-fold or greater rise in titer between acute and convalescent phase sera taken at 7-14 day interval is the basis of diagnosis of acute infection. The presence of measles specific IgG antibody in a single serum indicates past infection or vaccination.||Twice weekly|
|Mumps||Enzyme Immunoassay (EIA)||Mumps specific IgM in a single sera by IFA or a four-fold or greater rise between acute and convalescent phase sera by EIA is presumptive evidence for infection with mumps virus. Cross-reactivity between mumps and parainfluenza virus exists, therefore, simultaneous testing for parainfluenza virus is recommended in atypical mumps cases.||Weekly|
|Plague||Hemagglutination||A titer of >1:10, in the absence of known recent plague-vaccine history or exposure is a presumptive diagnosis for plague. A single serum titer of >1:128 in the absence of vaccination, or a 4 fold rise in titer between paired sera, collected more than 2 weeks apart, is considered positive for a recent infection and must be reported to health authorities.||Weekly|
|Q Fever||Immunofluoresence (IFA)||A 4 fold or greater rise in titer between acute and convalescent phase sera is evidence for recent infection. In acute Q-fever infections, antibodies to the phase II antigen are usually higher than the antibody titer to phase I. In chronic Q fever infection, however, phase I titers eventually equal or exceed phase II titers. A single Q fever IFA titer >= 1:256 is evidence of a prior infection, but, it does not confirm that the infection was recent.||Weekly|
|Rocky Mountain Spotted Fever||Immunofluoresence (FI)||A 4 fold or greater rise in titer between acute and convalescent phase sera is convincing serological evidence of recent rickettsial infection.||Twice weekly|
|Rubella IgG||Enzyme Immunoassay (EIA)||A 4 fold or greater rise in antibody titer between paired acute and convalescent phase sera is confirmation of clinical rubella infection. The presence of rubella specific IgG antibody in a single serum specimen indicates prior infection and possibly immunity if the rubella specific IgG antibody titer is >=10 mIU/ml of serum.||Daily|
|Rubella IgM||Enzyme Immunoassay (EIA)||Presence of rubella-specific IgM antibodies is confirmation of clinical rubella infection.||Twice weekly|
|St Louis Encephalitis (SLE)||Enzyme Immunoassay (EIA)||A four-fold change in antibody titer or the presence of SLE-specific IgM in CSF confirms a recent infection. Reactive IgM result in a single serum sample is considered only presumptive evidence of recent infection, because the IgM can be detected for months and up to a year after SLE infection. Serological cross-reactions with other flaviviruses (WN and Dengue Fever) preclude definitive diagnosis without confirmation by serum neutralization from the CDC.||Weekly|
|Syphilis (Screen)||Multiplex Flow Immunoassay||Specimens tested for syphilis follow a reverse algorithm for diagnosis. If the specimen is reactive for Syphilis IgG it indicates a past or current infection with Syphilis. Confirmation is performed with the RPR (Rapid Plasma Reagin) Card and TP-PA (Treponema pallidum Particle Agglutination) test. The RPR is non-specific for syphilis and the TP-PA is specific for Treponema pallidum. Diagnosis is dependent on the interpretation of these three assay results.||Daily|
|Syphilis (Confirmation, RPR)||Rapid Plasma Reagin (RPR) Card||This is a confirmatory test for syphilis. A reactive test may indicate past or present infection with a pathogenic treponeme. A four-fold rise in titer on a repeat specimen may indicate an infection, a reinfection or a treatment failure. A four-fold decrease in titer in early syphilis usually indicates adequate syphilis therapy. False positive reactions can result from serum antibodies unrelated to syphilis infection; therefore, a reactive result should be confirmed by confirmatory treponemal tests. A nonreactive RPR card test and no clinical evidence of syphilis may indicate no current infection or an effectively treated infection, however, false negative results can be observed during primary syphilis, in secondary syphilis as a result of prozone reaction, and in some cases of late syphilis.||Daily|
|Syphilis (Confirmation, TP-PA)||Treponema Pallidum Particle Agglutination (TP-PA)||This is part of the testing algorithm to diagnose syphilis, and it is also a confirmatory test for syphilis. A reactive TP-PA test on a specimen that is also positive with a cardiolipin test suggests current or past infection with a pathogenic treponeme. All treponemal tests tend to remain reactive, probably for the life of the patient, therefore, they should not be used to evaluate response to therapy. However, false positive results can be seen. A nonreactive TP-PA test on a specimen that is reactive with a cardiolipin test is referred to as a biological false positive nontreponemal test and does not indicate syphilis. False-positive nontreponemal test results are seen in certain acute and chronic infections, following immunizations, in autoimmune disease and in intravenous drug users. A nonreactive TP-PA test on a specimen that is also nonreactive with a cardiolipin test usually indicates the absence of syphilis infection, except in incubating syphilis and in early primary syphilis, in which the TP-PA can be falsely nonreactive. For specimens that have an Inconclusive or Nonreactive interpretation with the TP-PA test we suggest submitting a second specimen in 3-4 weeks if clinically indicated.||Daily|
|Typhus||Immunofluoresence (IFA)||A 4 fold or greater rise in titer between acute and convalescent phase sera is convincing serological evidence of recent rickettsial infection.||Twice weekly|
|Tularemia||Agglutination||A single agglutination titer >1:128 or a 4 fold rise in titer between acute and convalescent phase sera, collected at least 2 weeks apart, and in the absence of previous vaccination history is diagnostic as positive for F. tularensis exposure.||Weekly|
|West Nile Virus||Enzyme Immunoassay (EIA)||A four-fold change in antibody titer or the presence of WN-specific IgM in CSF confirms a recent infection. Reactive IgM results in a single serum sample that is considered only presumptive evidence of recent infection, because the IgM can be detected for months after WN infection. Furthermore, serological cross-reactions with other flaviviruses (SLE and Dengue Fever) preclude definitive diagnosis without confirmation by serum neutralization from the CDC.||Weekly - by request only|