HTLV I & II 

Antibody, serum

In the USA, this is usually a situation where "positive" patients were found through required (since 1988) testing on blood donated to American Red Cross or other donor agencies. Positivity is almost always  related to recent "flu" vaccination or a cross reaction, see below. Unless there is reason to suspect actual HTLV disease, then retest at least 6 months beyond the date of the "flu" vaccination in order to prove that the test turned "negative". In this healthy donor population, less than 10% of those positives who test repeat-reactive/"positive" by such as EIA will test confirmatory positive by Western blot or recombinant immunoprecipitation assay (RIPA).

The human T-cell lymphotropic/leukemia viruses (retroviruses), HTLV-I and HTLV-II, are uncommon in the general U.S. population. HTLV-III (HIV-I) is the AIDS virus. The HTLV viruses can be transmitted by blood or intimate sexual contact, and can be passed from mother to child during pregnancy and through breast milk.

HTLV-I cases seem to be associated with travel to countries having endemic population positivity (Caribbean & Japan & sub-Saharan Africa).

HTLV-II appears to be most prevalent among IV drug users and persons who have multiple sex partners, genital ulcers, or a history of syphilis (and is endemic in certain native American populations). 

 There can always be test cross-reactions so that a person appears to be positive for either or both of HTLV I  HTLV II when only having been exposed to one of the agents. The agent with detectible presence of antigen by PCR, Western blot, or RIBA confirmatory testing is likely the actual offending organism in an active infection (but good confirmatory testing is not yet...9/04... licensed). [warning]

• Healthy persons who have never been infected.
• previously infected persons who did not mount a detectible level of Ab (may or may not be "immune")
• previously infected persons who have become seriously immunocompromised and cannot produce detectible Ab

 Elevated, reactive, or repeatedly positive results:

• you've had influenza ("flu") vaccine in past six months
• you've been infected by HTLV I or II (virus has an extremely long latency period...years...& only 4% risk of future ATL or HAM):
  1. HTLV I:
     • in adult T-cell leukemia or lymphoma (ATL): only 2.5% of repeatedly positive adults come down with this.
     • in tropical spastic paralysis (HTLV-associated myelopathy...HAM): only 2.4% of repeatedly positive adults come down with this.
  2. HTLV II:
     • in tropical spastic paralysis (HTLV-associated myelopathy...HAM): only 2.4% of repeatedly positive adults come down with this.
• you have some other cross-reacting antibody

References:

1. Practical Guide to Transfusion Medicine (BWD's office).
2. Carter, JB, NewsPath (our lab's newsletter), September 2004.