To the Editor: In reference to the letter by Kennedy et al, reporting two patients who tested positive to human T-lymphotropic virus I/II (HTLV-I/HTLV-II) antibodies after administration of the intravenous immunoglobulin, Octagam (Octapharma Australia, Sydney, NSW),1 the Therapeutic Goods Administration (TGA) would submit that:

• This product was accepted for review by the TGA at a time when plasma products sourced from overseas had to demonstrate superiority over the local product. This requirement was fulfilled by Octagam on grounds that included pathogen safety issues.

• HTLV-I and HTLV-II are entirely cell-associated viruses and are thus irrelevant to the safety of plasma derivatives. They are in a group of pathogens for which risks, implied by epidemiological factors, apply to cellular but not to plasma products. Another common example is malaria. The Australian plasma pool includes donations from individuals who are at risk of transmitting malaria, so their cells are not used but their plasma is used for fractionation. This situation is well understood and managed by regulators, none of whose standards internationally include the need to test plasma donors for HTLV-I/HTLV-II infection. As the bulk of Australia’s fractionation pool is derived as a by-product of whole blood, blood is tested for HTLV-I/HTLV-II in this country, but it is not a mandatory requirement in Australia or anywhere else.

• The exclusion of antibody from the plasma pool, as occurs for HTLV-I/HTLV-II in Australia, may actually lead to the loss of potentially protective antibodies, which may well have a therapeutic effect in protecting patients from HTLV-I/HTLV-II infection.2 Such considerations apply, for example, in the requirements of the Food and Drug Administration in the United States for source plasma for fractionation. The requirements take care to allow the inclusion of antibody-positive units for some viruses that would be excluded from blood transfusion.

• The incident referred to by Kennedy et al was appropriately reported to the TGA’s Adverse Drug Reactions Unit, which concluded that this was not an adverse event.

• A Northern Territory Government document on HTLV reports: “In Central Australia the prevalence of HTLV-I is estimated to be up to 14%, compared to 4.7% in the Northern Territory cattle country . . .”3 The residual risk of transmission of HTLV-I/HTLV-II infection, while low,4 clearly varies across the potential donor population, and comparisons that are irrelevant in relation to the safety of specific products would appear to be unwise.

• It is recommended that practitioners seeking to assess causality in putative infectious disease transmission by plasma products follow rigorous scientific processes, such as those recommended by the German regulatory authority.5