Surveillance methods - HTLV

Prior to 2002, surveillance of HTLV in England and Wales was through laboratory reporting coordinated by the Public Health Laboratory Service, Central Public Health Laboratory, and clinician reporting through the HTLV European Research Network (HERN). At the beginning of 2002, responsibility for the coordination of HTLV surveillance activities in England and Wales was transferred to what is now the HIV/AIDS Reporting Section of the HPA Centre for Infections. The current surveillance system is shown in the figure.

Laboratory reports of new HTLV diagnoses are received from the HPA Sexually Transmitted Blood Borne Virus Laboratory (SBVL) at Colindale and from the Department of Virology at Kings' College Hospital, London. These two specialist laboratories confirm the diagnosis of the great majority of individuals diagnosed with HTLV in in England and Wales at some stage. Information collected from laboratory reports is illustrated in table 1.

When the laboratory result is returned from Colindale to the requesting laboratory, a surveillance form is enclosed, to be forwarded to the attending clinician. Clinicians are asked to complete these forms and return them to CFI. These forms contain more detailed clinical information than laboratory reports, as illustrated in table 1.

An additional source of clinician reports is the NHS Blood and Transplant (NHSBT). The NHSBT began testing all blood donations in England and Wales for HTLV in August 2002. HTLV infections in blood donors are monitored through the NHSBT/HPA CFI infection surveillance system. This system collects information on the number of donations made, age and sex of donors, and in terms of HTLV, the numbers of HTLV infected donors detected. Additional characteristics of HTLV-infected donors that are collected include the history of probable exposures to infection and ethnicity. This information is passed on to the enhanced national HTLV surveillance system. Since most HTLV-infected donors will have donated before, the NHSBT has begun a lookback exercise to identify any recipients of potentially HTLV infectious donations transfused prior to August 2002. This provides a unique opportunity to recruit these people (donor and recipients) and their families to a HTLV National Register for long-term follow up in order to investigate the clinical course of HTLV infection. The HTLV National Register is a research study co-ordinated by NHSBT, HPA CFI and St Mary's.

All reports made to the routine HTLV surveillance system are matched with both the historic and current datasets to ensure that they are new HTLV diagnoses. Matching requires the use of the 'soundex' code (a unique identifier generated from the surname but which cannot be converted back to the name), gender, and date of birth, as well as other variables.

Figure 1 - Schematic diagram of HTLV surveillance system since 2002

Table 1 - An example of variables collected on laboratory and clinician reports of new
HTLV diagnoses since 2002