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Test ID: HTLVL Human T-Cell Lymphotropic Virus Types I and II (HTLV-I/-II) Antibody Confirmation, Serum

Reporting Name

HTLV-I/-II Ab Confirmation, S

Useful For

Confirmatory detection of human T-cell lymphotropic virus types I and II (HTLV-I and HTLV-II)-specific IgG antibodies in human serum specimens that are consistently reactive by initial screening tests


Differentiating between HTLV-I- and HTLV-II-specific IgG antibodies

Clinical Information

Human T-cell lymphotropic virus types I and II (HTLV-I and HTLV-II) are closely related exogenous human retroviruses. HTLV-I was first isolated in 1980 from a patient with a cutaneous T-cell lymphoma, while HTLV-II was identified from a patient with hairy cell leukemia in 1982.


HTLV-I infection is endemic in southwestern Japan, the Caribbean basin, Melanesia, and parts of Africa, where HTLV-I seroprevalence rates are as high as 15% in the general population. In the United States, the combined HTLV-I and HTLV-II seroprevalence rate is about 0.016% among voluntary blood donors. About half of these infected blood donors are infected with HTLV-I, with most of them reporting a history of birth in HTLV-I-endemic countries or sexual contact with persons from the Caribbean or Japan. Smaller percentages report a history of either injection drug use or blood transfusion. Transmission of HTLV-I occurs from mother to fetus, sexual contact, blood transfusion, and sharing of contaminated needles. Two diseases are known to be caused by HTLV-I infection: adult T-cell leukemia or lymphoma (ATL) and a chronic degenerative neurologic disease known as HTLV-I-associated myelopathy (HAM) or tropical spastic paraparesis (TSP). Cases of polymyositis, chronic arthropathy, panbronchiolitis, and uveitis have also been reported in HTLV-I-infected patients.


HTLV-II is prevalent among injection drug users in the United States and in Europe, and more than 80% of HTLV infections in drug users in the United States are due to HTLV-II. HTLV-II also appears to be endemic in Native American populations, including the Guaymi Indians in Panama and Native Americans in Florida and New Mexico. HTLV-II-infected blood donors most often report either a history of injection drug use or a history of sexual contact with an injection drug user. A smaller percentage of infected individuals report a history of blood transfusion. HTLV-II is transmitted similarly to HTLV-I, but much less is known about the specific modes and efficiency of transmission of HTLV-II. The virus can be transmitted by transfusion of cellular blood products (whole blood, red blood cells, and platelets). HTLV-II infection has been associated with hairy-cell leukemia, but definitive evidence is lacking on a viral etiologic role. HTLV-II has also been linked with neurodegenerative disorders characterized by spastic paraparesis and variable degrees of ataxia.


Infection by these viruses results in the appearance of specific antibodies against the viruses that can be detected by serologic tests such as enzyme immunoassay For accurate diagnosis of HTLV-I or HTLV-II infection, all initially screening test-reactive results should be verified by a confirmatory test, such as Western blot or line immunoassay.


Negative confirmatory test results indicate the absence of both human T-cell lymphotropic virus types I and II (HTLV-I and HTLV-II)-specific IgG antibodies in serum.


A reactive screening (enzyme immunoassay) result with a negative or indeterminate confirmatory (line immunoassay) test result suggests either a false-reactive screening test result or a seroconverting HTLV infection. Repeat testing with a new specimen can clarify the final infection status. Persistently indeterminate confirmatory test results indicate absence of HTLV infection.


Positive results for HTLV-I antibodies indicate the confirmed presence of HTLV-I IgG antibodies in serum, based on 2 visible antibody bands that include gp21-I/-II band, or 3 or more bands, and the sum of the gp46-I and p19-I band intensity is greater than the gp46-II band intensity.


Positive results for HTLV-II antibodies indicate the confirmed presence of HTLV-II IgG antibodies in serum, based on 2 visible antibody bands that include gp21-I/-II band, or 3 or more bands, and the gp46-II band intensity is a) greater than the gp46-I band intensity and b) equal or greater than the sum of the gp46-I and p19-I band intensity.


Indeterminate results indicate the presence of gp21-I/-II band only or combination of any 2 bands without a detectable gp21-I/-II band. Patients with indeterminate test results with known risk factors for HTLV-I or HTLV-II infection should undergo repeat confirmatory antibody testing with a new specimen to determine final infection status.


Differentiation of HTLV-I and HTLV-II infection is not possible (ie, nontypeable HTLV antibodies) when the band intensity pattern does not meet the criteria of positive HTLV-I or HTLV-II antibody band intensity pattern.


Unreadable results indicate the presence of nonspecific background reactivity that is inhibiting the visualization of specific bands on the test strip. Repeat testing with a new specimen is recommended.


Invalid results indicate that nonspecific band reactivity is present. Submit another serum specimen for retesting, if clinically indicated.

Report Available

2 to 15 days

Day(s) Performed


Clinical Reference

1. Gessain A, Mahieux R: Tropical spastic paraparesis and HTLV-I associated myelopathy: clinical, epidemiological, virological, and therapeutic aspects. Rev Neurol (Paris). 2012 Mar;168(3):257-269. doi: 10.1016/j.neurol.2011.12.006

2. Mahieux R, Gessain A: Adult T-cell leukemia/lymphoma and HTLV-I. Curr Hematol Malig Rep. 2007 Oct;2(4):257-264. doi: 10.3390/v8060161.

3. Yamano Y, Sato T: Clinical pathophysiology of human T-lymphotropic virus-type I-associated myelopathy/tropical spastic paraparesis. Front Microbiol. 2012 Nov 9;3:1-10. doi: 10.3389/fmicb.2012.00389.

4. Murphy E, Roucoux D: The epidemiology and disease outcome of human T-lymphotropic virus type II. AIDS Rev 2004;6:144-154

5. Projetti FA, Carneiro-Projetti ABF, Catalan-Soares BC, Murphy EL: Global epidemiology of HTLV-I infection and associated diseases. Oncogene. 2005 Sep 5;24(39):6058-6068. doi: 10.1038/sj.onc.1208968. 

Method Name

Line Immunoassay (LIA)

Specimen Type

Serum SST

Ordering Guidance

This confirmatory assay should be ordered only on serum specimens that are consistently reactive by an antihuman T-cell lymphotropic virus 1 and 2 (anti-HTLV-I/-II) screening immunoassay. For an evaluation that includes screening and confirmation, order HTLVI / Human T-Cell Lymphotropic Virus Types I and II Antibody Screen with Confirmation, Serum.


For testing spinal fluid specimens, order HTLLC / Human T-Cell Lymphotropic Virus Types 1 and 2 (HTLV-1/-2) Antibody Confirmation, Spinal Fluid.

Necessary Information

Date of collection is required.

Specimen Required

Collection Container/Tube: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Centrifuge blood collection tube per collection tube manufacturer's instructions (eg, centrifuge and aliquot within 2 hours of collection for BD Vacutainer tubes).

2. Aliquot serum into plastic vial.

Specimen Minimum Volume

0.2 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum SST Frozen (preferred)
  Refrigerated  7 days

Reference Values


Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
HTLVL HTLV-I/-II Ab Confirmation, S 55162-2


Result ID Test Result Name Result LOINC Value
83277 HTLV-I/-II Ab Confirmation, S 22362-8
23898 HTLV-I/-II Bands 61112-9
23899 HTLV-I/-II Discrimination 77744-1
Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-Demyelinating-Diseases, mml-CNS-Infections, mml-Pediatric, mml-Spinal-Cord