Also Known As
Human T-Lymphotropic Virus
HTLV-1/2 Antibodies
HTLV-1/2 by PCR
Formal Name
Human T-Lymphotropic Virus Types 1/2 Antibodies; Human T- Lymphotropic Virus Types 1 and 2 by PCR
This article was last reviewed on
This article waslast modified on
11 February 2018.
At a Glance
Why Get Tested?

Antibodies (serology): To determine whether someone is infected with HTLV, either as a general screen, following potential contact with the virus, or as part of an investigation into the cause of a person’s illness (for example leukaemia or neurological disorders).

Molecular Tests: To confirm diagnosis when antibody tests are inconclusive, to assess risk of development of HTLV-associated complications; to aid diagnosis of HTLV-associated diseases; to monitor infection and treatment.

When To Get Tested?

When you have signs or symptoms that suggest that you may have an HTLV-associated condition, especially when you have identified risk factors; rarely when you have donated blood and been told that you are positive for HTLV

Sample Required?
  • Blood taken via a venepuncture from the arm (usual - almost always this is the sample taken)
  • Cerebrospinal fluid taken from the lower back via a lumbar puncture (uncommon)
  • Biopsy of abnormal tissue e.g. a lymph node or skin (uncommon)
Test Preparation Needed?

No special patient preparation is required for these tests

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you will be able to access your results online.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, gender, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

What is HTLV and how is it distributed in the world?
HTLV is a virus that infects humans and persists in the body for life. The virus infects the T-lymphocytes of the human host. T-lymphocytes are a type of white blood cell. Following infection there are three differing events, each of which contribute to the persistence of the virus in the host: 1) the virus spreads from the infected cell to other uninfected cells; 2) the virus causes the infected cells to multiply; 3) the virus persists in the infected cell silently for long periods.

Thus far four types of HTLV have been discovered which infect humans namely HTLV-1, HTLV-2, HTLV-3 and HTLV-4. HTLV-1 is the virus of major concern with the widest global distribution and the most disease complications. HTLV-2 is also relatively common in some regions/population groups but rarely causes disease. These two are therefore the HTLVs of principle concern. HTLV-3 and HTLV-4 are rare infections with no associated diseases yet reported.

On a global perspective, 5 to 10 million people are estimated to be infected with HTLV-1 with an uneven geographic distribution. There is only an incomplete picture of the prevalence of HTLV-1 infection but the existing data suggest that it is endemic with a high prevalence (considered as more than 1% of the population infected) in certain regions of the world: Japan, Caribbean islands, some African countries (especially West Africa), most countries of South America and certain regions of Oceania particularly Melanesia and the Northern Territory of Australia. HTLV-1 has also been reported in Romania and in some countries of the Middle-East. In Western Europe and North America the prevalence of HTLV-1 is considered low, but there are multiple pockets with higher prevalence within these low prevalence regions, which makes HTLV screening within them a higher priority.

The prevalence of HTLV-2 is estimated to be around 800,000 globally with the highest number in the United States followed by Brazil. The European HTLV-2 population is estimated to be between 20,000 and 40,000. HTLV-2 is endemic among the Amerindian populations and the pygmy populations in Central Africa.

Less is known about the epidemiology of the recently discovered HTLV-3 and HTLV-4, but these are simian viruses transmitted from monkeys to humans via bites or scratched in Central African (e.g. Cameroon). They have only been identified in a few subjects and have not yet been associated with human disease.

How is HTLV infection transmitted?
HTLV infection can be transmitted via 3 main routes.
1. Via unprotected sexual contact.
2. Via contaminated blood transfusions or blood products1, sharing contaminated needles and other injection equipment, or receiving an organ transplant from an infected donor.
3. HTLV virus can be passed from an infected mother to her baby mainly via breast feeding (predominantly with prolonged breast feeding beyond 6 months of age) and less commonly during the pregnancy (intra-uterine transmission).

1UK blood and tissue services test all blood donations and tissues for HTLV using serological techniques to ensure they are free of the infection. However, such screening is not mandatory in all countries including some European countries which may put recipients at risk. Additionally in the UK all blood products are subjected to removal of white blood cells (universal leucodepletion). This has been enforced since 1999, and further reduces the risk of transmission of infectious agents such as HTLV and cytomegalovirus to recipients.

What diseases does HTLV cause?
In the majority of infected individuals there is an asymptomatic carrier state (silent but ongoing infection), with only a small proportion (about 5 to 9%) developing disease associated with HTLV-1 during their lifetime.

HTLV-1 infection gives rise to two main disease entities: Adult T-cell leukaemia/lymphoma (ATLL) which is a form of blood cancer, and HTLV-associated myelopathy/tropical spastic paraparesis (HAM/TSP) which is a chronic inflammatory degenerative disease of the spinal cord leading to weakness of the lower limbs. ATLL occurs in 2 – 6% and HAM/TSP in approximately 3% of carriers.

In a smaller number of patients, other inflammatory conditions such as uveitis (inflammation of the eye), arthritis (inflammation of joints), myositis (inflammation of muscles), alveolitis (inflammation of lungs) and dermatitis (inflammation of skin) can be seen.

The HTLV-2 disease spectrum is less clear, but lung conditions, myelopathy (inflammation of the spinal cord) and dermatitis, have been reported.

Sometimes, as HTLV causes mild immunosuppression, patients may develop diseases caused by other infectious agents that are able to thrive in a host with a suppressed immune system (e.g. parasitic infections such as Strongyloides stercoralis).

What tests are performed?

  • Serology: Once individuals are infected with HTLV, their immune system starts producing antibodies that are specifically directed against the virus. By detection of these antibodies using laboratory tests, whether or not a person is infected with this virus can be determined. Using the development of antibodies to detect infection is called serology.
  • Molecular: Sometimes a test to detect the genetic material of the virus is used. This can be useful in situations such as having indeterminate serology (inconclusive antibody) test results or when antibodies to both HTLV-1 and HTLV-2 are detected. The measurement of HTLV-1 viral load in patients found to be infected is also useful to determine risk of disease and sometimes to aid with the diagnosis and treatment of an HTLV-1-associated disease. Detection and quantification of HTLV-genetic material is called molecular diagnostics.

How is the sample collected for testing?

Blood via venepuncture (inserting a needle into a vein of the arm).

Cerebrospinal fluid is collected via a lumbar puncture (inserting a needle into the lower back) to help with the diagnosis of HAM/TSP. This is only performed if HAM/TSP is suspected and is not required for the diagnosis of HTLV-1 or HTLV-2 infection per se.

Tissue for molecular test is obtained from a biopsy under local anaesthetic or at the time of an operation. This is only required if molecular testing of tissue is important to help with diagnosis of inflammation or ATLL.

Is any test preparation needed to ensure the quality of the sample?

No special preparations are needed for serology.

Blood samples for serological investigation can be sent to the laboratory in plain blood collection tubes or gel tubes (clotted blood).

The blood sample collected for molecular investigations needs to be collected into an EDTA (Ethylenediaminetetraacetic acid) blood tube. A minimum of 4mls should be obtained (adults).

CSF samples are collected into a plain universal container. Ideally at least 1ml is sent for HTLV diagnostic tests.

CSF samples and whole blood EDTA samples collected for molecular analysis must not be refrigerated or frozen, and must be sent to the laboratory within 24 hours, while being maintained at ambient temperature. Freezing CSF or whole blood kills the lymphocytes whilst refrigeration may also increase the rate of death of lymphocytes. Both can reduce the reliability of the molecular diagnostic tests.

Accordion Title
Common Questions
  • How is it used?

    Serological testing for HTLV infection
    Testing is carried out in order to determine whether or not an individual has HTLV infection.

    Detection of antibodies against HTLV using serological techniques is the main method of laboratory diagnosis of HTLV infection. These serological techniques include Enzyme Immunoassays (EIA or ELISA), particle agglutination tests and Western blot assays.

    Since HTLV-1 and HTLV-2 are established infections in humans, currently available routine tests can confirm infection only with HTLV-1 and HTLV-2, but not with new species such as HTLV-3 and HTLV-4. However an infection with a HTLV-3 or HTLV-4 may nevertheless yield a reactive test result during screening.

    Molecular testing for HTLV infection
    Molecular test methods such a Polymerase Chain Reaction (PCR) are not generally used as the first line for testing of specimens for HTLV infection, as a negative PCR test result obtained initially does not exclude the possibility of HTLV infection. However, molecular testing methods may be used to resolve an indeterminate serology test result, or aid the management of the patient.

    These tests are available only at highly specialized laboratories and include HTLV viral load testing, HTLV typing and HTLV clonal analysis.

    • HTLV viral load is used for diagnosing and monitoring of an infected person as the risk of HYLV-associated disease is related to viral load.
    • HTLV typing specifically identifies which HTLV species a person is infected with.
    • HTLV clonal analysis is used to facilitate diagnosis of ATLL, monitor treatment response of ATLL and as a means of early detection of relapse or confirming remission of the disease.
  • When is it requested?

    Testing is indicated for persons with a specific risk of HTLV infection. These include:

    • If you have come to the Europe from a high HTLV prevalence geographic area.
    • If you are from the second generation of a family who have come to the Europe originally from a high HTLV prevalence area.
    • If you have a family member who is diagnosed with HTLV.
    • If you have visited a high HTLV prevalence geographic area and had high risk contact that could put you at risk of infection.
    • If you have a sexual partner with known HTLV infection, or with one of the aforementioned risk factors for being infected with the virus,
    • If you have had unprotected sexual intercourse with multiple sexual partners.
    • If you are an injecting drug user, or have been in the past.
    • If you have a history of blood transfusion or organ transplantation outside of the UK.
    • If a child is born to a mother known to be infected with HTLV, the child needs to be tested. Children born to HTLV infected mothers should be tested by serology once they reach age 18 months.
    • If you have a combination of clinical features suggestive of an HTLV associated disease:
      • ATLL
        • fever
        • night sweats
        • fatigue
        • blood tests showing an increase in abnormal lymphocytes
        • enlarged lymph nodes
      • HAM/TSP
        • weakness of lower limbs
        • muscle spasms and contractions
        • muscle stiffness
        • lower back pain
        • urinary, bowel and sexual dysfunction
      • Other inflammatory conditions
        • uveitis
        • myositis
        • alveolitis
        • dermatitis

    All blood donors and organ donors are tested to ensure that they are HTLV-free before the blood or organs are transfused or engrafted respectively into the recipient.

  • What does the test result mean?

    A reactive serology screening test result may represent a false positive result, and therefore always needs to be confirmed in a more specific assay (usually Western blot).

    If the confirmatory test yields a positive result then the individual whose sample was tested is likely to have HTLV infection, either with or without disease complications.

    A negative result in contrast is considered conclusive evidence of absence of established infection.

    Antibody responses can take a few weeks to develop, and indeterminate results may therefore be seen in the context of recent infection. In such cases, testing may need to be repeated later (e.g. after 1 month) to obtain a conclusive result. The following table summarizes some typical results that may be seen with HTLV testing and their interpretation:

    Initial Antibody Testing (HTLV 1/2) Confirmatory Testing (Western blot) Additional Testing Likely Interpretation
    Non-reactive/Negative Not required Not required unless within the window period No infection
    Reactive Negative Repeat serology negative False positive on initial test
    Reactive Negative

    Repeat screening serology reactive

    Repeat Western blot negative

    False positive
    Reactive HTLV-1 confirmed Repeat serology reactive HTLV-1 infection
    Reactive HTLV -2 confirmed Repeat serology reactive

    HTLV-2 infection

    Reactive HTLV infection confirmed by not typed Molecular diagnostics to type infection

    HTLV untyped

    HTLV-1 or HTLV-2 infection by PCR

    Reactive HTLV-1 and HTLV-2 bands on Western blot

    Usually one band is stonger, and the weaker band represents cross-over reactivity.

    Molecular diagnostics to confirm type and exclude dual infection.

    HTLV untyped

    HTLV-1 or HTLV-2 infection by PCR

    Reactive Indeterminate

    Molecular test (PCR) positive or repeat

    Western blot positive for HTLV-1 or HTLV-2 on a subsequent sample

    HTLV-1 or HTLV-2 infection 

    Reactive Indeterminate

    Molecular test (PCR) negative and repeat Western blot still indeterminate on a subsequent sample

    Further follow-up required by serology and by molecular techinques

    HTLV indeterminate

  • Is there anything else I should know?

    HTLV is a lifelong infection and even without having symptoms you can pass the infection to others. Therefore it is essential that you take precautions to prevent the virus from being transmitted from yourself to others (see FAQs).

    HTLV-1 and HTLV-2 are closely related viruses and the screening assay detects both infections. It is therefore essential that further tests are performed to confirm infection and distinguish between the two viruses.

    HTLV screening tests are very sensitive (good at detecting infection) and specific (unlikely to give a positive result in an uninfected person). However false-positive reactions do occur and therefore all positive/reactive screening tests must be further investigated.

    Dual infection is uncommon. In situations where the Western blot suggests dual infection with HTLV-1 and HTLV-2, further confirmatory testing by a molecular method is required.

  • Should I be tested for HTLV-1/2 if I have some of the risk factors?

    If you believe that you have any risk factors for acquiring the infection, it is advised that this matter be discussed with your physician who will assess your risk and organize for the test to be done if appropriate.

  • I found out that I am positive for HTLV. What precautions should I take to avoid infecting others?

    Currently there are no vaccines to prevent acquisition of HTLV infection, or any approved drug therapies to reduce transmission of the virus to others. Preventive methods are therefore of utmost importance. You can protect your community and family from acquiring HTLV by taking the following measures:

    • By never donating any blood/tissue/sperm.
    • If you have a newborn baby, it is recommended not to breast feed. Arranging alternative nutrition for your baby should be done after discussing this with your healthcare provider.
    • By proper use of condoms – this will prevent HTLV transmission to your partner through sexual contact.
    • By not sharing needles or syringes with anyone. This measure not only prevents the spread of HTLV but also of other blood borne infections. 
    • If you believe that your partner or family member may have acquired HTLV infection from you, it is advisable for them to seek testing through their physician or healthcare provider.
    • Discussing the preventive measures with your physician or healthcare provider will give you better insight into preventing transmission.
  • Can I get HTLV-1/2 from donating blood?

    No. Since blood transfusion services use sterile needles exclusively for you, you cannot get HTLV infection from them.

  • The names HTLV and HIV look similar- are these diseases related?

    Although HTLV and HIV are part of the same large family of viruses called retroviruses, they belong to two distinct subfamilies that are distantly related. Both viruses infect cells of the human immune system but with quite different effects.

    HIV causes the infected lymphocytes to die, thereby causing a weakened immune system and eventually the acquired immune deficiency syndrome (AIDS). However, unlike for HTLV, there are now many drugs that can effectively control HIV infection and prevent and disease progression.

    HTLV either has little or no effect on the number of lymphocytes (carrier state), or causes them to increase in number, resulting in leukaemia or lymphoma. The host response to the virus sometimes causes inflammatory diseases such as spinal cord inflammation.

    Co-infection with both viruses (HTLV and HIV together) may cause a more serious form of suppressed immunity than with HIV infection alone and increase the likelihood of the spinal cord inflammation.

  • I had a potential exposure to HTLV. How soon should I get tested?

    Following infection with HTLV, it takes some time (weeks) for specific antibodies to reach detectable levels in blood (seroconversion). Since diagnosis relies on the detection of these specific antibodies, there is a time period during which recently infected individuals will have negative test results (the diagnostic window period).

    The HTLV window period for antibodies is variable. The best data are from persons who received HTLV infected blood products prior to the introduction of routine screening. In this situation seroconversion usually takes about 2 months.

    It is advisable to seek advice and assistance from your healthcare provider who can arrange for the test to be done if appropriate.